Rice Residue Load Influences the Wheat Crop Associated Weed Flora in Rice-Wheat System

Abstract

The high productivity of rice-wheat (RW) system under ‘Green Corridors’ of western India is on the cost of over exploitation of natural resources (soil, groundwater and energy) and excessive use of inputs (fertilizers, herbicides, pesticides, irrigation water etc.) with the conventional/traditional management practices. Furthermore, the situation will be more intensified with the expected climate change effects and population pressure in the near future. In the region, conservation agriculture (CA) practices are practicing as an alternative to the conventional system in RW system. These practices have shown direct role in improving the farm productivity and profitability, and in quality of soil and environmental while conserving natural resources (soil, water, energy) and delimiting the environmental footprints. The CA- based practices also have potential in suppressing the major weeds (Phalaris minor, Echinochloa crusgalli, E. colonum, Rumex dentatus, Chenopodium album, Anagallis arvensis) up to some extent in RW system. To evaluate the potential of CA- based system on weed suppression, a study was conducted in farmers’ participatory mode at Karnal. Results showed the lower weeds population in CA- based wheat system when it was planted early (3rd week of October) with full rice residue retention (average 6-8 Mg ha-1). Two-year results showed that population of major weeds like Phalaris minor, Rumex dentatus, Chenopodium album and Anagallis arvensis were reduced by 61-64, 41-70 14-32 and 43-68%, respectively in zero-tillage (ZT) plots where 6-8 Mg ha-1 and more rice crop residues were retained as compared to without residue (0.0 Mg ha-1). The combination of early sowing and full rice residue retention (8-10 Mg ha-1) reduced the P. minor population by 70-85% in wheat crop. The P. minor density under different CA-based practices was recorded in decreasing trend from 2020 to 2022 because of exhaustion of weed seed bank over the years and by the suppressing ability of crop residue mulch. The CA- based RW system could be a promising alternative for weed suppression in conveniently managed RW systems in northwest India.