Root System Size Influences Water‐Nutrient Uptake and Nitrate Leaching Potential in Wheat

Environmental and economic considerations require the effective use of water and nutrients to elevate grain production in bread wheat (Triticum aestivum L.) with concomitant reduction in nitrate leaching to minimize contamination of underground water. We determined the effect of the root system on leaching fraction, leachate N concentration, and N, P and K uptake using bread wheat 'Pavon 76' and its three near-isogenic translocation lines: Pavon 1RS. 1AL, Pavon 1RS.1BL and Pavon 1RS.1DL. These genotypes were grown in sand-tube experiments under optimum and low level of nutrients for 2 years. Root, stem and leaves, and grain N, P, and K content, and agronomic characters were measured. Leaching fraction and leachate nitrate concentration were measured at early tillering, booting and early grain filling. Significant main effects for year, nutrient level and genotype were found for the characters. Genotype x N interaction was significant only for root P content. Genotype x year interaction was significant only for plant N content, root P content and plant P content. Genotype × year × N interaction was significant only for root N uptake efficiency. Thus, genotypic means averaged across years and nutrient levels are reported. Low levels of nutrients (1330, 235 and 793 mg vs. 1915, 375 and 1268 mg N, P and K, respectively) reduced mean root biomass, plant biomass and grain yield by 27 %, 25 %, and 19 %, respectively. The translocation lines produced 31-46 % more root biomass, 11-14 % heavier grains and 6-8 % greater grain yield than Pavon 76. Leaching fraction was higher under low level of nutrient at booting and grain filling. Leaching fraction at tillering, booting, and grain filling was 67%, 42% and 25%, respectively. Leaching fraction at early tillering was lower for Pavon 1RS.1AL (39 %) and Pavon 1RS.1DL (40.5 %) than for Pavon 76 (45.3 %). Leachate nitrate concentration was lower for two translocation lines at all three stages of plant growth compared to Pavon 76. The correlation coefficient between plant N content and root biomass, between plant N content and plant biomass, and between grain yield and root biomass was positive and significant. Significant positive correlation was found between root biomass and P and K uptake. Multiple small applications of N fertilizer during early plant growth with adequate irrigation water are recommended. Wheat genotypes with superior root characteristics for efficient nutrient uptake, especially during tillering and booting, should be developed in breeding programmes to increase grain yield and to minimize the nitrate leaching.