Importance of adding woodchips to local amendments for improving soil health and increasing yield in severely degraded soils of Northern China

Wood chips, together with crop straw and manure, were demonstrated as feasible amendments for improving overall soil health and enhancing plant growth in severely desertified areas in Northern China in our previous studies. However, the effects of their mixtures are unclear. In this study, we evaluated the effect of three different amendment materials, when used alone and in combination, on physical, chemical, and biological properties of desertified soil and on the associated growth of alfalfa in Ningxia, Northern China. Four replicate microcosms were set up containing sandy soil mixed with 3% (w/w) of each of the following treatments: cow manure (CM), corn straw (CS), and poplar branches (PB) and their mixtures CS-PB, CM-PB, CM-CS, and CM-CS-PB. Measurements were conducted 7 and 15 months after the start of the experiment. Results showed, as a whole, treatment CS-PB improved soil physical properties more than other amendments during the whole experimental period, compared with control. However, the best establishment of alfalfa in the first year and best growth in the second year occurred in the CM-CS-PB treatment. Moreover, available N and urease were the most important driving factors affecting alfalfa growth during the whole experimental period, as shown by redundancy analysis. However, interestingly, the CM-CS-PB also functioned better in maintaining N supply and accelerating microbial activity than the other amendments. Therefore, we concluded that wood chips have a unique advantage in improving overall soil health and alfalfa growth when combined with straw and manure as new amendments.