Tolerance to soil acidity of soybean (Glycine max L.) genotypes under field conditions Southwestern Ethiopia.

Soil acidity with associated low nutrient availability is one of the major constraints to soybean production in southwestern Ethiopia. Integrated use of lime and acid-tolerant crops is believed to reduce soil acidity and improve crop production. The experiment was conducted in the field condition of Mettu, southwestern Ethiopia during the 2017/18 main cropping season. The experiment comprised fifteen soybean genotypes and two soil amendment (lime and unlimed) treatments arranged in a split-plot design with three replications. For each treatment, four rows were planted per plot; data related to growth, root, nodule, and yield of the crop were collected at a necessary stage for each. Liming and genotype interaction had significantly (P = 0.01) affected all parameters considered except for hundred seed weight and root volume and were affected only by the main effects of genotypes and liming. A significant reduction for most parameters was found on lime-untreated soil than treated soil. Though some genotypes showed higher performance for root, growth parameters, and yield components under unlimed soils; however, gave higher yield and yield components, when grown on lime-untreated with an average yield reduction of 13.7%, due to soil acidity. The maximum grain yield of (1943.93 kg ha-1) was obtained under lime treated acid soil from PI567046A genotype; while the lowest (510.49 kg ha-1) were recorded from SCS-1genotype under the lime untreated acid soil. Genotype BRS268 showed higher yield (1319.83 kg ha-1) under lime untreated acid soil than lime treated acid soil (1143.47 kg ha-1) and showed less reduction percentage for a number of the nodules, root weight, and number of seeds per plant; while PI567046A showed high reduction percentage for yield, biomass, number of pod and seed per plant. A high difference was observed among the soybean genotypes for soil acidity tolerance, which might be further exploited by breeders for the genetic improvement of soybean. Genotype BRS268 had performed better than other tested genotypes under increased soil acidity. selection would be effective to improve soybean genotypes performance on acid soils and identify low Phosphorus tolerant genotype that helps smallholder farmers optimize soybean productivity on acid soils in the study area. HAWASSA-04 variety is the most tolerant among the tested materials. However, further study is required by considering additional genotypes to reach a conclusive recommendation.

Introduction

Land degradation, soil nutrient depletion and increasing soil acidity is challenging problem in south western Ethiopia. Soil acidity is one of the major problem that have profound effect on the productive potential of crops, such as soybean, because of low availability of basic cations, and excess and toxic levels of hydrogen and aluminum in exchangeable forms [1]. The major causes for soils to become acidic are high rainfall, leaching, acidic parent material, organic matter decay, and harvest of high yielding crops. Crop management practices (continuous application of acid forming fertilizers), removal of organic matter, and contact exchange between exchangeable hydrogen on root surfaces and microbial production of nitric and sulfuric acids can also contribute to soil acidity [2]. Soil acidity is often an insidious soil degradation process, developing slowly; although indicators, such as falling yields, leaf discolorations in susceptible plants, and lack of response to fertilizers might indicate that soil pH is declining to critical levels [3]. Theoretically, soil acidity is quantified based on H+ and Al3+ concentrations of the soils [4]. Acidic soils limit the production potential of crops because of low availability of basic cations and excess of hydrogen (H+) and aluminum (Al3+) in exchangeable forms. It affects beneficial microorganisms, reduced root growth, which limits absorption of nutrients and water [5], consequently, leading to poor plant growth and yield of crops. However, Al3+ toxicity is one of the major limiting factors for crop production on acid soils by inhibiting root cell division and elongation, thereby, reducing water and nutrient uptake [6] poor nodulation or mycorrhizal infections.

Acidic soil is mostly distributed in developing countries, where there is high population growth, and food demand is ever increasing. Acid soils make up approximately 30% of the world’s total land area and more than 50% of the world’s potentially arable lands, particularly in the tropics and subtropics [7]. Acidic soils cover a total of 1.66 billion hectares in developing countries, while the total area affected by soil acidity is about 4 billion hectares [8]. In high rainfall areas, excessive rainfall coupled with unfavorable temperature and precipitation is high enough to leach appreciable amounts of exchangeable basic cations [9].

Soybean production and productivity have been growing rapidly in Ethiopia, in the past decade. According to the Agricultural Sample Survey of CSA (Central Statics Agency) [10], 130,022.00 private peasant holdings cultivated about 36,635.79 hectares of land and produced about 812, 34.659 tons of soybean. The average production of soybean in the country is, therefore, 2.2 t ha-1 while, that of the Mettu area is by far below (1.3 t ha-1) the national average due to soil acidity [11].

Lime and fertilizer management practices are of primary importance for the proper management of soil acidity. Application of lime significantly increased root and shoot yields of soybean in Nigeria [12]. Nevertheless, for economic reasons, it is often not practicable for resource-poor farmers to apply high rates of lime [13]. And [14] also reported that application of lime with high rate is not practicable for resource-poor farmers, as well as, mineral fertilizers. However, previous studies revealed the existence of sufficient genotypic variability of bean germplasm for acid-tolerant [15, 16]. Hence, identification of tolerance soybean genotypes to soil acidity is an economically feasible option that might serve as an acid soil management practice [11]. Hence, the identification and use of soybean genotypes that are tolerant to acid soil conditions of Southwestern Ethiopia is a very useful approach to ensure economic stability to many subsistence farmers, who cannot afford the application of liming materials practices [11]. A preliminary field screening of soybean genotypes in southwestern Ethiopia has demonstrated the presence of genetic variability among genotypes in tolerating soil acidity stress. Studying responses of selected genotypes with contrasting tolerance to soil acidity may help in generating information that could be utilized by breeding programs aimed at developing aluminum-tolerant cultivars for areas where soil acidity remains a key environmental constraint to crop production. Therefore, to meet the demand of soybean in Ethiopia including the study area, emphasis should be given to increase the productivity of the crops through the use of genotypes that can tolerate acid stressed soil conditions. The objective of this study was to test the hypothesis that differences exist in growth, root, yield and yield parameters among soybean genotypes selected for soil acidity tolerance when subjected to limed and unlimed acid soil.

Materials and methods

Description of the study site

The field experiment was conducted at Mettu Agricultural Research Sub Center. Mettu is located in south western Ethiopia at 8°19’ 0" N latitude, 35°35’ 0"E longitude, and at the altitude of 1550 meters above sea level. The average annual rainfall of the study site was 1835 mm/annum, an annual mean minimum and maximum temperatures were 12 and 27 0C respectively (Figs 1 and 2).

Fig 1

Mean minimum and maximum temperatures (°C) of Mettu during crop growth period in 2017.

