Soil Bio-Chemical Properties Influenced By Biochar and Manure Application.

A field experiment was conducted to evaluate the effects of biochar and manure application to a Warden Silt loam soil on bio-chemical properties under maize crop. Treatments included: (i) annual application of 336, 50,  and 140 kg/ha N, P, and K, respectively (NPK); (ii) NPK + 10 Mg ha^-1 biochar (BC+NPK); (iii) 10 Mg ha^-1 biochar plus 168000 l ha^-1 dairy manure effluent (BC+DE); (iv) only DE, equivalent to 336 and 64 kg/ha N, and P, respectively. The experiment was conducted using a randomized block design with three replications. Soil samples were collected in the fall 2012 (after 3 years crop cycle) and analyzed for the following parameters. At 0-15 cm depths, soil pH (1:2) values were 7.28, 7.50, 8.08, and 8.2 for NPK, DE, BC+DE, BC+NPK treatments respectively.  Total organic carbon (TOC) increased by 60% and 98% for the BC+NPK, and BC+DE treatments, respectively.  Microbial biomass (MBC) decreased in the order: (BC+NPK) > (BC+DE) > NPK > DE treatments.  In BC+NPK treatment MBC was found to be 743 µg/g of soil in 0-15 cm depth. Fluorescein di-acetate (FDA) hydrolysis activity was also stimulated by biochar application similar to the trend observed for MBC. There were significant correlations among the above response parameters, with the highest correlation coefficient (R² = 0.80***) between pH and MBC. This study demonstrated an increase in MBC and FDA activity associated to biochar application, which appears to have been induced by the direct effects of biochar on soil pH and TOC.