Effect of Climate Change and Soil Management on Water and Nutrient Uptake for Sustainable Yield of Wheat Genotypes with Different Root Traits

Abstract

Drought and heat stress are the most important climate change factors decrease water and nutrient uptake and therefore negatively affect wheat growth. Surface soil drying decreased both water and NH4+ uptake from the top soil. However, increased water availability with bottom watering increased water uptake from the bottom soil layer, but not NH4+ uptake from the bottom soil layer. With surface soil drying, plants grew more and longer roots in the bottom soil layer, shifting water uptake from the top to the bottom soil, while N uptake was reduced in the top soil because of a decrease in root biomass. Drought stress and heat stress decreased the yield of all wheat genotypes, in particular 249, while combined drought and heat stresses had the most pronounced negative effect on plant biomass and grain yield. Decreasing soil water availability decreased plant-derived C to soil organic carbon (SOC) and microbial biomass through rhizodeposition. Wheat genotypes with smaller root/shoot ratios and thinner roots were more efficiently assimilating C to the grain, while genotypes with higher root/shoot ratios and thicker roots allocated more C belowground through rhizodeposition at the expense of producing more yield. Increasing water availability from 15 % to 25% and reducing air temperature 30 to 25 °C increased N uptake by plants thereby reducing overall N loss, and increased transfer of N from vegetative parts to grain. While crop rotation did not affect soil available N and P, AMF colonization in wheat was on average 60% higher after chickpea than after the canola rotation. Wheat yield after chickpea increased for genotype IAW2013, and was positively related to AMF colonization for both genotypes. N and P fertilization reduced AMF colonization and yield, but increased shoot biomass and leaf tissue N and P concentrations. Leaf δ13C decreased with increased yield, suggesting that higher yielding and AMF colonized plants were less water stressed.