Most of the arid and semi-arid areas in China is characterized in low temperature and insufficient soil moisture, resulting in a low decomposition rate of crop straw. Consequently, crop straw is not returned to the field after harvest, because the crop residue in topsoil blocks the tilling and sowing machine, and sometimes prevents the seeds from germination. Thus, an innovative method of returning straws in the soil is needed to solve the above problems. In this study, high density organic matter (HDOM) was made of wheat straw (HDOM-W) by granulator, with addition of 10% biochar (HDOM-WB) and 10% elemental sulfur (HDOM-WS) in weight, respectively. The relationship between hardness of HDOM and soil moisture, the effect of HDOM on wheat germination rate, the decomposition characteristics and the effect of HDOM on wheat growth were systematically assessed. The results showed that the hardness of HDOM-W decreased sharply when the soil moisture content increased to 3%. Compared to chopped wheat straw (CWS) treatment, wheat germination rate was not significantly reduced by HDOM-W. Lower decomposition rates were found in HDOM-W, but the trends were similar. The biomass, total N and P concentration of wheat in HDOM-WS increased by 137.9%, 137.1%, and 141.8%, respectively (P< 0.05) compared to CWS. Wheat K concentration in HDOM-WB increased by 39.7% (P< 0.05). Therefore, application of HDOM in soils can improve seed bed, promote crop growth and increase nutrients, which finally elevating soil fertility. Organic byproducts like crop straws, fruit tree branches, grasses, abandoned wood furniture, etc. can be potentially recycled as HDOM and returned to the field to tackle the problem of organic waste disposal and sustainably maintain soil quality.

high density organic matter, granular wheat straw, hardness, germination rate, decomposition