Integrated agroforestry systems improve soil carbon storage, water productivity, and economic returns in the marginal land of the semi-arid region.

Environmental crises, land degradation, and frequent crop failure threaten the livelihoods of millions of the populace in the semi-arid agroecosystems. Therefore, different combinations of annual crops with perennial fruit trees were assessed to restore the soil carbon, and enhance farm productivity and profitability in a semi-arid climate. The study hypothesized that the integration of perennial fruit trees with seasonal crops may enhance farm productivity, economic returns, and environmental sustainability. Integration of phalsa (Grewia asiatica) with mung bean (Vigna radiata) - potato (Solanum tuberosum) system recorded the highest system productivity (25.9 Mg/ha) followed by phalsa with cowpea (Vigna unguiculata) -mustard (Brassica juncea) systems (21.2 Mg/ha). However, Karonda (Carissa sp.) with mung bean - potato system recorded maximum net return (3529.1 US$/ha), and water use efficiency (33.0 kg/ha-mm). Concerning the benefit-cost (B:C) ratio, among the agroforestry systems, the karonda + cowpea - mustard system registered a maximum BC ratio (3.85). However, SOC density remained higher (9.10 Mg/ha) under the phalsa + cowpea - mustard and Moringa + mung bean - potato system (9.16 Mg/ha) over other systems. Similarly, phalsa + mung bean - potato system had the highest C sustainability index (27.6), carbon sequestration potential (0.6-0.67 Mg/ha/year), and water use efficiency (33.0 kg/ha-mm). Hence, the study suggested that the integration of short-duration leguminous and oilseeds with fruit trees offer a myriad of benefits and an efficient system for restoring the soil C without compromising the food and livelihood security of the rural populace in semiarid regions.

Introduction

The global population will reach ∼11 billion by 2050 (Adam, 2021), hence achieving food security without hampering environmental quality is a global challenge (Babu et al., 2022a). Climate and soil is the major determinant of agricultural productivity, profitability, and human wellbeing (Babu et al., 2022b, Yadav et al., 2021a). Climate adversities had a negative impact on crop productivity, natural resources, and eventually food security, and environmental health (Đorđević et al., 2018, Das et al., 2022). The semiarid region covers a major land chunk globally. The soils of the semiarid region are degraded by faulty land use management resulting in soil organic carbon (SOC) and fertility losses. The agricultural productivity of a semi-arid climate is severely impacted by climate change and management practices (Coulibaly et al., 2020, Liu and Dai, 2020, Khanal et al., 2021), and unsustainable use of natural resources (Asplund et al., 2014). Hence, there is a need to devise appropriate crop and soil management practices that can potentially feed the world population without compromising environmental quality.

Land-use and production diversification can be a possible strategy to face negative climate change effects (Pejin et al., 2012, Babu et al., 2020) and economic uncertainties (Castro et al., 2015, Singh et al., 2021b). An increase in SOC stocks of cultivated land would increase the efficiency of managed soils and enhance the resilience of agriculture in changing climate while minimizing net greenhouse gasses (GHG) emissions (Paustian et al., 2019, Yadav et al., 2021b, Babu et al., 2022b). Compatible association of trees with seasonal crops is called integrated agroforestry systems (AFSs) (Yadav et al., 2021b), and can have positive effects on agricultural production, soil health, and environmental quality (Babu et al., 2020, Jha et al., 2021). More specifically, AFSs as diversified landscapes improve per unit production and soil quality (Babu et al., 2020, Yadav et al., 2021b).

Appropriate tree-crop interaction can potentially improve the economic status, food, and nutritional security of small and marginal farmers through the combined production of food, feed, fiber, and firewood besides mitigating the climate change impact (Dollinger and Shibu, 2018, Omerkhil et al., 2020). More specifically, agroforestry can mitigate the atmospheric GHGs concentration while supporting local farmers to adapt to climate change (Yadav et al., 2021b), because these systems can store more C than arable systems by enhancing the SOC pool (Lorenz and Lal, 2014, Babu et al., 2020). Perennial fruit trees are known for their tolerance against environmental stresses with their ability to withstand weather aberrations and quick biomass gain under resource-limited situations (Carlsson et al., 2017) over annual crops. Sustainably AFSs improve soil fertility by reducing the adverse effects of climatic change which always remains a threat under fragile agro-ecologies (Azembouh et al., 2021). However, a suitable AFSs depends upon many tree-crop-environment interactions in the use of natural resources, complementarity, or competition.

