Do we need more drought for better nutrition? The effect of precipitation on nutrient concentration in East African food crops.

Soil, inputs, and environmental factors such as weather control plant nutrient availability and nutrient content in food. Drought periods affect nutrient bioavailability. Nutrient transport within the plant and allocation of nutrients within organs of the plant is water dependent and therefore drought susceptible. This study compared Kapchorwa, Uganda and Teso South, Kenya that experienced drought during the second season in 2016. The main research questions were: (i) do droughts have an impact on the nutrient composition of food; (ii) is there a difference in nutrient concentrations in food based on their xylem or phloem mobility? Maize (Zea mays) grain (n = 62) and matooke (Musa acuminata) fruit samples (n = 90) in Kapchorwa, and maize grain (n = 61) and cassava (Manihot esculenta) tuber (n = 64) in Teso South were collected during a normal season (March-July) and drought season (October-December) in 2016. Crop samples were analysed using a pXRF for P, K, Ca, Mg, S, Fe, Mn, Cu, and Zn. The Standardized Precipitation Index (SPI) was calculated using TAMSAT database to compare drought intensities. The drought in Kapchorwa (SPI: -1.14 to -0.32) was severer and began 2 months prior to Teso South (SPI: 0.09 to 0.55). Nutrient concentration in Kapchorwa decreased significantly from normal to drought in both crops. In contrast, during the moderate drought in Teso South, nutrient concentrations increased significantly. Lacking nutrient phloem mobility is suggested to play a vital role in mobilisation of micronutrients (Fe, Mn, and Cu) as shown by their decreased concentration under severe drought in the yield. Total nutrients assimilated in crop samples were significantly higher in the normal than the drought for almost all samples. Micronutrients and yields during drought were strongly affected, leading to a double-burden for consumers through affected quantity and quality. Future research considerations should particularly include the focus on potential nutrient increases during mild drought.