Fig 2

Monthly total rainfall (mm) of Mettu during crop growth period in 2017.

The soil of the study area has a pH (H2O) value of 4.5, exchangeable acidity of 2.82 cmol kg-1 soil and soil available phosphorus level of 1.16 ppm before applying the treatments. Physical and some chemical properties of the soil in the study area before sowing and after harvesting are presented (Table1).

Table 1

Physicochemical properties of the experimental soil prior to sowing and after harvesting.

Parameters	Before sowing	after harvesting
Particle size distribution		Limed	Unlimed
Clay (%)	49.00
Sand (%)	38.00
Silt (%)	13.00
Textural class	Clayey
pH (H2O)	4.400	4.73	4.48
Exchangeable acidity (cmol(+)/kg)	2.720	1.52	2.41
Exchangeable Al (cmol(+)/kg)	1.460	0.93	1.38
Organic carbon (%)	2.210	2.45	2.22
CEC (cmol (+) kg-1)	18.75	21.04	18.89
Total N (%)	0.210	0.24	0.22
Available P(BrayII) (mg kg-1)	2.950	4.39	2.98
Exchangeable K (cmol (+) kg-1)	0.330	0.67	0.40
Exchangeable Ca (cmol(+) kg-1)	3.550	5.39	3.81
Exchangeable Mg (cmol(+) kg-1)	1.380	1.59	1.40

Soil Sampling and analysis

Prior to the field experimentation both undisturbed and disturbed samples were collected. Three undisturbed soil samples were taken by core sampler. Fresh weight and an oven dry weight at 105°C, of the soil samples was used to determine bulk density [17]. Five random disturbed soil samples (0-15cm depth) were collected diagonally and composite soil sample was made.

The composite sample was used for soil physiochemical analysis, and for the determination of lime requirement of the soil. The disturbed soil samples were air dried and sieved to pass through 2 mm sieve, and placed in a labeled plastic bag. Then, the samples were transported to Jimma Agricultural soil and plant tissue analysis laboratory. The soil sample were analyzed for particle size distribution(soil texture), which was done by Bouyoucos hydrometer method as [18]; while soil exchangeable acidity, exchangeable bases, soil pH, organic carbon(OC), total nitrogen(TN), available phosphorus and cation exchange capacity (CEC) for soil chemical analysis were selected. Available soil P and exchangeable acidity were determined using Bray-II method, as described by [19, 20] respectively.

After harvesting soil sample were taken from lime treated and untreated separately. The collected samples were air dried and sieved to pass through 2 mm sieve and submitted to soil laboratory for soil chemical properties analysis. Organic matter was determined using wet oxidation; Total N was determined by Kjeldahl method, as described by [21]. Cation exchange capacity (CEC) and exchangeable bases (Ca, Mg, K and Na) were determined ammonium acetate at pH 7. The potential cation exchange capacity (CEC) of the soil was determined from the NH4+ saturated samples that were subsequently replaced by K+ using KCl solution. The excess salt was removed by washing with ethanol and the NH4+ that was displaced by K+ was measured using the micro-Kjeldahl procedure [22], and reported as CEC. Exchangeable Ca and Mg was analyzed using Atomic Absorption spectrophotometer (AAS). Exchangeable Na and K were analyzed using flame photometer as described by [22].

Available soil P was determined using Bray-II method, as described by Bray and Kurtz (1945). The soil pH was determined in soil water suspension of 1:2.5 (soil: water ratio) using pH meter, as described by Van Reeuwijk (1992) [23]. Exchangeable acidity was determined by saturating the soil samples with potassium chloride solution and titrates with sodium hydroxide as described by [13]. From the same extractant, exchangeable Al in the soil was titrated with a standard solution of 0.02M HCl.

Determination of lime requirements

The amount of lime applied was determined based on the exchangeable acidity, mass per 0.15m furrow slice and bulk density of the soil) [24], considering the amount of lime needed to neutralize the acid content (Al + H) of the soil up to the permissible acid saturation level for soybean growth.

Where: BD = bulk density, EA = exchangeable acidity (exch. H+ + Al3+), LR = lime requirement, 0.15m = plough depth/depth of lime incorporation.

Planting material, treatments, experimental design and procedures

The treatments comprised of two factors namely; two soil amendments (control or no lime and limed) and fifteen different soybean genotypes (Table 2). The treatments were laid out in split plot design. The experiment has three technical replications and six biological replication in 4m by 2.4 m (9.6 m2) plot size. Per row eighty (80) and per plot/treatments 320 seeds were used. Soil amendments (lime and unlimed) applied as main plot treatments and soybean genotypes were applied to sub plot treatments. The different soybean genotypes for the trial were identified from previous advanced Multi-Location Yield Trials, including previous soil acidity tolerance screening trials.

Table 2

Soybean genotypes used for the experiment.

Genotypes	Back ground information and Source
JM-CLK/CRFD-15-SA	Inbreed line identified from local crosses at JARC
JM-ALM/PR142-15-SC	Inbreed line identified from local crosses at JARC
JM-ALM/H3-15-SC-1	Inbreed line identified from local crosses at JARC
BRS 268	Introduced from Brazil
JM-HAR/DAV-15-SA	Inbreed line identified from local crosses at JARC
JM-CLK/G99-15-SC	Inbreed line identified from local crosses at JARC
JM-CLK/G99-15-SB	Inbreed line identified from local crosses at JARC
JM-H3/SCS-15-SG	Inbreed line identified from local crosses at JARC
Pl 567046A	Introduced from USA
SCS-1	Pipe line from Pawe agricultural research Center
Pl 423958	Introduced from USA
H-7	Pipe line from Mozambique ARI
HAWASSA-04	Released variety from Hawassa Agricultural research

JARC = Jimma Agricultural Research Center

The lime requirement (LR) of the soil for the plots was determined based on exchangeable acidity (EA) or acid saturation of the experimental soil. The lime rate was, therefore, 3457.8 kg/ha based on exchangeable acidity of the soil. Calcium carbonate (CaCO3) was used as the source of lime and the whole doses of lime were broadcasted on limed plots manually, uniformly and mixed in the top 15 cm soil layer, a month before sowing. Reduction percentage for grain yield, root volume, growth and nodulation parameter was calculated as the ratio in lime treated to lime untreated soil, which also showed higher differences among the tested genotypes. The seeds were sown in rows to maintain plant to plant distance of 5 cm and 60 cm between rows. The cropping was done in main season by rain fall without any germination and seedling establishment problem. Cultural practices (i.e. weeding, hoeing etc, the experimental field was weeded by hand five times during the growing period uniformly for all treatments).