Many researchers have highlighted the promise of the adoption of AFSs as promising land-use systems because they conserve soil and water, reduce soil losses, and sustain higher production, productivity, and profitability (Awasthi et al., 2010, Kuyah et al., 2019, Yadav et al., 2021b). The integrated agroforestry is a supportive from the economic side because it can generate additional employment, especially during the lean season, by providing resources for auxiliary industries (Yadav et al., 2021b). AFSs comprising of both trees and field crops in alleys between two crops can lead to higher productivity under tropical conditions (Hall et al., 2005, Kuyah et al., 2019), and increased well-being (Thorlakson and Neufeldt 2012). The suitable amalgamation of appropriate tree species and annual field crops improves system resilience by minimizing negative impacts (Yadav et al., 2021a). Further, AFSs can reduce the risk in agriculture, especially under marginal and fragile agro-ecologies. Most of these studies on AFSs focused on soil carbon dynamics (Babu et al., 2020, Yadav et al., 2021b), and environmental outcomes (Brown et al., 2018, Miller et al., 2019). It is environmentally necessary to reduce the carbon footprint and improve the soil quality. But it is always not sure that the technology which is environmentally sound may be economically viable. But none of the studies simultaneously assessed the impact of the different tree-crop-based systems including karonda, moringa, phalsa, guava with oilseeds, pulses and vegetables on-farm productivity, profitability, and carbon sustainability, and resource use efficiency, especially under semi-arid climatic conditions. Therefore, a comprehensive assessment of all these outcomes is the dire need to formulate environmentally friendly and economically robust agricultural planning, especially for semi-arid regions. Hence, it was hypothesized that an appropriate combination of seasonal crops along with perennial trees, may increase food production, profitability, carbon allocation in soil, and resource use efficiencies under rainfed and water deficit agro-ecosystems). To prove this hypothesis different combinations of seasonal crops with perennial fruit trees were evaluated for three years (2015–18) in sandy loam soil of the semi-arid region of India (Delhi) with the distinct aims of (1) to assess the effect of different perennial fruit tree-crops combinations on-farm productivity, profitability, and water use efficiency concerning the fallow-mustard and (2) to assess the impact of perennial fruit tree-crop associations on soil sustainable yield index, carbon sequestration potential, and carbon sustainability index under scare moisture condition.

Materials and methods

Study site

The study site was located at ICAR-Indian Agricultural Research Institute, New Delhi. The experimental site lies between 28.40°N, 77.12°E, and 229 m elevation (Fig. 1). The climate of the experimental site was semi-arid, with a mean annual rainfall of 650 mm, most of which is received from July to September. The mean daily minimum temperature in January was 0–4 °C, the maximum temperature in May-June was 40–46 °C, and relative humidity ranged between 67 and 83% during the experimentation years. Table 1 depicts the soil characteristics of the experimental sites before sowing of the crops. The soil pH was 7.6–7.9 and that of electrical conductivity (EC) was 0.28–0.32 dS per m. The soil was sandy loam in texture with the proportion of sand, silt, and clay as 44% sand, 38%, and 18%, respectively. The bulk density (pb) and infiltration ranged between 1.49 and 1.52 Mg/m3 and 24.1–28.2 cm/hr, respectively. The soil's organic carbon (SOC) content and available N (<250 kg/ha) were poor (0.30–0.34), although the available P and K were medium in status.

Fig 1

Map showing study site in India.

Table 1

Physico-chemical properties of the experimental site.

AFS/Parameters	BD (Mg/m3)	Infiltration (mm/hr)	pH	EC (dS/m)	Available N (kg/ha)	Available phosphorus (kg/ha)	Available potash (kg/ha)
Karonda based AFS	1.51a	26.5ab	7.8a	0.32a	152b	18.5a	295a
Phalsa based AFS	1.49a	26.2ab	7.9a	0.30ab	149b	17.6a	298a
Moringa based AFS	1.50a	28.2a	7.6a	0.28b	170a	16.9b	301a
Guava based AFS	1.52a	24.1b	7.7a	0.28b	155b	17.1ab	299a
Fallow-mustard	1.51a	26.2ab	7.8a	0.29b	1.57b	17.8a	301a

BD: Bulk Density; EC: Electrical Conductivity; AFS: Agroforestry systems; N: nitrogen; Means followed by different letters are significantly different concerning the LSD (least significant difference) values at p = 0.05. Significant differences shown are concerning different systems.

Experimental setup and management

To assess the effect of perennial plants in combination with seasonal crops on the growth of field crops, economic returns, water use efficiency, and SOC dynamics, in a semi-arid region. Annual crops viz., cowpea (Vigna unguiculata) and mung bean (Vigna radiata) rotated with potato (Solanum tuberosum) and mustard (Brassica juncea) for three consecutive years (2015–2018) in system mode for four years old plantation of Phalsa (Grewia asiatica), Karonda (Carissa carandas), Drumstick (Moringa oleifera), Guava (Psidium guajava) and Pomegranate (Punica granatum) (Fig. 2). The trees were planted in a strip of 100 m and that of alleys for annual crops was 100 m × 5 m. The study was conducted in a randomized block design (RBD) with three replications. The pruning of every fruit plant was done during the winter season as per standard protocols to minimize the shedding impact on the seasonal crops.

Fig 2

Integrated tree-crop based production systems, a. Phalsa + mung bean, b. Phalsa + cowpea, c. Moringa + potato, and d. Moringa + mustard.

Rainy (Kharif) season crops viz., mungbean “Samrat”, and cowpea “Kashi Kanchan” were sown with the seed rate of 12 and 20 kg/ha, respectively during the first week of July each year. The seed of both the crops was sown at a spacing of 30 × 10 cm in the alleys of fruit trees. Each crop was fertilized with 25 kg nitrogen, 50 kg phosphorus, and 40 kg potassium per ha. The experiment was conducted under rainfed conditions without any supplemental irrigation during the rainy season. The standard practice for plant protection against insect pests and diseases was followed. Mung bean matures in 55 – 60 days after sowing (DAS), whereas green pod of cowpea was ready for harvest within 50 – 55 DAS, subsequently-three plucking of pods were done at 10 days interval.

