Impact of nutrient sources on soil carbon pools, soil properties and yield of wheat-urdbean under poplar based agroforestry system
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Date
2020-06
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Field experiment was conducted during rabi and kharif seasons of 2017-19 at Experimental site of Agroforestry Research Centre (old site) near Horticulture Research Centre, Patharchatta of G.B. Pant University of Agriculture and Technology, Pantnagar. The experiment was laid in Randomized Complete Block Design comprising of nine nutrient treatments (chemical fertilizers and its substitution with organics) to study their effects on soil properties under an established poplar agroforestry system with wheat- urd bean cropping sequence. Observed results showed that treatment where application of 50% of recommended dose of N-fertilizers was substituted by FYM+VC gave highest grain yield of wheat (41.6 quintal ha-1) and urdbean (6.86 quintal ha-1) which was significantly higher than all other fertilizer treatments. Due to continuous cropping no perceptible change in pH was observed. Availability of nutrients was found lower in deeper soil layers (15-60 cm) than in surface layer (0-15 cm). The bulk density displayed a growing pattern in respective treatments, with a rise in soil depth (0–30 cm). With integrated nutrient management program, soil physical properties were enhanced. The status of Walkley black carbon showed a growing trend over the years. In control, it was 5.13 g C kg-1, whereas combined use of NPK fertilizers and FYM+VC in 50:50 ratio increased it by 23.5 and 33.2% over T1. With 100 per cent (NPK+FYM+VC) application, the highest
concentrations of various carbon pools were found, whereas the control plot displayed the lowest amounts. Regardless of depths, the optimal application of NPK:FYM+VC in 50:50 on N basis demonstrated a higher concentration of organic carbon pools in the soil relative to both controls taken in the study. All the treatments showed higher accumulation of soil organic carbon fractions in surface soil as compared to sub-surface soil. Growing crops without fertilization reduced the percentages of organic carbon fractions. Active and passive soil organic carbon fractions were at peak with joint application of NPK and FYM at all depths of the soil. Active pool (Cfrac1 and Cfrac2) of soil organic carbon contributed more to total carbon in comparison to contribution of passive pool (Cfrac3 and Cfrac4). The results revealed that incorporation of FYM @ 6 t ha-1 with VC @ 2 t ha-1 and NPK has observed significantly higher soil microbial biomass carbon, TOC stock, C-sequestration and C-sequestration rate than any other management practices. Carbon management index values for different nutrient application schemes were observed and found to be good with INM practices. Carbon budget was significantly positive by use on integrated nutrient application in the two year period rather than only chemical or no fertilization. Maximum increase of 54.6% and 73.5% in dehydrogenase and beta-glucosidase, respectively was recorded in the treatment where 50% of RDF was substituted through FYM+VC after wheat harvest. Also its residual effect on enzymes after urdbean harvest was maximum and increased over open control by 62.3% and 86.1%. Therefore, from this experiment it is concluded that application of NPK in conjunction with FYM and VC could be a sustainable management practice to sustain soil fertility, sequester more carbon and maintain/improve soil health vis-a-vis enhanced production of wheat- urdbean cropping sequence under poplar stands in Mollisols.