Impacts of biochar and phosphorus application on soil phosphorus availability and soybean phosphorus uptake

Abstract

Biochar is beneficial to soil phosphorus (P) availability and crop growth, but the effects vary greatly across different soil types. We investigated the effects of rice straw biochar (4% of total mass) and P application (0, 30, and 90 kg P·hm-2) on soil P availability, phosphomonoesterase activity, and soybean P uptake by using lateritic red soil (pH 4.91) and cinnamon soil (pH 7.24) as test materials. The results showed that biochar application at different P levels significantly increased available P and total P in both soils. Biochar application with 30 kg P·hm-2 increased soil available P with maxima at 192.6% and 237.1% in lateritic red soil and cinnamon soil, respectively. Biochar application with 30 kg P·hm-2 in lateritic red soil significantly increased the activity of alkaline phosphomonoesterase by 78.9%, decreased the content of active organic P by 39.3%, and subsequently stimulated soybean P absorption and growth. Biochar amendment significantly reduced active organic P content in cinnamon soil, but did not affect soil phosphomonoesterase activity and plant growth. The content of active organic P was significantly negatively correlated with soil available P content. In summary, the effect of biochar on soil P availability varied across different soil types (lateritic red soil > cinnamon soil) and P levels (better at 30 kg P·hm-2). Our results could provide scientific basis for a promising application of biochar in reducing the amount of P fertilizer and increasing soybean P uptake, especially in lateritic red soil.