Impact of sequential herbicides application on crop productivity, weed and nutrient dynamics in soybean under conservation agriculture in Vertisols of Central India.

Adoption of conservation agriculture (CA) is very slow due to weed infestations. The application of herbicides is the only viable option to deal with problem of weed management to adhere with basic principles of CA. A field experiment was carried out for three years to evaluate the expediency of different herbicides and their sequential applications under CA. In this study, seven treatments comprised of either alone or sequential application of pre-emergence (PE) and post-emergence (PoE) herbicides, hand weeding and weedy check were tested in soybean. Result indicated that sequential application of glyphosate at 1 kg ai ha-1 + pendimethalin at 1 kg ai ha-1as PE followed by PoE application of imazethapyr at 100 g ai ha-1 at 30 days after sowing (DAS) proved to be the best economical option in terms of plant growth parameters, crop biomass, seed yield, weed index and carbon and nutrient recycling. Pearson's correlation coefficients matrix revealed that grain yield was significantly (P<0.0001) related to weed density at harvest (r = -0.84), (WDH) (r = -0.63), weed dry biomass (WDB) (r = -0.52), weed nitrogen (N), phosphorus (P) and potassium (K) uptake (r = -0.56, r = -0.59 and r = -0.66), respectively and weed index (WI) (r = -0.96). The bivariate linear regression study of grain yield on weed control efficiency (WCI) biomass, N, P and K uptake by grain showed a clear significant (P<0.0001) dependence with R2 value of 0.53, 0.99, 0.95 and 0.98, respectively. The fitted stepwise multiple regression model also revealed that N and P uptake in grain, weed density at 20 DAS and K uptake in weed were actual predictor for grain yield. We concluded that, effective and economical weed control under CA in soybean can be achieved through sequential application of glyphosate along with pendimethalin at 1 kg ai ha-1 each PE followed by PoE use of imazethapyr at 100 g ai ha-1 at 30 DAS.

Agroforestry for controlling soil erosion and enhancing system productivity in ravine lands of Western India under climate change scenario.

Soil erosion in semi-arid climate leading to the development of ravine lands is the most severe form of land degradation. Ravine lands are formed when soil is not fully covered by the vegetation throughout the year and sporadic vegetation is not able to bind the soil particles from being washed away by rainfall. Throughout the globe, ravine lands have severe limitations for their rehabilitation and sustainable utilization as a consequence of its unique topographical features. Climatic and edaphic stresses make crop production extremely challenging in these lands. Practicing sole cropping promotes erosion, produces low crop yield, utilizes high energy, and emits greenhouse gasses (GHGs). Tree cultivation either sole or in combination with crops (agroforestry) has a strong potential to control erosion, produce sustainable economic yield, reduce energy consumption, and sequester greater amount of atmospheric carbon dioxide in biomass and soil carbon pools besides providing various ecosystem services. Therefore, practicing agroforestry could be a promising approach to obtain the greater environmental and economic benefits in the ravine lands. The present study was conducted on three systems, i.e., sole crop cultivation (cowpea + castor), agroforestry (sapota + cowpea + castor), and sole sapota plantation, to evaluate their impact on soil erosion, runoff, system productivity, profitability, energetics, and carbon sequestration during the 4-year period (2017-2020). The results revealed that agroforestry reduced the total soil loss and runoff by 37.7% and 19.1%, respectively, compared to the sole crop cultivation. Likewise, the highest system productivity as cowpea equivalent yield (CEY) was obtained under agroforestry system that increased the CEY by 162% and 81.9%, compared to sole crop and sole tree plantation, respectively. The climate change mitigation potential in terms of net carbon balance was observed highest in sole tree plantation (8.4 t/ha) followed by agroforestry system (5.9 t/ha) and lowest in sole cropping system (-2.8 t/ha). Therefore, an agroforestry system could be recommended for controlling soil erosion, improving system productivity and profitability, and reducing energy consumption as well as mitigating climate change in ravine lands.