Statistical analysis

The data was subjected to analysis of variance (ANOVA) using Statistical Analysis System (SAS) software version 9.3 [25] using proc GLM procedure. The difference between treatment means was separated using LSD 5% value. Correlation analysis between the traits was carried out to determine the magnitude and degree of their associations.

Results and discussion

Effects of soil acidity on yield and yield components of soybean genotypes

Genotypes reflected significant differences for number pods per plant, number of seeds per plant, grain yield, and hundred seed weight and above ground biomass in both limed and unlimed soil regimes (Table 3). The interaction of amendment*genotypes was also highly significant (p≤0.01) for all yield components and yield, however hundred seed weight was only affected by the main effect of genotypes and amendments.

Table 3

Mean square of growth, root, nodulation, yield and yield components of soybean genotypes grown on limed and unlimed soil on field.

Source of variations	Gen	Lime	Lime*Gen	Error (a)	Total
Parameters
Yield	582515.8**	341225.8**	98147.32**	4211.35	10148754.36
No of pod per plant	195.62**	239.44**	39.59**	0.41346	3558.5
No of seed per plant	855.29**	801.62**	144.54**	3.444	15005.62
Above ground biomass	5.275**	5.436**	1.3597**	0.1852	109.9
Number of nodule	206.31**	1626.47**	55.06**	1.143	5350.77
Root dry weight	0.093**	0.2722**	0.01715**	0.001716	1.9161
Plant height	810.97**	577.85****	7.4215**	2.143	12190.7
Root volume	1.0074**	4.71512**	0.2408ns	0.227	35.624
Shoot dry weight	7.3028**	40.1735**	2.141**	0.0228	173.756
Hundred seed weight	19.486**	10.64**	0.739ns	3.122	492.733

** = highly significant different at 1% level of significance, ns = non-significant d/t at 5% level of significance, Gen = genotypes

The response of the observed soybean characters in acidic soil varied among genotypes. Grain yield, number of pods per plant, number of seeds per plant, hundred seed weight and above ground biomass in unlimed soil with low pH was lower than in treated soil or same with that in limed (Table 4). Even, grain yield of BRS268 genotype under unlimed acid soil were higher than in limed acid soil.

Table 4

Interaction effect of genotypes and lime for yield and yield components of soybean genotypes grown under limed and unlimed soil at Mettu during 2017 main cropping season.

Genotypes	Yield (kg/ha)		NPPP		NSPP		AGB (ton/ha)
	L	UL	L	UL	L	UL	L	UL
PI567046A	1943.93a	1069.87d-i	47.1a	26.6cd	92.33a	55.87c	7.02a	3.23e-k
HAWASSA-04	1576.77ab	1553.11bc	29.36bc	22.93gh	60.73b	41.53e-i	5.06b	4.2bc
JM-PR142/H3-15-SB	1328.29b-d	1027.24e-j	21.53h-k	19.46l-n	43.67ef	37.13j-l	4.24bc	3.58c-g
BRS268	1143.47d-g	1319.83b-e	30.33b	27.6cd	47.73d	47.73d	4.01cd	3.79c-f
JMALM/PR142-15-SC	1214.46c-f	1121.35d-g	20.27k-m	21.33i-k	44.9de	44.67de	4.01c-e	3.96c-e
JM-H3/SCS-15-SG	956.49f-k	1096.45d-h	20.53j-l	20.46j-m	44.36de	43.53ef	3.52c-h	3.57c-g
JM-CLK/G99-15-SB	1076.24d-h	756.98j-p	22.93gh	21.8h-j	38.9i-k	39.13h-j	2.79h-m	2.65j-n
JM-CLK/CRFD-15-SA	935.05f-l	643.49m-p	22.53hi	18.07m-o	40.33f-j	33.47l-n	3.43d-j	2.89g-m
JM-DAV/PR142-15-SA	934.71f-l	915.36g-m	24.33fg	24.8ef	42.76e-h	42.26e-i	2.99g-m	3.07f-l
H-7	772.48j-p	821.79h-n	21.33i-k	18nop	39.67g-j	36.87j-l	2.44l-n	2.27m-o
JM-CLK/G99-15-SC	783.83i-o	818.21h-n	22.53hi	21.93h-j	43.13e-g	43.07e-g	3.51c-i	3.52c-h
SCS-1	618.95n-p	510.49p	17.93n-p	16.53p	32.16mn	29.8n	2.58k-n	2.36l-n
JM-HAR/DAV-15-SA	737.46k-p	690.96k-p	19.27l-n	17.4op	34.33lm	31.87mn	2.35l-n	2.23m-o
JM-ALM/H3-15-SC-1	653.17m-p	637.54n-p	21.27i-k	18.93m-o	39.1ijk	35.27k-m	3.06f-l	2.73h-m
PI423958	682.82l-p	528.21o	13.33q	9.76r	22.13o	14.33p	1.87no	1.43o
Mean	1023.87	900.73	23.63	20.37	44.40	38.43	3.52	3.04
CV	6.74		2.922		4.48		13.12

Means with the same letters are not significantly different at 5% level of significance. UL- unlimed; L- Limed; NPPP- Number of pod per plant; NSPP–Number of seed per plant; AGB- above ground biomass; CV- coefficient of variation

On average, the genotypes gave higher yield and yield components in lime treated soil (Table 4). PI567046A genotype gave higher grain yield, above ground biomass, number of pods and seeds per plant in lime treated acid soil; while genotype SCS-1 gave the lowest yield and genotype PI423958 gave the lowest number of pods, seeds and above ground biomass in lime untreated acid soil (Table 4). Under lime untreated soil condition, the maximum grain yield and above ground biomass was obtained from variety HAWASSA-04, and genotypes BRS268 and PI567046A gave highest number of pods and seeds per plant respectively. Under unlimed acid soil condition, the highest increasing percentage for yield and above ground biomass, was shown by BRS268 and JM-DAV/PR142-15-SA respectively, while the highest decreasing percentage was shown by PI567046A for both yield and above ground biomass.

