Effect of inter-tillage weeding on rice yield, rice growth, and nutrient dynamics without agrochemical and fertilizer application: Results of a three-year study

Abstract

Traditionally, frequent inter-tillage is believed to increase rice yield without the application of chemicals. However, research on rice growth and soil nutrient dynamics under such cultivation management is lacking. In this study, we performed rice cultivation without applying agrochemicals and fertilizers to elucidate the influence of inter-tillage, especially, three years after switching to no chemical application. The rice growth, rice yield, and nutrient (N, P, and K) dynamics over three years (2018–2020) were assessed, including three different treatments: 0-, 2-, and 5-times inter-tillage (0-T, 2-T, and 5-T, respectively) and conventional cultivation as rough reference. In the first year, the brown rice yield in inter-tillage fields (531–566 g/m2) was higher than the regional average yield for conventional rice cultivation (497 g/m2) after several years of fallow with herbicide. In the second year, following nutrient consumption in the first year, the yield in inter-tillage fields (220–272 g/m2) was less than the regional average yield (547 g/m2). There was no significant variation (P < 0.05) in yields in the three inter-tillage fields in the first and second years. However, in the third year, the order of yield achieved in experimental fields was 5-T (354 g/m2) > 2-T (209 g/m2) > 0-T (173 g/m2), although these yields were lower than the regional average yield (561 g/m2). The exchangeable ammonium concentration in the soil and the ammonium concentration in the soil solution from inter-tillage fields decreased in the third year compared to the second year's results. However, the rice yield, growth, and nitrogen concentration in rice plants in 5-T increased in the third year. Our findings indicate that several years of inter-tillage make the soil environment effectively suitable for fertilizer- and chemical-free rice cultivation.