Nitrogen management for wheat (Triticum aestivum L.) intercropped with variable aged poplar (Populus deltoides Bartr.) plantations in North-Western India.

Agroforestry system (AFS) is considered to be sustainable agricultural practice delivering wide range of ecosystem services. Nutrients and light are principal limiting resources for understorey crops. To optimize productivity, recommendation is to use well adapted tree–crop–fertilizer combinations. Nitrogen (N) management for wheat poplar is essential for maximizing synergies but the data is scarce. Therefore, current study addressed the issue by monitoring wheat performance fertilized with N: control (N1), 60 (N2), 90 (N3), 120 (N4), 150 (N5), 180 (N6) and leaf color chart (LCC) based-115 (N7) kg ha−1 under 2-, 3-, 5- and 6-year poplar. Tree age and N levels were key determinants of yield with reduction in growth (number of tillers m−1, plant height, ear length), yield parameters (1000-grain weight, number of grains ear−1), yield and NUE of wheat with advancing tree age, maximum reduction under 6-year plantation. However, fertilization with N7 −115 kg N ha−1 showed highest increase in grain yield (95.1%), harvest index (20.1%), NUE (agronomic efficiency (AE) 53.5% and recovery efficiency (RE)-91.1%). Nutrient uptake by grains showed maximum decrease of 32.1 (N), 13.6 (P) and 22.8 (K)%, respectively under 6-year-poplar. Averaged over poplar age, the N fertilizer treatment N7 lead to maximum increase of 2.3-, 2.9- and 2.3-folds in N, P, K uptake by grains, respectively. Therefore, the N management of wheat with N7 −115 kg N ha−1 (LCC-based treatment) under poplar tree canopies show the potential to mitigate the risk of poor crop yield and contribute to food security. [ABSTRACT FROM AUTHOR]