During the winter season, mustard “PM 28” and potato “Kufri Chipsona 1” were grown in alleys. Mustard was sown with 5 kg seed /ha with 30 × 10 cm planting geometry and the seed rate of potato remained 2,500 kg/ha tubers at 60 × 15 cm spacing. Litterfall from all fruit trees was collected and measured by placing the litter in 1 m2 litter traps under each tree facing all four directions for 12 months. Finally, the litterfall was weighed, air-dried, and then oven-dried to assess the total litterfall.

Growth and yield measurement

The growth, yield attributes, and yield of all crops were recorded periodically. Water supplied both through irrigation and rainfall under different systems was considered. The details of experimentation and the inputs involved were recorded separately for all systems, including the cost of seeds, fertilizers, and mechanization. Similarly, all output products like crops, fruits, fuel, etc. were also recorded. The observations on growth parameters (AGR = Absolute growth rate (represent the actual biomass production between two-time scale), CGR-Crop growth rate (closely linked with solar radiation interception), LAI = Leaf area index) in different intercrops were taken at the most critical growth were estimated with the Eqs. (1), (2), (3).where h1 and h2 are plant height at t1 and t2 times, respectively.where w1 and w2 are the plant weight at time t1 and t2, respectively.

The fruit trees were regularly pruned during the winter season and twinges were weighed and recorded. All the produces from different trees and seasonal crops were converted in monetary terms (US$) for comparison. For estimating the economic benefits, the average cost of inputs and outputs over the years was considered, either the Government prices (MSP) or the local market rates depending on the product and/or service. The year-wise total cost and total returns per hectare were estimated for each AFS to draw the inference of the benefit: cost ratio.

Calculation of system productivity and production efficiency

The mustard equivalent system productivity (MESP) was estimated by comparing the efficiency of different AFSs. For estimating equivalent yields, the prevailing market price and minimum support price (MSP) were considered. The MESY was calculated following Eq. (4).

where MESY mustard equivalent system productivity (Mg/ha) MY is the mustard seed yield (Mg/ha); Yi is the economic production of the ith crop (Mg/ha); Pi is the market price of the ith crop (US$/Mg) and Pm is the market price of mustard (US$/Mg).

Production efficiency (PE) was computed following Eq. (5).

Calculation of water use indices

Water use efficiency (WUE) of the crops under different treatments was computed by dividing the economic yield (kg/ha) by the total consumptive use CU (mm) from the respective plots (Eq. (6)) while irrigation water use efficiency was calculated by dividing the economic yield (kg/ha) with the total irrigation water applied (Eq. (7)). To assess the water use efficiency in monetary terms, monetary water use efficiency (MWUE) was estimated by dividing the economic returns (US$/ha) by water used (Eq. (8)).

Economic analysis

The economic analysis of the various fruit tree-crop combinations was performed to judge the economic viability of different production systems. The input cost was estimated based on the prices of input used and specific management practices adopted. The gross returns were estimated by the market value of the different products obtained. The monetary expenses are borne and the economic benefits from all the crops including fruit trees and systems were expressed in US$. The system net returns (SNR), benefit-cost (B:C) ratio, system profitability (SP), and relative economic efficiency (REE) were estimated using the following equations (Eqs. (9), (10), (11), (12)).whereas NRd net returns through a diversified system; NRe net returns through the conventional system.

Sustainable yield index (SYI)

A sustainable yield index (SYI) is a reckonable degree to measure the sustainability of a production system. Minimum yield under each system as against the maximum yield observed over the years can be assessed through the SYI. The SYI was computed with the following Eq. (13).where Ya is the mean yield (Mg/ha), α is the standard deviation of the yield, and Ym is the maximum yield (Mg/ha) observed under a set of management practices (Shekhawat et al., 2016).

Estimation of carbon sequestration potential and carbon sustainability index

Carbon sequestration potential (CSP) represents an annual increase in the C stock through a system under a particular management practice from the base value. In the present study, the C sequestration was estimated in terms of increment in C stock in the soil under different AFSs. The values for initial and final SOC concentrations under different AFSs were obtained for all plots, and the CSP was calculated following Eq. (14) (Shekhawat et al., 2016).

The mass of SOC (MSOC) in two soil depths (0–15, 15–30 cm) was estimated and expressed in Mg/ha as follows (Eq. (15)).where SOC is in %, pb is the bulk density (Mg/ m3), and T is the thickness of the surface soil layer (cm).

The carbon sustainability index (CSI) was computed as the quantity of “C” amassed or created as biomass against a unit of C emitted as greenhouse gasses into the atmosphere during the crop season. The CSI was computed using eq. (16) (Lal, 2004).whereas CSI is the carbon sustainability index, Co is the sum of all outputs expressed in C equivalents, Ci is the sum of all inputs expressed in C equivalents and t is the time in years. A system with a higher CSI will be considered more C-efficient than those with lower CSIs.

Statistical analysis

The experimental data were analyzed with descriptive statistics and one-way ANOVA at a significance level of 0.05. To compute the differences among the means, a post hoc test was performed using Duncan's Multiple Range test at a significance level of 0.05 using Statistical Package for Social Science (SPSS) version 20.0.