The yield increments with lime application might be due to the probability of obtaining the available P from decomposed OM by microorganisms, when the pH value of the soil improved due to liming, which might have resulted in increased grain yield. Liming also improved the ability of the plant to absorb P, when Al toxicity has been eliminated, and enhanced the vegetative growth of soybean genotypes, which resulted in increased dry biomass yield. In line with this result, [26] also reported that the highest barley grain yield was obtained under the application of 2.2 t/ha lime than unlimed acid soil. The genotypes responded to the applied lime for number of pod and seed, which might be due to lime enhanced vegetative growth and make genotypes to bear higher number of pod than lime untreated acid soil and also lime is neutralized acid soil which might increase the availability of phosphorus for plant uptake by reducing phosphorus fixation on acid soil. Lime also improved soil pH and enhanced growth and yield of soybean genotypes, as a result of increased P availability, photosynthesis intensity, flowering, seed formation and fruiting of the crops also increased (Kisinyo et al., 2016) [33]. In line with this results [13] reported that lime application increased a number of pod and seed per plant. [27] also reported that the application of lime produced the highest seeds per plant than unlimed soil. [28] reported 36.4% plant height decrease in soybean on unlimed acid soil compared with limed acid soil which has a direct relationship with yield increment under limed soil conditions.

The highest hundred seed weight was recorded for PI423958 genotype under lime treated soils and the lowest hundred seed weight was recorded for H-7 under lime untreated soil (Tables 5 and 6). In this study, the variable of tested genotypes has been observed, which indicates the presence of difference among the tested genotypes for hundred seed weight. Application of lime didn’t affect hundred seed weight of genotypes (Table 5). In agreement with this result, [29] reported significant difference among soybean genotypes for hundred seed weight, in which the highest hundred seed weight was produced by BFS 39 genotype and the lowest hundred seed weight was recorded from Roba. [30] reported non- significant effect of liming on hundred seed weight of common bean. In general; lime application to the soil increased yield, number of pod and seed and above ground biomass of soybean genotypes by about 13.67, 16.06, 15.53 and 16.18% respectively, however hundred seed weight were not affected by lime.

Table 5

Average values of grain yield (kg/ha), NPPP, NSPP, AGB (ton/ha) and HSW (g) of soybean genotypes grown under limed and unlimed acid soil at Mettu during 2017.

Treatments	Yield (kg/ha)	NPPP	NSPP	AGB(ton/ha)	HSW(g)
Limed	1023.87a	23.63a	44.40a	3.525a	13.34a
Unlimed	900.73b	20.36b	38.43b	3.033b	14.34a
PR	13.67	16.06	15.53	16.22	-6.97

Means with the same letters are not significantly different at 5% level of significance. NPPP- Number of pod per plant; HSW = hundred seed weight, NSPP–Number of seed per plant; AGB- above ground biomass, PR = percent of reduction

Table 6

Main effect of soybean genotypes for hundred seed weight grown under acid soil at Mettu on field during 2017 main cropping season.

Sub-plot treatments (Genotype)	HSW (g)
PI423958	17.5a
JMALM/PR142-15-SC	16.43ab
HAWASSA-04	15.08bc
JM-H3/SCS-15-SG	15.078bc
JM-PR142/H3-15-SB	14.68bc
BRS268	14.46bc
JM-CLK/CRFD-15-SA	14.228c
JM-HAR/DAV-15-SA	13.83c
JM-CLK/G99-15-SB	13.66c
JM-CLK/G99-15-SC	13.39c
JM-ALM/H3-15-SC-1	13.35c
SCS-1	13.31c
JM-DAV/PR142-15-SA	13.18c
PI567046A	11.08d
H-7	10.53d
CV	12.617

Means with the same letters are not significantly different at 5% level of significance. HSW = hundred seed weight, CV = Coefficient of variation

Hundred seed weight is higher in un-limed soil, this might due to the improvement of soil pH in response to lime amendment, which enhanced growth and yield of the plant, as a result of increased availability of P that might have increased intensity of photosynthesis, flowering, seed formation and fruiting, as a result these formed fruit is competed for nutrient to fulfill the seed and the seed size become decreased which have the direct effect on seed weight.

Effect of soil acidity on root, growth, nodulation parameter of soybean genotypes

There were highly significant (P<0.01) differences among genotypes for root dry weight, number of nodule, plant height and shoot dry weight in both soils regimes. The interaction of lim ing*genotypes was also highly significant(p≤0.01) for root dry weight, number of nodule, plant height and shoot dry weight, except for root volume only the main effect of liming and genotype s were significant. Growth, root and nodulation parameters of soybean genotypes grown under lime treated and untreated soils are indicated in (Tables 7 and 8). On average, the genotypes gave higher root, growth and nodulation parameters under lime treated acid soil (Tables 7 & 8). These results signified that application of lime increasing root, growth and nodulation parameters. JMALM/PR142-15-SC and BRS268 genotype gave higher root volume and root dry weight in both limes treated and untreated soil, and indicating these genotypes might be among acidic soil tolerant genotypes; while genotype PI423958 gave the lowest root dry weigh on lime untreated acid soil (Table 8). [31] reported that among the fifteen soybean genotypes tested MLGG 0064 genotype showed the highest root dry weight under the control soil condition (pH 7), while the lowest root length was shown by genotype MLGG 0377 in Mn toxicity condition, which shows varietal difference for acid soil adaptation.

Table 7

Interaction effect of genotypes and lime for SDW, NN and PHT of soybean genotypes grown under limed and unlimed soil at Mettu during 2017 main cropping season.

Genotypes	SDW (g/plant)		NN/plant		PHT (cm)
	L	UL	L	UL	L	UL
PI567046A	6.32cd	6.32cd	32.56f	20m	83.73a	73.267b
HAWASSA-04	7.045ab	7.045ab	39.067b	33.6e	55.40c	50.33cdef
JM-PR142/H3-15-SB	5.40hij	3.99no	39.40b	32.27fg	54.72cd	47.00efghi
BRS268	5.93defg	5.95def	31.23ghi	31.26ghi	53.80cde	48defgh
JMALM/PR142-15-SC	6.16cde	5.45ghij	37.33c	30.87hi	46.27fghi	44.2fghijk
JM-H3/SCS-15-SG	5.58fghi	4.46lmn	35.20d	26.2j	48.93cdefg	44.87fghij
JM-CLK/G99-15-SB	7.56a	4.46lmn	37.33c	23.33kl	43.067ghijk	40.67jklm
JM-CLK/CRFD-15-SA	4.34mn	2.92pq	37.13c	22.67l	48.93cdefg	42.73ghijk
JM-DAV/PR142-15-SA	4.76klm	4.78klm	32.40f	31.67fg	37.33klmno	34.40lmno
H-7	5.18ijk	4.027no	39.00b	34.13de	32.00nop	29.60op
JM-CLK/G99-15-SC	5.73efgh	4.80klm	30.33i	23.2kl	48.8cdefg	43.13ghijk
SCS-1	3.60o	1.97r	24.20k	15.67o	44.83fghij	39.0jklmn
JM-HAR/DAV-15-SA	4.83kl	4.97jk	31.23ghi	30.8hi	38.6jklmn	33.60mnop
JM-ALM/H3-15-SC-1	2.94p	2.38qr	34.36de	17.6n	45.87fghi	41.50hijkl
PI423958	6.48bc	3.69o	55.27a	35.16d	32.39nop	26.20p
	5.45	4.12	35.72	27.22	47.63	42.56
CV	3.15		3.39		3.245

Means with the same letters are not significantly different at 5% level of significance. UL- unlimed; L- Limed; SDW- shoot dry weight; NN–number of nodule; PHT- plant height; CV- coefficient of variation

Table 8

Main effect of soybean genotypes for RV and interaction effect of lime and genotypes for RDW grown under limed and unlimed acid soils at Mettu on field during 2017 main cropping season.

