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20111
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Subject: Soil Science × Author: Abha Mundepi × End date: 2013 × Start date: 2011 × Type: Thesis ×
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    ThesisItemOpen Access
    Impact of inorganic fertilizers and organic matter recycling on soil organic carbon pools in rice-wheat system
    (Punjab Agricultural University, Ludhiana, 2011) Abha Mundepi
    The influence of long-term application of FYM, green manure and wheat straw on soil properties and soil organic C pools was studied after 27 cycles of rice-wheat cropping on a sandy loam soil at the research farm of P.A.U, Ludhiana. Each of the organic source viz. FYM, wheat straw and green manure was applied at two rates to supply 25 and 50% of the recommended N dose to rice. The application of organic amendments significantly lowered soil pH, electrical conductivity, bulk density and increased water holding capacity, water stable aggregates and mean weight diameter. Compared to unfertilized control application of organic manures and wheat straw significantly enhanced total C (26-35%), Walkley and Black soil organic C (22-28%), particulate organic C (48-65%), KMnO4-oxidizable C (11-47%), hot water soluble C (25-50%) and microbial biomass C (46-67%). When compared across all treatments, concentration of different pools of organic C was lower in 15-30 cm depth than 0-15 cm depth. The easily oxidizable organic C fractions, Cfrac1 and Cfrac2, together constituted about 67% of the total organic C. The other two less labile fractions accounted for only 33% of the total C. Application of organic amendments in conjunction with mineral fertilizers significantly increased the content of light fraction and heavy fraction organic matter. Heavy fraction C constituted about 64-82% of total C whereas light fraction C accounted for only 7-13% of total C. Application of wheat straw resulted in a greater (34%) increase in mineralizable C compared (25-29%) with FYM and green manure addition. The C and N density was higher in macroaggregates than microaggregates. Application of organic sources increased total N (42-72%), light fraction N (30-115%) and heavy fraction N (34-69%) compared to control. The use of recommended + sub-optimal rates of inorganic fertilizers did not influence soil properties and various organic C pools significantly. The study emphasized the importance of conjoined use of organic amendments along with inorganic fertilizers for maintaining soil fertility and increasing C sequestration in soil that can help in mitigating CO2 emissions.