Results

Growth of seasonal crops in the association with perennial trees

Irrespective of tree-crop associations, the maximum AGR was observed in mustard (0.60 g/day) while the minimum was observed for mung bean (MB) (0.18 g/day). Concerning mean AGR, mustard showed the maximum AGR value (3.83 g/day) while cowpea (CP) had the lowest mean AGR (Table 2). Similarly, the crop growth rate (CGR) of annual crops also varied with tree types. All the crops recorded higher CGR(g/m2/day) with moringa association. Among the various annual crops, MB had the highest CGR (12.30 g/m2/day) whereas, mustard had the lowest CGR (6.83 g/m2/day). Among the different combinations, the CGR of all the annual crops was maximum with moringa association. LAI varied significantly among the crops, it was 0.9 for the potato, whereas LAI remained higher (3.4) for the mustard crop, which persisted at maximum (LAI 3.6 ± 0.17) under moringa-based AFS. The LAI range was greater in CP (1.35 – 2.1) and less varied in other field crops (Table 2).

Table 2

Physiological attributes of annual crops under different integrated agroforestry systems.

Growth parameters	Crops	Karonda based AFS	Phalsa based AFS	Moringa based AFS	Guava based AFS	Mean	Range
AGR (g/day)	Mung Bean (40–45 DAS)	2.32 ± 0.15	2.42 ± 0.16	2.50 ± 0.09	2.34 ± 0.18	2.40	0.18
	Potato (40–45 DAS)	2.45 ± 0.04	2.5 ± 0.05	2.67 ± 0.08	2.4 ± 0.05	2.51	0.27
	Cowpea (40–45 DAS)	1.8 ± 0.10	1.90 ± 0.07	2.2 ± 0.09	1.95 ± 0.08	1.96	0.40
	Mustard (45–50 DAS)	3.6 ± 0.20	3.5 ± 0.23	3.8 ± 0.24	3.2 ± 0.24	3.53	0.60
CGR (g/m2/day)	Mung bean (20–40 DAS)	11.8 ± 0.77	11.5 ± 0.80	13.1 ± 0.84	12.8 ± 0.75	12.30	1.60
	Potato (30–60 DAS)	9.5 ± 1.12	10.6 ± 1.0	11.4 ± 1.10	8.9 ± 0.95	10.10	2.50
	Cowpea (20–40 DAS)	10.5 ± 1.02	11.5 ± 0.90	12.8 ± 0.85	10.8 ± 1.1	11.40	2.30
	Mustard (30–60 DAS)	6.4 ± 0.76	6.8 ± 0.8	7.9 ± 0.95	6.2 ± 0.75	6.83	1.70
LAI	Mung bean (45 DAS)	1.6 ± 0.12	1.7 ± 1.1	1.84 ± 0.90	1.58 ± 0.85	1.68	0.26
	Potato (45 DAS)	0.85 ± 0.14	0.87 ± 0.15	1.1 ± 0.16	0.79 ± 0.14	0.90	0.31
	Cowpea (45 DAS)	1.35 ± 0.31	1.8 ± 0.30	2.1 ± 0.28	1.7 ± 0.24	1.74	0.75
	Mustard (45 DAS)	3.2 ± 0.16	3.4 ± 0.17	3.6 ± 0.17	3.4 ± 0.18	3.40	0.40

±SD = standard deviation, AFS = Agroforestry systems, DAS = Days after sowing, AGR = Absolute Growth Rate, CGR-Crop Growth Rate, LAI = Leaf area index.

Economic productivity

Among fruit trees, the highest fruit yield was obtained from phalsa (13.4 – 14.5 Mg/ha) followed by moringa (12.4 – 13.0 Mg/ha) while guava remained the least productive fruit tree (Table 3). Among the different combinations of mungbean (MB) with tree crops, cultivation of MB with phalsa during rainy season crops resulted in maximum MB productivity (0.8 Mg/ha). Concerning cowpea (CP), integration of CP with karonda recorded maximum green pod yield (7.5 Mg/ha) followed by a moringa-based system. In totality among the rainy season crops cultivation of CP along with phalsa resulted in significantly higher production efficiency (56.3 kg/ha/day). Similarly, a combination of tree crops with winter season crops had a significant impact on the productivity of mustard and potato. The integration of trees had a significant impact on the tuber yield of potatoes. Cultivation of potato with moringa recorded maximum potato tuber yield (22.5 Mg/ha) however maximum seed yield of mustard (1.75 Mg/ha) was recorded with karonda. Similarly, maximum system production efficiency (214.3 kg/ha/day) of winter crops along with fruit trees was recorded with the moringa-based system. While assessing the year-round productive capacity of different systems, phalsa + MB - potato recorded maximum system productivity (25.9 Mg/ha), system production efficiency (101 kg/ha/day) followed by phalsa + CP - mustard (Table 3). Although all the tree-crop combinations recorded significantly higher system productivity over the fallow-mustard system. With regards to the sustainable yield index (SYI), among all combinations, phalsa + MB - potato recorded and moringa + MB - potato systems had the maximum SYI (0.87). Both the systems recorded 36% higher SYI over the fallow-mustard system (business as usual).

Table 3

Productivity of different integrated agroforestry systems (Av. of 03 yrs.).

