Recovery of 15N fertilizer in intercropped maize, grass and legume and residual effect in black oat under tropical conditions

Abstract

The development of integrated crop-livestock systems (ICLSs) under no-tillage (NT) is of global interest for improving agroecosystem sustainability in tropical regions. In these crop systems, nitrogen (N) is the most essential nutrient. Nitrogen needs vary according to environmental conditions and crop rotation and are higher when crop succession is performed with grasses only. Intercropping maize with legumes is an interesting alternative to improve agricultural management and N cycling. To better understand N dynamics in ICLSs, in this study, two maize (Zea mays L.) silage production systems were developed: intercropping with palisadegrass (Urochloa brizantha ‘Marandu’, syn. Brachiaria brizantha) only or palisadegrass and pigeon pea [Cajanus cajan (L.) Millsp.] (summer–autumn). In both intercropping systems, black oat (Avena strigosa Schreb) was oversown and grazed by lambs (winter–spring). We assessed biomass production, N uptake, and fertilizer-N recovery due to the addition of 15N-labeled fertilizer in maize intercropped with palisadegrass and pigeon pea and the residual effect on black oat grazed by lambs during two growing seasons in a Typic Haplorthox in southeastern Brazil. The triple intercropped crops produced higher amounts of silage and pasture biomass and efficiently increased the use of N fertilizer by maize, thereby promoting greater 15N recovery. Palisadegrass and pigeon pea are a good option for cultivation in tropical regions, as this combination did not alter the measured levels of N in the intercropping systems but improved N dynamics, efficiency, balance, and N fertilizer distribution in the soil-plant system. This study provides a better understanding of N dynamics in the soil-plant system to support more efficient N fertilization in ICLS under NT.