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Carbon retention is a critical issue in arable farming of the Indian Himalayas. This study, conducted from 2001 through 2010 on a sandy clay loam soil, evaluated the effect of tillage alterations (conventional tillage [CT] and zero tillage [ZT]) and selected irrigation treatments (I1: pre‐sowing, I2: pre‐sowing + active tillering or crown root initiation, I3: pre‐sowing + active tillering or crown root initiation + panicle initiation or flowering, and I4: pre‐sowing + active tillering or crown root initiation + panicle initiation or flowering + grain filling), applied at the critical growth stages to rice (Oryza sativa L.) and wheat (Triticum aestivum L.) on soil organic C (SOC) retention and its pools, soil aggregation, and aggregate‐associated C contents in the 0‐ to 30‐cm soil layer. Results indicate that the plots under ZT had nearly 17 and 14% higher total SOC and particulate organic C contents compared with CT (∼9.8 and 3.6 g kg−1 soil) in the 0‐ to 5‐cm soil layer after 9 yr of cropping, despite similar mean aboveground biomass yields of both crops on both CT and ZT plots. Tillage had no effect on C pools in the subsurface layers. Irrigation had positive impact on SOC content in the 0‐ to 5‐ and 5‐ to 15‐cm layers. Although the labile pools of SOC were positively affected by ZT, the recalcitrant pool was not. Plots under ZT and I4 also had higher large and small macroaggregates and macroaggregate‐associated SOC. Thus, adoption of ZT is the better management option for soil C improvement than CT, and irrigation generally enhances the positive impacts. [ABSTRACT FROM AUTHOR]

The identification of suitable crop varieties that respond best to organic management is the key to achieving better crop yields. A field experiment was conducted during the winter season of 2005-2006 and 2006-2007 at Almora (Indian Himalayas) to evaluate the performance of five varieties of garden pea (Pisum sativum L.) and changes in the soil properties under organic and integrated nutrient management (INM) systems. The yield reduction under organic management was 14.4% in 2005-2006 and 10.1% in 2006-2007 compared with INM. Among the garden pea varieties 'Vivek Matar 9', 'Vivek Matar 8' and 'Azad pea 1' produced similar but significantly higher pod yield compared to other varieties. The soil pH, organic carbon, and microbial activities in terms of dehydrogenase and phosphatase (acid and alkaline) were higher in the plots under organic management compared to INM. The latter, however, had higher activity of urease, and N, P, and K contents in soil. We conclude that at least 15-20% price premium for organic garden pea may be required to offset the higher cost of cultivation and low yields under organic production system. Among the garden pea varieties, 'Azad pea 1', 'Vivek Matar 8' and 'Vivek Matar 9' were found suitable for organic cultivation. [ABSTRACT FROM AUTHOR]