Fruits component	Fruit yield (Mg/ha)	Kharif (rainy) season				Rabi (winter) season				System productivity and sustainability
		Seasonal crops	Green Pod yield (Mg/ha)	Seed Yield (Mg/ha)	PE (kg/ha/day)	Seasonal crops	Tuber yield (Mg/ha)	Seed yield (Mg/ha)	PE (kg/ha/day)	SP (Mg/ha)	SPE (kg/ha/day)	SYI
Karonda based system	5.0b	MB	–	0.6b	16.7d	Potato	22.0	–	209.5a	16.5c	76c	0.83a
	5.6b	CP	7.5a	–	35.6b	Mustard	–	1.75	14.9b	14.7c	40d	0.68ab
Phalsa based system	14.5a	MB	–	0.8a	41.7ab	Potato	21.4	–	203.9a	25.9a	101a	0.87a
	13.4a	CP	7.2a	–	56.3a	Mustard	–	1.64	14.3b	21.2b	61c	0.79a
Moringa based system	13.0a	MB	–	0.7ab	37.5b	Potato	22.5		214.3a	10.4d	99b	0.87a
	12.4a	CP	7.4a	–	53.7a	Mustard	–	1.71	14.9b	6.9e	59cd	0.78a
Guava based system	2.2c	MB	0.0	0.7ab	6.8d	Potato	21.1	–	201a	8.0d	66c	0.80a
	1.6c	CP	7.1a	–	23.8c	Mustard	–	1.71	15.2b	4.7ef	29d	0.55b
Fallow-Mustard system			–	–	–	Mustard		1.90	15.8b	1.9g	–	0.55

Different lower-case letters indicate significant differences (P = 0.05) among the different agroforestry systems; MB: mung bean; CP: cowpea; PE = Production efficiency; SP: System productivity; SPE: System Production Efficiency; SYI: Sustainability Yield Index.

Economics returns

Among the different tree-crop combinations during the rainy season, a combination of karonda + cowpea resulted in significantly higher net returns (1977.5 US$/ha), B:C ratio (3.90), and profitability index (5.42 US$/ha/day) followed by moringa + cowpea system (Table 4). However, during the winter season moringa + potato system registered maximum net returns (2156.1 US$ /ha), B:C ratio (2.63), and profitability index (20.53 US$ /ha/day) followed by the karonda + potato combination (Table 4). Concerning to year-round economic profitability of different tree-crop combinations, the karonda + MB-potato system recorded the highest system net returns-SNR (3,529.1 US$/ha) followed by the moringa + MB - potato system (3119 US$/ha). However, a significantly higher B:C ratio (3.85) was obtained with the karonda + CP - mustard system but it remained statistically at par with the karonda + MB - potato system (3.0). Concerning economic performance concerning conventional systems i.e. relative economic efficiency (REE), all the tree-crop combinations recorded higher REE. Among the diversified system, the karonda + MB - potato system had higher REE followed by the phalsa + MB - potato system. The karonda + MB - potato system recorded higher 96.7% higher economic returns than the fallow - mustard system (Table 4).

Table 4

Economics of different integrated agroforestry systems (3 yrs. avg.).

Fruits component	Kharif (rainy) season				Rabi (winter) season				System profitability
	Seasonal crops	NR (US$/ha)	B:C ratio	Profitability index (US$/ha/day)	Seasonal crops	NR (US$/ha)	B:C ratio	Profitability index (US$/ha/day)	SNR (US$/ha)	B:C ratio	Relative economic efficiency (US$/ha/day)
Karonda based system	MB	1,480.2b	3.73a	4.05ab	Potato	2,089.9a	2.55a	19.91a	3,529.1a	3.00ab	9.67
	CP	1,977.5a	4.90a	5.42a	Mustard	632.3b	1.99ab	5.50c	2,625.7b	3.85a	7.20
Phalsa based system	MB	990.7d	2.58b	2.71bc	Potato	2,023.8a	2.47a	19.27a	3,054.2a	2.62b	8.37
	CP	1,267.2c	3.25ab	3.47b	Mustard	593.9b	1.87b	5.16c	1,883.6c	2.82b	5.16
Moringa based system	MB	923.3d	2.41b	2.53bc	Potato	2,156.1a	2.63a	20.53a	3,119.0ab	2.68b	8.54
	CP	1,296.3c	3.32ab	3.55b	Mustard	632.3b	1.99ab	5.50c	1,949.7bc	2.92b	5.34
Guava based system	MB	422.0e	1.06c	1.16cbc	Potato	1,970.9a	2.4a	18.77b	2,493.4b	2.12c	6.83
	CP	869.1d	2.15b	2.38	Mustard	654.8b	2.06ab	5.69c	1,496.0c	2.20c	4.10
Fallow-mustard system	–	–	–	–	Mustard	633.6b	1.80b	5.3c	633.5d	–	–

Within a column, values represented with different lower-case letters indicate statistically significant differences (P = 0.05). MB: Mung Bean, CP: Cowpea; NR: system net returns, B:C ratio: Benefit: Cost ratio.

Water use dynamics

Rainy season crops (cowpea and mung bean) were grown under the rainfed condition with lifesaving irrigation. However, need-based irrigation was applied during winter season crops. During rabi (winter season), water use with the inclusion of various field crops under fruit trees was 1356.60 mm with potato and 1296.60 mm with mustard (Fig. 3). Among the different combinations, cultivation of mung bean during the rainy season and potato during the winter season with phalsa registered maximum water use efficiency (WUE, 19.10 kg/ha-mm), while maximum IWUE was in phalsa + CP - mustard (88.33 kg/ha-mm) followed by the karonda + MB - potato system for WUE 12.0 kg/ha-mm, whereas higher IWUE (61.25 kg/ha-mm) was in the karonda + MB - mustard system.

