Long-term application of organic manures and chemical fertilizers improve the organic carbon and microbiological properties of soil under pearl millet-wheat cropping system in North-Western India

An on-going long term field experiment started in Rabi 1995 at the Research Farm of the Department of Soil Science, Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana (India) under the pearl millet-wheat cropping system was selected to study the effect of long-term application of organic manures and fertilizers on soil organic carbon and microbiological properties. Highest soil organic carbon (SOC: 1.18 %), dissolved OC (DOC: 64.74 mg kg(-1)) content, microbial biomass C (MBC: 618.40 mg kg(-1)), dehydrogenase (DHA: 72.83 mu g TPF g-1 24 hr(-1)), alkaline phosphatase (APA: 685.44 mu g PNP g(-1) soil hr(-1)) and aryl sulfatase (ASA: 12.56 mu g PNP g(-1) soil hr(-1)) activities were observed with the application of 15 Mg FYM+150 kg N+30 kg P2O5 ha(-1). Integrated application of chemical fertilizers with pressmud showed superiority in the improvement of microbial biomass nitrogen (MBN: 73.73 mg kg-1) and urease activity (69.54 mu g NH(4)(+ )g(-1) hr-1) than FYM or poultry manure plus NP. Beneficial impacts of the sole application of organic manures on SOC, DOC, MBC content, DHA, APA, and ASA were found in order as: FYM > pressmud > poultry manure. Impacts of nutrient management practices on soil carbon fractions decreased with depth. Poultry manure application, either alone or in combination with NP fertilizers was inferior to FYM and pressmud. The SOC had a positive relationship with MBC (R-2 = 0.95) and MBN (R-2 = 0.75) and, also showed a highly positive and significant correlation with microbiological properties of soil. This dynamic equilibrium among soil properties indicated that the nutrient management practices that improve SOC could lead to improve soil fertility and accrued microbiological properties in these soils. This study revealed that conjuctive use of organic manures and chemical fertilizers have positive impact on soil fertility and microbiological properties as compared to sole application of organic manures or fertilizers; and among organic manures, FYM was superior to pressmud followed by poultry manure.