Genotypes	RDW (g/plant)		V/plant in ml
	Limed	Unlimed
PI567046A	0.75cde	0.433j	2bcde
HAWASSA-04	0.81a-d	0.807abcd	2.33bc
JM-PR142/H3-15-SB	0.79bcd	0.74cde	2.5b
BRS268	0.84a-d	0.83abcd	2.33bc
JMALM/PR142-15-SC	0.937a	0.873abc	3.17a
JM-H3/SCS-15-SG	0.71d-g	0.637efgh	2.167bc
JM-CLK/G99-15-SB	0.647efgh	0.44j	1.5e
JM-CLK/CRFD-15-SA	0.893ab	0.75cde	2.43b
JM-DAV/PR142-15-SA	0.73def	0.72def	1.87cde
H-7	0.637efgh	0.58ghi	1.833cde
JM-CLK/G99-15-SC	0.657efgh	0.47ij	1.6de
SCS-1	0.8abcd	0.47ij	2.1bcd
JM-HAR/DAV-15-SA	0.55hij	0.55hij	2bcde
JM-ALM/H3-15-SC-1	0.717defg	0.657efgh	2.033b-e
PI423958	0.59fghi	0.427j	1.833cde
Mean	0.735	0.625	CV = 22.55
CV	6.093

Means with the same letters are not significantly different at 5% level of significance. RDW- root dry weight; RV–root volume; CV- coefficient of variation

The alteration of root dry weight and root volume includes decreasing and increasing of the root length and root hair. Decrease percentage of root dry weight and root volume in acid soil stress conditions varied among the tested genotypes. Limed soil condition showed the highest root dry weight and root volume than in unlimed soil. This might be due to liming improved the P uptake capacity of plants which facilitate root growth, and then increased root diameter or root thickness of the genotypes, and root dry weight is the result of root growth and development, including root length and number of lateral roots. Alteration in root length and number of roots causes an alteration in root dry weight and root volume. Alteration also occurs on root hair length and root hair density [32] that cause an alteration in root dry weight.

There was no negative values existed for root dry weight in unlimed acid soil conditions (Table 10), but negative value existed for number of nodule. Negative value suggests an increasing variable from the optimal or relatively optimal condition to the severer condition. The highest number of nodule was obtained from JM-DAV/PR142-15-SA; while the lowest number of nodule was recorded from SCS1 genotype. This might be due to liming effect on nodule weight and nodule numbers. There was one genotype showing an increase in number of nodules in unlimed ed acid soil condition. In line with this finding [11] reported two soybean genotypes i.e., H3 and PR-142 [15] showed the highest number of nodules per plant at 100 kg ha-1P with lime and Essex-1 genotype showed the lowest number of nodules per plant at lime untreated plot among the other tested genotypes. The highest plant height was recorded for PI567046A genotype both under lime treated and untreated acid soils. On the other hand, the shortest plant height was recorded for PI423958genotype under lime untreated soil. This indicated that genotypes responded to liming, which might be due to the effect of liming that neutralized soil acidity, which in turn might have improved the availability of plant nutrients, particularly phosphorus and calcium and lowered the concentration of toxic cations, mainly Al3+ ions. The results are similar with the results of [33] who reported that a growth of plant is increased on acid soil in response to the application of lime.

Table 10

Decrease percentage of yield, above ground biomass, number of pod and seed per plant, number of nodules, root dry weight and plant height of some soybean genotypes under unlimed acid soil conditions compared with limed acid soil.

Genotypes	YLD	AGB	NN	PHT	RDW	NPPP	NSPP
HAWASSA-04	1.50	17.0	13.9	9.13	0.00	21.6	31.6
PI567046A	44.96	54.0	38.4	12.51	42.7	43.4	39.5
PI423958	22.64	23.4	36.5	18.8	27.1	27.4	35.26
JMALM/PR142-15-SC	7.67	1.25	17.3	4.39	7.40	-5.2	0.52
JM-HAR/DAV-15-SA	6.31	5.11	1.39	12.95	0.00	9.69	7.18
JM-PR142/H3-15-SB	22.67	15.5	18.1	14.1	6.30	9.63	14.96
H-7	-6.38	6.84	12.4	7.5	7.90	15.6	7.06
BRS268	-15.4	5.41	-0.1	10.78	1.20	9.03	0.00
JM-H3/SCS-15-SG	-14.6	-1.3	25.5	8.32	11.3	0.36	1.66
JM-CLK/CRFD-15-SA	31.18	15.7	38.9	12.67	15.7	19.8	17.02
JM-ALM/H3-15-SC-1	2.40	10.7	48.6	9.43	8.50	10.9	9.72
JM-CLK/G99-15-SC	-4.39	-0.3	23.5	11.61	27.7	2.66	0.15
SCS-1	17.53	8.41	35.2	13.02	46.3	7.81	7.07
JM-CLK/G99-15-SB	29.66	4.91	37.5	5.52	31.3	4.97	-0.51
JM-DAV/PR142-15-SA	2.06	-2.5	2.26	7.87	2.70	-1.9	1.17

Where, NPPP = number pod per plant, NSPP = number of seeds per plant, PHT = plant height, RDW = root dry weight, YLD = yield, NN = number of nodules per plant, AGB = above ground biomass

The highest shoot dry weight was obtained from JM-CLK/G99-15-SB genotype, while the lowest shoot dry weight were recorded from SCS-1 genotype (Table 7). The reduction of shoot dry weight under the control or unlimed acidic soil condition might be due to Al toxicity, and low Ca, Mg and P concentrations in the shoot, which resulted in decreased photosynthetic capacity that directly affected, shoot growth and developments. This alteration was also due to the low pH inhibits root growth; reduce Ca2+and Mg2+ in the leaf and reduce rhizobia activity to f orm nodule [34] as well as the Mn toxicity. Different result was reported; [35] reported that decreasing solution pH and Ca concentration decreased the shoot dry weight. However, plant height, root volume, root dry weight, number of nodule and shoot dry weight is also affected by the genotypes. Lime applications to acid soil increased plant height, root volume, root dry weight, number of nodule and shoot dry weight of soybean genotypes by about 11.91, 24.47, 17.6, 31.22 and 32.5% respectively (Tables 9 and 10).

