Vol. 15 No. 1
Soil microbes, nutrient removal, productivity and profitability of lentil (Lens culinaris Medikus) influenced by weed management practices
Abstract: A field experiment was conducted during winter (Rabi) seasons of 2012-13, 2013-14 and 2014-15 in sandy loam soils of Central Brahmaputra Valley Zone (CBVZ) of Assam to study the effect of pre-emergence herbicides and their combination with hand weeding on weed growth, soil microbes, nutrient removal by both crop and weed, grain yield and economics of lentil (Lens culinaris Medikus ssp. culinaris) under irrigated conditions. Pendimethalin + imazethapyr (combo formulation) 1.0 kg ha-1 as pre-emergence (PE) + hand weeding (HW) at 40 days after sowing (DAS) and pendimethalin 1.0 kg ha-1 PE + HW at 40 DAS controlled weeds effectively and recorded 79.63 and 74.75 per cent weed control efficiency (WCE), respectively. These two integrated weed management practices exhibited significant superiority to pendimethalin as well as the combo formulation. After the initial suppression, the adverse effect of herbicides on soil microbial population was decreased from 25 DAS onwards, and microbial population gradually increased through the crop growing period. The increase in symbiotic N-fixing (NFB) and phosphate solubilizing bacteria (PSB) at harvest over initial values ranged from 106.1 to 151.9 per cent and from 115.4 to 146.1per cent, respectively. Uptake of N, P and K by crop was maximum under the combo formulation + HW (45.42, 3.32 and 5.54 kg ha-1, respectively). Pendimethalin 1.0 kg ha-1 + HW accrued in an uptake of 43.33 kg N ha-1, 3.17 kg P ha-1 and 5.28 kg K ha-1. However, nutrient (N, P, K) removal by weeds was minimum under these two treatments. These two weed management practices accrued in significantly higher (pooled) grain yields (1107.89 and 1056.72 kg ha-1, respectively) as compared to all other treatments. The benefit-cost ratio (BCR) under these two was 2.53 and 2.63, respectively. Considering the easy availability of pendimethalin in Assam, the technology ‘pendimethalin 1.0 kg ha-1 PE + HW at 40 DAS’ was tested for effective weed management, maximizing lentil production and farmers’ acceptability in farmers’ fields during Rabi 2015-16 through four Krishi Vigyan Kendras (KVK) in Upper Brahmaputra Valley (UBV), Central Brahmaputra Valley (CBV), Lower Brahmaputra Valley (LBV) and North Bank Plain (NBZ) Zones of the state. The yield increase over farmer’s practice (1 HW at 25-30 DAS) was 23.2, 46.6, 8.1 and 8.4 per cent in UBV, CBV, LBV and NBP, respectively.
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