Nutrient release patterns and decomposition characteristics of different crop straws in drylands and paddy fields

To provide theoretical basis for crop straws recycling and straw use in agricultural fields, the characteristics of decomposition and release of nutrients of different crop strawsrice, wheat, corn, rapeseed (green stalk) and broad bean (green stalk) were studied using the nylon net bag method in drylands and paddy fields. The results showed that the decomposition rate of straw was high at the early phase (0-60 d) which then dropped at the later phase (60-360 d). After 360 d, the cumulative decomposition rates of straw were 52.88%-75.80% and 45.01%-62.12% in drylands and paddy fields, respectively. The cumulative decomposition rate of broad bean was significantly lower than that of other crops in the two fields. Furthermore, rapeseed and rice decomposed faster in drylands and paddy fields. At the endpoint of the experiment, the sequence of nutrient release rate of straw in the two fields was K > P > N > C. The rate of carbon release by rice, corn, wheat, rapeseed and broad bean straws was up to 87.37% in dryland and 69.57% in paddy field. The rates of carbon release by rapeseed and rice were significantly higher than those of other crop straws in dryland and paddy field. The average rate of nitrogen release by the five straws tracked the following trend:broad bean (69.72%) > rice (68.45%) > rapeseed (63.60%) > corn (57.28%) > wheat (54.64%) in dryland. The rate of nitrogen release by broad bean was the highest (77.11%) in the paddy field. The rates of release of phosphorus by straw were 89.65%-98.96% and 90.70%-96.80% in dryland and paddy field, respectively. Then the rate of release of phosphorus by wheat was persistently lower than that of any other straw in both fields. The rate of release of potassium by rapeseed was respectively 20.91%, 5.84%, 6.67% and 5.19% higher than that of wheat, rice, corn and broad bean in dryland. Also the rate of release of potassium by wheat was significantly lower than the others. Overall, the decomposition and nutrient release rates in dryland were higher than those in paddy field. Rapeseed green straw in dryland, and rice and maize straws in paddy field were more easily decomposed than other crops straws. The release rate of potassium was highest in all the tested elements.