ABSTRACT
A field experiment was conducted to investigate the effects of three types of humic acid, i.e. oxidized humic acid (OHA), aminated humic acid (AHA) and microbial-humic acid (MHA), on physico-chemical properties of saline-alkali soil and maize growth. Results showed that the application of all humic acid materials had no significant effect on soil pH in the current season. However, the soil electrical conductivity (EC), the contents of water-soluble Na+ and K+, and sodium adsorption ratio (SAR) decreased under all three treatments of humic acid application measured in up to 40 cm soil depth. OHA had the strongest effect in reducing soil EC, while no significant differences were detected among the three tested materials in reducing contents of water-solu-ble Na+ and K+ and SAR. In addition, humic acid reduced soil NO3--N content and increased soil NH4+-N content, soluble organic nitrogen (SON) content and total soluble nitrogen (TSN) content, with higher effects of AHA and MHA than OHA. Moreover, the application of humic acid materials increased the content of soil available phosphorus, which was most significant in MHA. Humic acid addition could significantly enhance the yield and function leaf SPAD value of maize, which did not vary among the tested humic acid materials. The rank of effect size on apparent utilization efficiency of N and P fertilizer was in the order of AHA>MHA>OHA. While OHA treatment had the highest agronomic efficiency of N and P, AHA treatment achieved the highest partial factor productivity of applied N and P.
Subject(s)
Fertilizers , Humic Substances , Soil/chemistry , Alkalies , NitrogenABSTRACT
We investigated the effects of yam/leguminous crops intercropping on soil chemical and biological properties as well as soil comprehensive fertility in a field experiment. Results showed that compared with the monoculture, both yam/alfalfa and yam/clover intercropping increased the concentrations of nitrate nitrogen (N), available phosphorus (P) and available potassium (K) in the 0-20 cm and 20-40 cm soil layers, while reduced soil pH and electrical conductivity (EC) in early growth period and rhizome rapid expansion period of yam. Intercropping with leguminous crops enhanced the activities of urease, alkaline phosphatase and catalase, and also enhanced soil basal respiration in the 0-20 cm and 20-40 cm soil layers during the whole growth period of yam. There was no influence of intercropping on soil sucrase activity and dehydrogenase activity. The effects of intercropping with leguminous crops on soil fertility at yam harvest were further analyzed by combining the membership function model and principal component analysis. Results showed that intercropping with leguminous crops could significantly increase the soil comprehensive fertility in the 0-20 cm and 20-40 cm soil layers. Therefore, it might be an effective measure to improve soil fertility and environmental quality, as well as alleviate continuous cropping obstacles of yam by yam/leguminous crops intercropping through enhancing soil biological diversity.