Table 9

Average values of SDW (g/plant), NN/plant, PHT, RDW (g/plant) and RV (g/plant) of soybean genotypes grown under limed and unlimed acid soil at Mettu.

Treatments	SDW (g/plant)	NN/plant	PHT (cm)	RDW (g/plant)	RV /plant
Limed	5.46a	35.72a	47.64a	0.735a	2.34a
Unlimed	4.12b	27.22b	42.57b	0.625b	1.88b
PR	32.52	31.23	11.91	17.6	24.46

Means with the same letters are not significantly different at 5% level of significance. RDW- root dry weight; RV- root volume, SDW-shoot dry weight, PHT-plant height, NN-number nodule; PR = percent of reduction; CV- coefficient of variation

Correlation analysis

Grain yield was significantly (P≤ 0.01) and positively correlated with all root parameters viz., root dry weight and root volume and with all growth parameters viz., plant height and shoot dry weight and also with number of nodule at both limed and unlimed soil (Table 11). The significant and positive correlations of grain yield with the rooting parameters viz., root volume and root dry, under acid soil condition or under unlimed acid soil (hydrogen and aluminum toxicity) indicates the importance of the root parameters for acid soil tolerance. This also implies that selection for acid soil tolerance should consider these important root parameters. Similar to this finding [11] also reported the significant and positive associations of soybean grain yield with its root characters like root volume, root dry and fresh weight.

Table 11

Pearson correlation analysis for growth, root, nodulation, yield and yield components of soybean genotypes grown under lime treated (1st) and lime untreated (2nd) soil on field at Mettu.

	YLD	PHT	NSPP	NPPP	AGB	SDW	RV	RDW	NN
YLD	1
PHT	0.82**	1
NSPP	0.87**	0.90**	1
NPPP	0.82**	0.87**	0.95**	1
AGB	0.90**	0.91**	0.92**	0.86**	1
SDW	0.56**	0.21ns	0.31*	0.28ns	0.31*	1
RV	0.15ns	0.15ns	0.04ns	-0.07ns	0.22ns	-0.08ns	1
RDW	0.37*	0.38*	0.27ns	0.23ns	0.43**	-0.07ns	0.55**	1
NN	0.01ns	-0.29ns	-0.25ns	-0.29ns	-0.19ns	0.43**	0.07ns	-0.18ns	1
	YLD	PHT	NSPP	NPPP	AGB	SDW	RV	RDW	NN
YLD	1
PHT	0.52**	1
NSPP	0.66**	0.75**	1
NPPP	0.68**	0.67**	0.92**	1
AGB	0.76**	0.55**	0.70**	0.67**	1
SDW	0.63**	-0.13ns	0.24ns	0.35*	0.45**	1
RV	0.48**	0.19ns	0.21ns	0.23ns	0.51**	0.34*	1
RDW	0.59**	0.09ns	0.29ns	0.36*	0.61**	0.51**	1.0**	1
NN	0.39**	-0.36*	-0.15ns	-0.08ns	0.07ns	0.70**	0.27ns	-0.18ns	1

Where, NPPP = number pod per plant, NSPP = number of seeds per plant, PHT = plant, Height, SDW = shoot dry weight, RDW = root dry weight, YLD = yield, NN = number of nodules per plant, AGB = above ground biomass

Grain yield is the product of its yield components, such as number of pods per plant, number of seeds per plant and above ground dry biomass were highly significant and positively correlated with its grain yield at both lime treated and untreated acid soil (Table 11). However, grain yield was strongly correlated with above ground biomass (r = 0.90), followed by number of seeds (r = 0.87) and number of pods per plant (r = 0.82) at limed soil among yield parameters, respectively. Other authors, such as [36, 37] reported that the significant associations of barley grain yield with its yield components. Results obtained in this study on soil treated with lime clearly showed that the remarkable increase in number of pods and seeds per plant, and greatly contributed to increase in grain yield of soybean. The negative correlation of number of nodules with number of seed and pod under unlimed soil (Table 11) indicates the competitiveness of these traits.

Conclusion

For the conclusion, the observed characters showed a different response in acid soil toxicity. The fifteen genotypes responded differently to acid soil. A preliminary field screening of soybean genotypes in south western Ethiopia has demonstrated the presence of genetic variability among genotypes in tolerating soil acidity stress. The observed characters of the sensitive genotypes decreased, while the tolerant genotypes could remain stable or increased. Root dry weight, root volume, number of nodule, plant height, shoot dry weight, grain yield, biomass, number of pod per plant, number of seed per plant, and hundred seed weight under unlimed soil were lower than in limed soil condition. However, not all these characters always decrease in unlimed soil condition. Their increments of grain yield in unlimed soil were found for BRS268 genotype. Genotype of BRS268 was the tolerant genotypes based on the reduction percentage of selected parameters. These results also give a clear indication that the grain yield was very closely associated with number of pods per plant, seed per plant, root dry weight, root volume, and shoot dry weight and number of nodule in both unlimed and limed soil. It seems that these parameters are useful characters to select for high yield in soybean breeding programs for soil acidity tolerance. Studying responses of selected genotypes with contrasting tolerance to soil acidity may help in generating information that could be utilized by breeding programs aimed at developing aluminum-tolerant cultivars for areas where soil acidity remains a key environmental constraint to crop production. In conclusion identification and use of soybean genotypes that are tolerant to acid soil conditions of Southwestern Ethiopia is a very useful approach to ensure economic stability to many subsistence farmers, who cannot afford the application of liming materials practices.

Supporting information" files” raw data for each parameter.

(DOC)

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24 Mar 2021

PONE-D-20-38977

Tolerance to soil acidity of soybean (Glycine max L.) genotypes under field conditions at Southwestern Ethiopia

PLOS ONE

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Reviewer #2: Yes

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Reviewer #1: Broad Comments

It would be very helpful if the authors would include continuous line numbers to facilitate the review process. Due to a lack of line numbers, the authors should please refer to the highlights in the pdf in order to see the reviewer comments for each specific section of the manuscript.

