Residual effects of weed biomass incorporation and nitrogen management in rice on the productivity of field pea in a rice-based cropping system

This research examines how managing nutrients in a rice crop affects the following field pea crop, a key question for sustaining rice-based systems in South Asia. In a two-year field study, conducted at the College of Post Graduate Studies in Agricultural Sciences, Umiam from 2023–24 to 2024–25, we tested the residual effects of two practices from the prior rice season: whether weed biomass was incorporated into the soil (5 t ha-1) or not and the application of nitrogen (N) fertiliser at five different rates (0–160 kg N ha-1). The results of the study showed that adding weed biomass consistently improved the field pea performance, resulting in taller plants, higher dry matter and higher crop growth rates (CGR). These benefits likely stem from the slow release of nutrients and improved soil conditions as the weeds decomposed. While adding N fertiliser boosted plant growth, the benefits peaked at 120 kg N ha-1, with no further gains at the higher rate of 160 kg N ha-1. The most significant results were seen in yield, where the combination of weed biomass and N worked together synergistically. This combination increased pod yield by 15 % compared to plots without incorporated biomass and achieved the highest overall yield. The practice also led to a slightly better harvest index, meaning plants were more effective at directing resources toward producing pods. In conclusion, for farmers, incorporating weed residues in rice and applying 120 kg N ha-1 to the rice crop creates a lasting positive effect, setting up the subsequent field pea for stronger growth and higher productivity in a more efficient cropping system.