Effect of biochar and organic manures on soil physicochemical properties
Our results showed an increase in soil moisture, macro aggregate stability,MWD, and IR and reduction in BD and PR with soilamendments addition in one season at surface soil. However, there were no significant impact of biochar and manures on soil physical properties at subsurface soil depth. Increase in soil moisture, macro aggregate stability, and IR by 9.2%, 3.1%, 20.8%, respectively, in biochar addition treatments than no biochar (B0) might be due to porous nature, high surface area and aromatic nature of biochar that resulted in improved soil aggregation, soil water retention and water use efficiency12–14. The increase in macro aggregate stability and MWD in case of biochar treated plots probably is due to the contribution of organic carbon present in biochar. Biochar promotes growth of soil microorganisms which secretes polysaccharides that increases adherence of soil colloidal particles.According to our results it is evident that WUE was higher (13.6%) in biochar applied plots than B0(Table 6). These findings are in agreement with Abrol et al.15 who reported that biochar provide favourable soil physical condition for soil water movement. Reduction in BD and PR with biochar amended plots further supports the results obtained by many researchers Laird et al.16, Mukherjee and Lal17 and Gwenzi et al.18 as high porosity of biochar and highly stable carbon of biochar resulted in increased pore volume and decreased soil compaction.
Similarly, manure incorporation showed significant improved soil physical properties over control. Reduction in bulk density and penetration resistance and increased moisture percent, aggregation, infiltration rate and water use efficiency was observed with manure addition. Comparable results were observed by Saddiq and Al-Ameer19 who found reduction in soil bulk density due to the formation of stable aggregates with organic matter incorporation into the soil.2.3–2.5 times, increase in WUE was noticed with manure addition might be due to the increase in photosynthesis and reduction in transpiration losses of crop, which leads to increase in crop yield20. Similarly, Sarkar et al.21 observed that addition of organic manures to soil enhanced the moisture retention capacity of soil. Manure positively modified the soil structure and increased soil water and nutrient retention capacity of soil22–23.
Biochar treated plots showed the maximum soil pH. This might be due to alkaline nature of biochar, high surface area and porous nature of biochar that increased cation exchange capacity of soil24. Similar results of increase in EC were also found by Pandian et al.25; Raison26 who revealed that the increase in EC because of incorporation of biochar are generally due to carbonates of alkali, amounts of silica, phosphates and small amounts of organic and inorganic nitrogen. Similar results of increase in EC were also reported by Dutta et al.27 who reported the increase in EC of soil due to application of vermicompost were generally due to chloride and sulphate salt.
Results revealed that short term effect of biochar and manure can enhance C stability in macro aggregates this could be due to carbon released from the decomposition of organic manures is sequestered by the biochar. Joseph et al.28 also reported less mineralization resulted in physical, enzymatic and microbial degradation of aggregate associated C. Earlier research showed biochar is carbon rich recalcitrant material however it improved labile carbon by improving soil structural cohesion between particles 29–30.
Effect of biochar and organic manures on crop performance and economics
Besides containing labile and recalcitrant carbon biochar adds some other nutrients into soil (P, K, H and S). Incorporation of biochar with manures further accelerates the nutrients availability and reduced the nutrients leaching and fast decomposition of manure as reported by Adekiya et al.5 and Manolikaki, I.& Diamadopoulos, E31. Maximum root length in biochar and OM3 treatments was found due to reduction in bulk density, penetration resistance and elevated aggregate stability of soil. Adekiya et al.5 reported similar findings. Similarly, biochar and organic manures both individually and in combination decreased forking percentage in radish because of improved physical condition of soil, treated with biochar as well as organic manures. These amendments make soil suitable for even root penetration and growth inside the soil. Similar results were found by Subedi et al.32.
Incorporation of biochar and manures (FYM + VC) gave highest net returns (Rs138325) and lowest (37450) was observed in control which might be due to the high radish yield and root length. Similarly, results showed that biochar application at the rate of 3 t ha− 1with FYM and VC (OM3B) was superior with B:C ratio of 1.5 while the lowest B:C ratio (1.0) was recorded in control(OM0B0)33.