Fig 3

Water use efficiency (WUE), monetary water use efficiency (MWUE), irrigation water use efficiency (IWUE), and total water use under diverse integrated agroforestry systems. mung bean (MB), cowpea (CP).

Concerning MIWUE, integration of karonda with cowpea during the rainy season and potato during the winter season gave the highest MIWUE (12.71 $/ha-mm), followed by karonda + MB - mustard integration (11.30 US$/ha-mm), while guava integration with CP-mustard registered the lowest MIWUE (6.73 US$/ha-mm). Similarly, the next best combination in terms of MWUE was phalsa integration with MB - potato registered significantly higher monetary water use efficiency (MWUE) (10.99 US$/ha mm) followed by phalsa + MB - mustard integration (Fig. 3).

Soil organic carbon dynamics

After three years of fixed plot study, maximum SOC was registered under the phalsa + CP - mustard system (0.41%), and moringa + MB - potato (0.41%) followed by moringa + CP - mustard (0.40%) systems after three years of experimentation (Fig. 4). However, the lesser SOC storage (0.32%) was recorded in soils under guava + based AFS (CP-mustard) in the upper 0–15 cm soil layer. Similarly, even in deeper soil layers (15–30 cm), the SOC remained at an almost equal level (0.33% and 0.32%) under karonda + MB - potato and karonda + CP - mustard AFSs respectively. Whereas the mass of SOC, with higher SOC density) was observed in soils under phalsa (9.10 Mg/ha and moringa (9.16 Mg/ha), based on AFSs with the inclusion of CP - mustard and MB - potato.

Fig 4

Change in soil organic carbon (%) after three years of integrated agroforestry systems. MB: Mung bean; CP: Cowpea

Among different tree-crop combinations, the maximum potential for carbon sequestration rate was observed for phalsa-based AFS (Fig. 5). The higher CSP (0.48–0.73 Mg/ha/year) was observed in the soil at a depth of 0–15 cm, whereas declining relatively (0.4–0.62 Mg/ha/year) in the lower soil layer (15–30 cm). Phalsa-based AFSs were recorded with higher CSRP owing to enhanced biomass accumulation in the soil. CSRP was higher under phalsa-based AFSs in the 15–30 cm soil layer than in surface soil (0–15 cm) of karonda, moringa, and guava-based AFSs (Fig. 5). Under the guava-based system, the minimum carbon sequestration was obtained. However, among the tested tree-crop combinations, in terms of carbon sequestration capability, the moringa-based system was the second-best option for sequestering more C in soil and regulating the C emission from the soil. Finally, the CSI was higher under the moringa + CP - mustard system 27.6, followed by the moringa + MB - potato (27.3) system (Fig. 5).

Fig 5

Carbon sequestration potential rate (Mg/ha/yr) (CSP) and carbon sustainability index (CSI) under tree-crop combination, mass of soil organic carbon (Mg/ha) (MSOC) after three year testing of diverse integrated agroforestry systems.

Discussion

The rational combination of fruit trees with crops (AFSs) is a resource-efficient and sustainable method to combine production and resource conservation (Yadav et al., 2021b). They are structurally and functionally more intricate than silvicultural and agricultural monoculture systems (Rathore et al., 2021). AFSs allow the improvement of biodiversity (Bradley et al., 2012, Cardozo et al., 2015) nutrient cycling, and soil health build-up (Nair et al., 2010), without compromising farm productivity (Yadav et al., 2021b). Nevertheless, tree-crop combinations can escalate the proficiency of land use (Babu et al., 2020, Yadav et al., 2021a) and boost economic and ecological advantages (David et al., 2013). Karonda, a multipurpose, hardy evergreen, small fruit plant (up to 3 m in height) ability to produce higher economic yield with fewer inputs even under extreme climatic conditions, grows successfully on marginal lands, makes karonda a suitable option under AFS (Bhandari et al., 2014, Singh et al., 2018). Phalsa- a short stature hardy semi-wood perennial plant can potentially grow in low fertilized soil and moisture limitation conditions. Similarly, owing to its multipurpose (Ashfaq et al., 2012), fast-growing lower nutrient and water demand moringa is a suitable tree (Daba 2016) candidate for the tropical and subtropical world (Mridha and Al-Barakah 2017). A considerable amount of soil N fixation due to leaf fall (Munroe and Marney, 2013, Solanki and Arora, 2015) and added dry matter after pruning enhanced soil fertility which improved the growth and productivity attributes of seasonal crops grown in the alleys (Foidl et al., 2001, Melesse et al., 2012). Moringa, in alley cropping systems, promotes the growth of intercrops by adding N-rich plant biomass (Bamishaiye et al., 2011). Though moringa also helps in soil health build-up, it has more foliage coverage than karonda, and hence its shading effect create obstacle to the growth and spread of annual crops (Melesse et al., 2012, Sanchez et al., 2006). The moringa tree canopy is umbrella-shaped with bi-(tri-) pinnate leaves and the individual leaflets have a leaf area of about one to two cm2, leading to a higher canopy area than others (Quintin et al., 2011). In the present study, lesser interference between the trees and the developing field crops under these AFSs was observed, which is reflected in enhanced dry matter accumulation (Roberto et al., 2020, Jose, 2009), higher LAI, CGR, and AGR of the field crops under moringa and karonda based systems (Table 2).