One issue is that it is unclear how many biological replicates were used in the experiments done. The authors need to have done at least three biological replicates and three technical replicates for each assay. From the descriptions of the experiments, it is not clear at all what was done. If they only did three technical replicates, then all they measured was the accuracy of the techniques/assays used, not the accuracy of the biological phenomenon. Three biological replicates ensures that the biological effect seen is consistent within individuals of the species tested. They need to clearly describe what is considered as a single biological replicate and what is considered to be a technical replicate. For each table and figure caption/legend, they need to clearly state the number of biological and technical replicates used. This is extremely critical as the authors are doing experiments over multiple soybean genotypes.

For some of the experiments, the authors use 5 random plants of each genotype. This is an extremely limited amount of sampling given that they are drawing conclusions that apply to the genotype. This is even more problematic as the authors do not seem to have biological or technical replicates for the parameters that they tested for each genotype. This needs to be rectified in order to give confidence that the conclusions they provide can be applied to all the individuals within a specific genotype.

In several places, the work done has been unfortunately obscured by very poor English language communication. It is highly recommended that the authors seek the help of English language editors in order to improve the quality of the manuscript. The language errors are sometimes extensive and significantly hamper the ability of the reviewer to understand what is being conveyed. The authors need to edit significant portions of the manuscript for clarity. This will allow the significance of the work done to be properly highlighted.

There are also areas where the authors need to provide citations for the statements they make. The authors also need to provide the raw data used in the analyses in supplementary files.

Reviewer #2: The study has investigated the tolerance to soil acidity of soybean (Glycine max L.) genotypes under field conditions at Southwestern Ethiopia. It is believed that this paper will be found interesting to the reader of the journal. The paper has written excellently and necessary data collected and analyzed critically and described well. However, some of the comments mentioned here need consideration before publication.

Comment: The abstract can serve as a stand-alone document, which succinctly described. So, the abstract should cover the salient findings more critically. Some sentences are too long in abstract, methodology and results and discussion. Describe it briefly or split it another sentence if possible.

Comment: On what basis, Genotype BRS268 showed higher yield (1319.83 kg ha-1 ) under lime untreated acid soil than lime treated acid soil(1143.47 kg ha -1 ) and showed less reduction percentage for number of nodule, root weight and number of seeds per plant? Either it resistant? Is it previously identified/claimed?

Comment: The introduction is informative, precise, and comprised of relevant content. The literary structure of the introduction is also good. Citation is missing at the end of paragraph 1, 3, 4, etc.

Comment: In introduction, Line 15-17 and 34-37 are looking repeated.

Comment: Material and methods section looks fine, the used methods are well presented. The experimental design was appropriate and the applied protocols were used correctly. The authors organized very nice research. The methods are simple and sufficiently described. However, gave proper reference that from the soybean genotypes identified previously.

Comment: In Table 3. What does mean Gen? Specify it/mention if used it as abbreviated.

Comment: According to results, the genotype BRS268 gave better yield in un-limed soil when compared to lime treated soil. So therefore it means this variety would not be recommended in lime treated or high pH soil? Justify it. Conclude it in discussion section and conclusion.

Comment: In results you have mentioned and discussed only genotype BRS268 gave better yield in un-limed soil. While there are some other genotypes i.e. H-7 and JM-H3/SCS-15-SG are too exist but not mentioned and discussed?

Comment: Why Average values of hundred seed weight is higher in un-limed soil. Justify it. Gave it reason in discussion section.

Comment: In results, CV is given, however, at some parameters it looks too small and in some it exceeds too large that’s mean standard error (S.E) small or too large, respectively. Why? If possible, either it is better to provide S.E instead of Giving CV?

Comment: Either it will be better to analyze the data statistically separately lime treated and un-limed soil, instead of combine?

Comment: In this paper you have just mentioned and analysed toxicity of H+ and Al3+, Is there no any else toxicity i.e., Fe, Cu, Zn, Mn, etc., as common problem found in acidic soils.

Comment: The discussion section is also well described. Discussion should be appropriate in which results are discussed critically in response to support as well contradiction, instead of describing other cited results. Justify your results with some latest citations.

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Comment: Check references section appropriately according to the journal requirement.

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Reviewer #1: No

Reviewer #2: Yes: Dr. M. Asaad Bashir

Assistant Professor,

Department of Soil Sciences,

Faculty of Agriculture & Environment,

The Islamia University of Bahawalpur, Pakistan.

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Submitted filename: PONE-D-20-38977_reviewer.pdf

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1 Jun 2021

response to reviewer #1, thank you for your contractive comments and suggestion, however please make clear the issues you want to raise, for eg in this manuscript your comment depends on biological replicates which is no more clear for author. thank you

Submitted filename: Response to reviewer 2.docx

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8 Jul 2021

PONE-D-20-38977R1

Tolerance to soil acidity of soybean (Glycine max L.) genotypes under field conditions at Southwestern Ethiopia

PLOS ONE

Dear Dr. Bedassa,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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Reviewer #3: Manuscript has been poorly written and lacks coherence. Line N0.42 rewrite the sentence, sentence is long

Line. No 54 Grammatically incorrect, further the sentence doesn’t give any sence.

Line No 60- 63 rewrite the para.

Line No. 65 (Abush T) delete T.

Line No. 70 replace the word development by identification of .

Line No.71- 73 Sentence is too long and should be modified.

Introduction

It lacks coherence and the language is poor, which can be improved

Materials and methods

Line No. 84 Delete the sentence “According to the weather data obtained from the meteorological station of Mettu Agricultural Research Sub Center”.

Sampling and analysis.

Poorly written

It is not necessary to mention the whole procedure, only mention the method used and reference.

Line No. 125 replace amounts with amount.

Line No. 134 delete was.

Line No. 148 root volume.

Line No 149. Delete the sentence beginning from which-genotypes.

Line No. 151, Not clear, rewrite the sentence.

Results and discussion (sentences have been written long unnecessarily)

Line No. 184Replace the sentence as, Genotypes reflected significant differences for number of pods----------and above ground biomass in both limed and un limed soils.

Line No.190-191. The sentence doesn’t give any sense and should be deleted.

Reviewer #5: Comments

1. The abstract is well written and organized. line 17, “necessary” stage is not correct wording. I suggest to use more suitable word. Separate “BRS268had” into BRS268 had. Furthermore, abstract must be much more quantitative regarding the results and suggested innovation of the study.

2. The literature review needs to be more critical.

3. Please state clearly the novelty of the study and tested hypothesis at the end of the introduction.

4. Line 222: The highest HSW recorded was for PI423958 genotype not JMALM/PR142-15-SC genotype.

5. Table 6 is incomplete. Show HSW for lime and un limed or remove limed from the title if the limed treatments did not show any significant effect on HSW.

