Effects of different stable organic matters on physicochemical properties of lime concretion black soil and maize yield

With poor physical properties and low organic matter content, lime concretion black soil is one of the lowest productive soils and is widely distributed in the Huang-Huai-Hai Plain in China. Although the physical and chemical properties of lime concretion black soil influenced by exogenous organic matter have been widely reported, few studies have focused on the effects of synchronous application of organic materials with different stabilities in lime concretion black soil. Thus a two-year pot experiment was conducted at the State Experimental Station of Agro-Ecosystem in Fengqiu to evaluate the effects of organic materials with different stabilities (biochar, organic fertilizer and straw) on the physico-chemical properties of lime concretion black soil and maize yield. Eight treatments were designed based on applications of different organic materials with the same inputs of carbon and nitrogen, which were CK (no fertilizer), straw (S), organic manure (M), biochar (C), 1/2 straw + 1/2 organic manure (SM), 1/2 biochar + 1/2 straw (CS), 1/2 biochar + 1/2 organic manure (CM), and 1/3 biochar + 1/3 organic fertilizer + 1/3 straw (CSM). Compared with CK, the application of different organic materials decreased soil bulk density by 19.60%32.23% and increased saturated soil moisture, field capacity and total porosity by 7.91%28.99%, 10.47%30.76% and 10.36%28.21%, respectively. There were significant differences in total organic matter and labile organic matter contents of soil between CK and organic materials application treatments. The trends of increase in different components of organic matter were similar. On the other hand, the variation range of high labile organic matter was obviously greater than that of total organic matter. The high labile organic matter content increased by 39.22%8.83%, whereas that of total organic matter increased by 11.00%37.00% under organic materials treatments. Bulk density of CSM (1.28 gcm^-1) was lower than those of C (1.30 gcm^-1) and S (1.36 gcm^-1). Total porosity of CSM was highest (58.53%) among all treatments. Total porosity under CS, SM, S, C and M treatments was 56.90%, 54.38%, 55.62%, 53.18% and 50.38%, respectively. Total organic matter content of CS, CM, CSM, C and S was 30.76 gkg^-1, 32.99 gkg^-1, 31.45 gkg^-1, 25.36 gkg^-1 and 26.16 gkg^-1, respectively. Maize yield for different treatments were similar in trend to that of total organic matter content. Grain yield for CS, SM and CSM was respectively 463.67 gpot^-1, 376.31 gpot^-1 and 471.77 gpot^-1; higher than that of C, S and M. Overall, mixed application of biochar, straw and organic fertilizer was by far better than the application of sole organic material in terms of improving soil physico-chemical properties and maize yield.