In the present study, the phalsa + MB - potato and karonda + MB - potato systems gave higher system productivity over others. Inclusion of potato during rabi season in karonda + MB recorded 21.6% higher system productivity over mustard cultivation in the same system. The synergy between the two crops led to higher system productivity in AFSs (Swieter et al., 2021). However, guava based system had the lowest farm productivity. Lesser system productivity in the guava-based system was mainly attributed due to poor crop performance and poor fruit yield of guava as compared to other counterparts, which may be due to allelopathic interaction (Batish et al., 2008, Gill et al., 2000). A more interesting current finding suggested that the sustainable yield index (SYI) was almost the same under the phalsa + MB - potato and moringa + MB - potato system but significantly higher over other systems. This indicates that the cultivation of annual crops namely mungbean-potato in system mode with phalsa and moringa is a suitable and productive option for the semi-arid region (Vladimir et al., 2021). Higher system productivity was attributed due to higher intercrop yield and minimum competition for nutrients and water resources (Fisher et al., 2010, Das et al., 2022). The tree-crop association models also have a direct impact on the livelihood of the farmers (Armengot et al., 2016) which is evident from the enhanced economics of the system (Miah et al., 2018). This was probably due to higher space in alleys of phalsa than others resulting in a minimum interruption in solar radiation provision to the component crops. Also, a good amount of detritus material was continuously accumulated on the soil surface consequently increasing the SOC in the soil (Dhanya et al., 2013, Rathore et al., 2022). Concerning economic returns, in the present study karonda + MB - potato system recorded higher system net returns. High net returns in this particular system were mainly attributed due to the higher sale price of products and productivity (Dwivedi et al., 2007, Singh et al., 2018). In the present study, all the designed tree-crop-based production systems were more productive, profitable, and resource-efficient. From an economic point of view, increasing production through optimal strategies of diversification of land use can lead to a growth in unit costs, and at the same time reduce the quantity produced of every single product (Paul et al., 2017). Furthermore, multiple crops may also cut average production costs (Yadav et al., 2021a, Singh et al., 2021a), for the “economies of scope” (Martin and van Noordwijk, 2009). Despite the higher net returns under the karonda + CP - potato system the, higher B:C ratio was observed with the MB - mustard integration with karonda. This was mainly attributed due to more cultivation costs of different crops, especially potatoes. Higher potato raising cost under different intercropping scenario was also reported by other researchers (Lyngbaek et al., 2001, Arnold, 2018). Our study indicated that among the tested tree crop combinations, karonda and moringa-based production systems especially karonda + MB - mustard and moringa + CP - mustard are the best systems for enhancing farm profitability. Besides improving the resource use efficiency and pumping more carbon into the soil pool.

Conditions of scarce water availability and water competition between species can limit the growth of agroforestry probability, especially in conditions of low drought or poor soil conditions. Higher WUE and IWUE for phalsa + MB - potato and moringa + MB - potato than other AFSs were mainly related to the prudent water use by crops, resulting in enhanced plant growth and productivity. Higher productivity, profitability, and WUE from different crop combinations under moisture scare conditions have been previously reported by several workers (Sharma et al., 2013, Singh et al., 2018, Singh et al., 2021a). Thus, the study indicated that the inclusion of MB and potato with fruit trees like karonda and moringa under AFSs potentially enhanced the system productivity, income, and system sustainability under a semi-arid climate with a limited water supply. This is a vital factor in AFS stability and productivity (Iglesias and Garrote, 2015, Fan et al., 2018).

The inclusion of cash crops like potatoes enhanced net returns over mustard in AFSs. However, the low cost of cultivation of mustard in the potato system (Rathore et al., 2014) can be also explained by the reported higher WUE of the mustard crop under moisture-limited conditions (Rathore et al., 2019). Hence, the monetary expenditure ability of the growers also decides the profitability of a particular production system. Maximum monetary return per mm of water used, karonda + cowpea - mustard AFSs. The highest water use under various AFSs was recorded with potato as an intercrop, while only 120 mm of water was enough for mustard under limited moisture regimes (Rathore et al., 2020, Li et al., 2021). Therefore, a longer-duration crop like potato consumes 400–500 mm of water through the soil profile (Hatfield and Dold, 2019). Under rainfed situations, supplementary irrigation was applied in the system during Rabi (winter season) only to maintain the soil moisture above 50% of the available water range to avoid the anticipated yield losses when the moisture depletes below 50% of the total available soil water (FAO, 2008). This was the reason for enhanced WUE and MWUE (Rathore et al., 2020).

