ABSTRACT
Sustainable nutrient management practices have the potential to enhance carbon (C) storage capacity of agricultural soils that may help offset increasing atmospheric CO2 concentration. Nutrient management practices on long-term basis differentially influence aggregates and distribution of soil organic C (SOC) present within aggregates, which in time may affect C stabilization. The present study assessed the impact of long-term application of fertilizers for 44 years either alone or integration with farmyard manure (FYM) on bulk density, SOC and C pools, potassium permanganate oxidizable C (KMnO4), aggregate stability and distribution of C fractions within different size aggregate under maize-wheat cropping sequence. The application of 100%NPK+FYM significantly (P< 0.05) improved soil aggregation and mean weight diameter (MWD). The percent of macro-aggregates (MacroA) and meso-aggregates (MesoA) was maximum in 100%NPK+FYM followed by NPK and the minimum in the control treatment. Irrespective of aggregate classes, TOC (g kg-1 aggregate) was maximum in 100%NPK+FYM treatment with an average of 8.42 g kg-1 aggregate as compared to control (5.05 g kg-1 aggregate). If averaged across the treatments, TOC concentration in aggregates followed the order MacroA> MesoA>MicroA. Correspondingly, results for KMnO4-C were similar in different treatments and aggregate classes. Application of FYM with inorganic fertilizers (NPK) or NPK showed a significant increase in all oxidizable organic C fractions particularly recalcitrant C fraction, which reflects the stable nature of OC as compared to very labile and labile C fractions. In general, C present in mineral fraction and large-sized aggregates (MacroA) has higher recalcitrant fractions of SOC as compared to small-sized aggregates (MesoF and MicroF). The study concluded that long-term balanced and integrated nutrient management improved soil aggregation, C distribution within aggregates, and C storage capacity of soils under maize-wheat. Carbon associated with macro aggregate and a mineral fraction has more recalcitrant C fraction compared to meso and micro aggregate fractions.
ABSTRACT
A field experiment was conducted for two years to find out best water management practice to mitigate methane emission from the rice-fields. Continuously flooded conditions yielded two major flushes of methane emission and on an average resulted in relatively higher rate of methane emission (2.20 and 1.30 mg m-2 hr-1, respectively in 2005 and 2006) during the kharif season. The methane flux was reduced to half (1.02 and 0.47 mg m-2 hr-1, respectively in 2005 and 2006) when rice fields were irrigated 2-3 days after infiltration of flood water into the soil. Irrigating the field at 0.15 bar matric potential reduced seasonal methane flux by 60% (0.99 and 0.41 mg m-2 hr-1, respectively in 2005 and 2006) as compared to completely flooded conditions, without any decline in grain yield (60 q ha-1).
ABSTRACT
A field experiment was conducted for two years on a sandy loam (Typic Ustochrept) soil of Punjab to study the effect of organic materials and rice cultivars on methane emission from rice fields. The methane flux varied between 0.04 and 0.93 mg m-2 hr-1 in bare soil and transplanting of rice crop doubled the methane flux (0.07 to 2.06 mg m-2 hr-1). Among rice cultivars, significantly (p < 0.05) higher amount of methane was emitted from Pusa 44 compared to PR 118 and PR 111. Application of organic materials enhanced methane emission from rice fields and resulted in increased soil organic carbon content. The greatest seasonal methane flux was observed in wheat straw amended plots (229.6 kg ha-1) followed by farmyard manure (111.6 kg ha-1), green manure (85.4 kg ha-1) and the least from rice straw compost amended plots (36.9 kg ha-1) as compared to control (21.5 kg ha-1). The differential effect of organic materials in enhancing methane flux was related to total carbon or C:N ratio of the material. The results showed that incorporation of humified organic matter such as rice straw compost could minimize methane emission from rice fields with co-benefits of increased soil fertility and crop productivity.