Effects of different fertilization treatments on forage yield and soil properties in sudangrass–ryegrass rotation

Sudangrass and ryegrass rotation was adopted and developed as a new cultivation technique in many pisciculture regions in south China. Because cultivated soil had low pH, poor soil fertility and extensive cultivation with poor soil management, forage yield was insufficient and hindered the development of the productive forces in forage-fish system. A pot experiment was carried out in Hubei Province, central area of China and the objective was to determine the effects of soil amendments including fertilizers (NPK), lime and organic matter (OM) application on forage yield and soil properties in sudangrass-ryegrass rotation. The results showed that the application of soil amendments increased forage yield significantly. In the whole rotation, forage yield in NPK, NPK+Lime, and NPK+OM were 6.1, 6.8 and 7.3 times higher than that in the control (CK), respectively. Based on NPK treatment, the application of lime and OM increased yield by 9.5% and 17.2%. Nutrients uptake results demonstrated that different fertilization treatments significantly increased N, P, K content of forages and promoted nutrient uptakes. N, P and K uptake amounts of sudangrass and ryegrass in NPK treatment increased by 6.3 times, 7.7 times and 7.0 times, respectively, when compared with that in CK, and NPK+Lime treatment increased by 6.5 times, 8.6 times and 7.4 times, and NPK+OM treatment increased by 6.2 times, 9.2 times and 7.4 times, respectively. The soil analysis results showed that the application of lime and OM increased pH value in the acidic soil compared with that of CK and NPK treatments after the experiment. Based on NPK treatment, lime application increased soil available Ca by 20.7%, and decreased soil available Fe and Mn by 26.5% and 41.2%, respectively. Based on NPK treatment, OM application improved soil available N, P and K content significantly.