Soil C sequestration capacity of a production system is mainly regulated by planting arrangement, species diversity, nature of tree and crop species selected for cultivation, soil inherent capacity, climatic condition, and crop management practices (Montagnini and Nair, 2004, Nair et al., 2009). In this context, the AFSs including perennial trees reported to enhance C sequestration, offset global warming potential, and neutralized the C emission generated by other farming enterprises like animal production (Jose and Sougata, 2012, Rizvi et al., 2019). This is of particular significance because SOC regulates the global C emission and environmental quality (Nair et al., 2010, Doddabasawa et al., 2019). Tree-based crop production system generates a huge quantity of biomass with diverse quality which enhanced the CSRP. Although carbons sequestration decreases with soil depth this was attributed due to most of the crop and plant detritus remaining on the soil surface (Yadav et al., 2020, Das et al., 2022, Rathore et al., 2022). Phalsa needs severe pruning for fetching higher fruit yields. The heavy pruning produced a huge amount of biomass, in the present study entire pruned biomass of phalsa remained on the soil surface, which increase the C gain and CSRP of phalsa based system as compared to other production systems. Higher C gain under a tree-crop-based system over other systems was reported in many studies (Oelbermann et al., 2004, Mutuo et al., 2005). The carbon sustainability Index indicates the C sustaining ability of a particular system and conversion of C from the biomass, was also higher under a tree-crop-based system over a fallow-mustard system in the present study. Thus, the role of AFSs in C sequestration could pave the way to stabilizing GHG emissions (Rizvi et al., 2019). Kuyah et al., (2019) also reported that suitable AFSs reduce trade-offs between provisioning and regulating/maintenance services under arid conditions. C sequestration under tree-based systems could be enhanced in a short period by growing potential crops in alleys than in mono-cropping systems (Udawatta and Jose, 2011, Yadav et al., 2021b).

Policy implications

The globally semiarid region accounted for ∼15% of the earth's surface and supports about 14.4% population (Huang et al., 2016). While, India accounted for ∼148 Mha area (∼45% of total land area) under the semi-arid region. India’s semiarid region is densely populated and home to ∼520 million population (Singh et al., 2013). The agricultural productivity of a semi-arid climate is severely impacted by changing climate (Singh et al., 2013), and the unsustainable use of natural (Asplund et al., 2014). Semiarid regions are characterized by high spatial and temporal variability, poor soil fertility, and low rainfall (Snyder and Tartowski 2006). Despite the various sensitivity, the semi-arid agri ecology played a crucial role in food, livelihood security, and overall climate modulation. Therefore, it is vital to develop sound and robust agricultural planning to improve the well beings of the semi-arid populace and improve overall environmental security. To conserve natural resources and enhance the livelihood of smallholders Government of India initiated the National agroforestry policy in 2014 (Chavan et al., 2015). With regards to mitigation impact, the agroforestry systems in India have been estimated remarkable carbon sequestration potential of ∼25 Mg C per ha (Yadav et al., 2021b). Hence, there is tremendous potential to increase C storage in semi-arid soil by developing location-specific agroforestry systems. Agro-forestry landscapes contribute to multiple crucial roles to restore ecosystem services and sustain biodiversity and quality of life (Bugalho et al., 2018, Rathore et al., 2022). Results of the present study suggested that the adoption of integrated agroforestry systems increased farm productivity by ∼2–13 times besides doubling the C sequestration over the usual agricultural business in semi-arid regions. Perennial fruit trees are associated with annual crops under integrated agroforestry systems that create mixed plantations (Wei et al., 2016) that effectively improve the microclimate of agricultural land and the microenvironment. Indeed, the diverse crops with variable input requirement, like water, nutrients, light, etc., also minimizes resource competition and ensure complementary of resource use (Li et al., 2021). Results also suggest that the development and adoption of the location-specific integration of fruits trees with short-duration pulses, oil seeds, and vegetables is an environmentally clean and economically robust model that can potentially address the twin challenges to feed the galloping population and mitigate climate change, hence qualify to be a perfect model of climate-smart or green farming in the semi-arid ecologies.

Conclusions

The present study affirms that the synergistic tree-crop integration (mung bean, cowpea, mustard, and potato) has potentially improved farm productivity, profitability, and soil health with minimum environmental footprints and thereby, improving livelihoods. The data presented in the present study supports the following conclusions:

Phalsa + mung bean(MB) - potato/mustard resulted in maximum system productivity (25.9 Mg/ha and 21.2 Mg/ha) followed by a karonda-based system. However, the karonda + MB - potato system gave the maximum net system return (3529.1 US$/ha) followed by the moringa + MB - potato system (3119 US$/ha).

The karonda + cowpea-mustard system had the maximum benefit-cost ratio (3.85) followed by the karonda + MB-potato system (3.0). However, guava based system had the lowest B:C ratio.

Phalsa + MB - potato system gave the highest water use efficiency-WUE (33.0 kg/ha-mm) and irrigation water use efficiency-IWUE (203.9 kg/ha-mm). However, monetary water use efficiency-MWUE was the highest in the karonda + cowpea - mustard system (23.6 US$/ha-mm).

Phalsa-based AFS has the highest carbon sequestration potential (0.6–0.67 Mg/ha/year) and the lowest C footprint (20–50% less than other AFSs).

The tree-crop-based production systems involving fruit trees like karonda, moringa, and phalsa with mung bean, cowpea in the rainy season, potato, and mustard during the winter season are productive, profitable, environmentally clean, and resource-efficient production under moisture-limiting semi-arid conditions. Thus, in the changing climatic context, tree-crop-based production systems can represent a practical strategy to foster the sustainability and resilience of agriculture under semi-arid condition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.