Rice Equivalent Yield and Soil Properties as Influenced by Conventional and Minimum Tillage System in Rice Based Cropping Sequence in North-East India.

The minimum disturbance of soil is gaining popularity in different parts of the world because of definite advantages over conventional tillage (CT) especially with respect to rice cultivation. Conventionally, rice is transplanted in puddled soil in which soil is completely broken down and destroyed in presence of standing water to create an impervious layer below the surface so as to hold the rainwater for the rice. Such practice noticeably hampers the growth of the succeeding winter crop grown under conventionally tilled soil because of alteration of soil physical characteristics. Taking into consideration, a field experiment was conducted from 2016 to 2019 to assess the alterations in soil properties resulting from various tillage systems in the cultivation of rice followed by Indian mustard, either through transplanting or direct seeding, after the cultivation of Sesbania aculeata. The experiment was conducted with 20 treatment combinations comprising of five tillage practices combining minimum tillage (MT) and conventional tillage (CT) viz., T1: CT (S: Sesbania)-CT (TR: Transplanted rice)-CT (IM: Indian mustard), T2: MT (S)-CT (TR)-MT (IM), T3: MT (S)-CT (DSR: Direct seeded rice)-CT (IM), T4: MT (S)-MT (DSR)-MT + rice residue @1.5 tha−1 (IM), T5: MT (S)-MT (DSR)-MT (IM) and four weed management practices viz., W1: recommended herbicides (S and IM: pendimethalin 0.75 kg ha−1 pre-emergence; rice: pretilachlor 0.75 kg ha−1 pre-emergence) W2: IWM: integrated weed management (W1 + manual weeding), W3: manual weeding/hoeing, W4: weedy check, laid out in a split-plot design with tillage practices in the main plots and weed management practices in the sub-plots with three replications. Weed management is excluded from the results and discussion section of the paper due to no treatment effect on soil properties. The soil properties studied under the investigation were microbial population, microbial biomass carbon, soil enzymes such as dehydrogenase, phosphomonoesterase and fluorescein di-acetate, soil available NPK, soil organic carbon, bulk density, water holding capacity, total porosity, water stable aggregates, and mean weight diameter of aggregates were significantly changed under direct seeded rice based system as compared to puddled rice based system. Findings of the experiment suggested that by minimizing soil disturbance and residue retention in winter crop not only improved soil properties but also system productivity in terms of average rice equivalent yield (18.60%) of rice-Indian mustard cropping sequence over conventional tillage system. Minimum tillage in Sesbania-direct seeded rice-Indian mustard with rice residue retention improved macro water stable aggregates (> 0.25 mm sized aggregates) (62.08%) and mean weight diameter of aggregates (1.34 mm) at 0–30 cm soil depth as compared to conventional tillage system (60.04% and 1.27 mm, respectively). The same treatment improved total porosity and water holding capacity of 0–15 cm of soil depth by 47.42% and 45.87%, respectively as compared to conventional tillage after three years of investigation. Regression analysis shows that one unit reduction in bulk density increased total porosity of soil by 1.47 units; whereas a unit improvement in total porosity improved water holding capacity of soil by 1.25 units. Other soil properties viz., soil organic carbon (16.75% in 0–15 cm depth and 25.86% in 15–30 cm depth), available nitrogen, phosphorous and potassium (1.04%, 5.40% and 1.54%, respectively); bacterial and fungal population, microbial biomass carbon (49.90%), and activity of dehydrogenase, phosphomonoesterase and fluorescein di-acetate (25.39%, 17.02% and 48.94%, respectively) were also improved under the same treatment over conventional tillage system. A significant (P ≤ 0.01) positive correlation of soil macro-aggregates, water holding capacity, soil microbial biomass carbon with soil organic carbon as well as phosphomonoesterase, dehydrogenase and fluorescein di-acetate activities with soil microbial carbon was observed. [ABSTRACT FROM AUTHOR]