6. Provide reference to support the statement within line 235 to 239.

7. Throughout the manuscript, there are several grammatical errors and the English language used are poor or sub-standard.

8. The discussion section should be written well to clearly explain the science behind the results.

9. The paper fails to highlight the significant of the study and the conclusion needs to be expanded significantly to explain clearly about the novelty of the experimental setup. Also, policy recommendations can be suggested.

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2 Aug 2021

one reviewer is making the thing too big than making suggestion

Submitted filename: Response to reviewer 2.docx

Click here for additional data file.

31 Aug 2021

PONE-D-20-38977R2

Tolerance to soil acidity of soybean (Glycine max L.) genotypes under field conditions at Southwestern Ethiopia

PLOS ONE

Dear Dr. Bedassa,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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ACADEMIC EDITOR: Although several opportunities have already been given to authors for improving the manuscript; the presentation of revised manuscript is still poor, and contains many typo and language errors that should have already been addressed by the authors. To avoid repeated rounds of revision it is likely that the manuscript will be rejected if significant improvements are not made in the returned draft.

Authors must revise the language of the draft by a professional English Editor/native speaker prior to submission. 

==============================

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Saddam Hussain

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: (No Response)

Reviewer #5: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #3: Partly

Reviewer #5: (No Response)

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: I Don't Know

Reviewer #5: (No Response)

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #3: Yes

Reviewer #5: (No Response)

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #3: No

Reviewer #5: (No Response)

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #3: Abstract:

Abstract should be concise and precise especially results should be

Introduction:

Justification of the study is well grounded, though there is good scope for its improvement in light of the latest literature

Result and Discussion:

Discussion has been drafted monotonously, there is repetition of few sentences, which are self-explanatory and doesn’t need to be repeated again and again.

In the table genotype SCS-1 is reflecting lower yield under lime application, however genotype PI423958 is showing higher yield in comparison to SCS-1with lower yield attributes, I feel author needs to justify it.

Similarly, BRS268 genotype has reflected higher yield in un-limed soil in comparison to treated soil, which needs justification. Furthermore, yield attributes of the mentioned cultivar are better under treated soil, then how is it possible to yield more under untreated situation.

Line No.19 Insert which, between root volume and Where.

Line No.21 delete “and other’ insert (,)

Line No.22 delete (,) before and

Line No 23 delete “than un limed soils’

Rewrite the para from line No. 21 to Line No. 24, it is grammatically incorrect.

.

Minor corrections to be enacted.

Line No. 41 replace word acid by acidic and replace and by (,) between rainfall and leaching.

Line No. 42 crop management-------soil acidity Line No. 45 rewrite it.

Line No. 51 Delete (also) and (,), further more you are prolonging the sentence unnecessary, which doesn’t give any sense and reduces the quality of writing. So you better rewrite the sentence.

Line No.61 Modify the sentence, there is mention of the name of country twice in the same sentence.

Line No. 67 insert “Of ‘between are and primary.

Line No. 71 replace word tolerance with tolerant.

Line No. 72 identification of tolerant genotypes is not an amendment practice rather it is a management practice. Thus, requires modification.

Line No.87 delete “and’ and replace word “the’ with ‘an’

Line No. 89 is not clear , mention the mean values of both min. and max. temperature clearly.

Line No. 99 insert “of the soil samples was used to determine the bulk density’ after 105oC

Line No. 107 There is no need to write ‘that is among soil physical parameters’ so it should be deleted.

Line No.111

Line No. 134 Delete “was’ in the sentence. The treatments was comprised of two factors namely

Line No. 135 -137. No need to go for repetition of the sentences, I suggest for its deletion.

Line No. 151, Rewrite the sentence.

Minor corrections and typographical err

Line No. 187.Number of seed per plant.

Line No.190 insert, all yield components and yield. And replace were with word ‘was’

Line No. 192.delete toxicity.

Line No. 193 Insert pods and seeds instead of pod and seed per plant.

Line No. 194.word that in limed to be replaced by treated soil.

Line No. 198 word material to be replaced by genotype.

Line No. 204- 206 percentage increase or decrease against treatment is ambiguous and needs clarity.

Line no 223-225 revisit the results, and interpret them clearly as the tables mentioned by author.

Line No. 225 insert “response” after variable.

Line No. 226 doesn’t to be replaced by didn’t.

Line No. 227.Rewrite the Justification given by the author to variable response of genotypes under lime application to 100 seed weight.

Line No. 236 is self-contradictory, elucidate on it.

Line No. 290

Line No. 292 write number of nodules instead of nodule.

Line No. 292-295, rewrite the sentence.

Line No.304-05 check the justification given by Kuswantoro.

Line No. 307. root length and root hair (what is the difference).

Line No.318-320. Justification is not in accordance with the results.

Line No. 320 -325 Justification given by author is entirely different, replace it or come with some clear support.

Line No. 404-405. Give some concreate justification or support.

Table No. 6 under limed and un-limed soils, where are the limed and un-limed columns.

The author has mentioned that the experiment was conducted during 2017/18, where as in the tables he highlights one year data. The author should come clear on it.

Conclusion:

Re write the conclusion, there is no need to elaborate the results in conclusion section. conclusion should be short and precise.

The manuscript needs thorough revision for language editing by a professional native English speaker.

This manuscript also requires a technical review done critically by senior author and remove all the typos present throughout the manuscript.

Reviewer #5: (No Response)

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Reviewer #3: No

Reviewer #5: Yes: Emmanuel Abban-Baidoo

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

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11 Oct 2021

Please both reviewer see carefully what i have incorporated based on your comments in the body of the paper , i have touched all your comments and questions thank you for your time and efforts

Submitted filename: Response to reviewer.docx

Click here for additional data file.

21 Dec 2021

20 Apr 2022

we acknowledge all reviewers for their constructive ideas and comments, however some reviewers are making complex than touching the target problems

Submitted filename: Response to reviewer.doc

Click here for additional data file.

29 Jul 2022

Tolerance to soil acidity of soybean (Glycine max L.) genotypes under field conditions at Southwestern Ethiopia

PONE-D-20-38977R4

Dear Dr. Bedassa,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Saddam Hussain

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

18 Aug 2022

PONE-D-20-38977R4

Tolerance to soil acidity of soybean (Glycine max L.) genotypes under field conditions atSouthwestern Ethiopia

Dear Dr. Bedassa:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Saddam Hussain

Academic Editor

PLOS ONE