Evolution of cinnamon soil productivity and the main influencing factors under long-term fertilization

Objectives Soil productivity is one of the key factors affecting the sustainable development of agriculture. The study examined the effect of non-fertilizer and organic fertilizer combined with chemical fertilizer (conventional fertilization) on cinnamon soil productivity, and the aim was to provide theoretical basis for the improvement of fertilization and productivity of cinnamon soil.

Methods The research was based on the 28 long-term experiments of cinnamon soils located in Beijing, Hebei, Shanxi, Liaoning, Shandong, Henan and Shannxi. The organic matter, total nitrogen, available P and available K contents were measured in the soils from the treatments of blank control and conventional fertilization from 1988 to 2016. The yield variation of maize and wheat with the experimental years were investigated. The productivity evolution of cinnamon soil was analyzed, and the key factors of soil fertility and fertilization factors that governed crop yield were elucidated by principal component analysis (PCA).

Results 1) Both the yields of wheat and corn in blank control fields decreased firstly and then increased slowly, and the average yields were 3175 and 4056 kg/hm², respectively. The wheat yields in conventional fertilization fields increased gradually and the average was 6124 kg/hm²; the corn yields tended to be stable and the average was 7432 kg/hm². The degree of increase for the wheat and corn yields firstly increased and then decreased, with the mean increase of 2901 and 3429 kg/hm², respectively. The sustainable yield indices (SYI) of wheat and corn were 0.57 and 0.54 under fertilization treatments, which were 54.82% and 52.49% higher than those in CK. The coefficients of variation (CV) of wheat and corn yields were decreased by 44.70% and 40.77%, respectively. 2) The contribution rates of soil natural fertility of wheat and corn season were 53.0% and 54.2% for the fertilization treatment compared to the non-fertilization treatment respectively, and the CV were 41.2% and 37.6%, respectively. The fertilizer agronomic efficiency of wheat increased firstly and then decreased with a mean value of 6.36 kg/kg, while that of corn decreased firstly and then stabilized with a mean value of 13.89 kg/kg. The agronomic efficiency of nitrogen fertilizer decreased with fertilization years. 3) There were five principal components affecting wheat yield and the cumulative contribution was 71.729%; and there were four principal components affecting maize yield with the cumulative contribution of 67.948%. For the two crops, the rate of organic manure was the most important factor, followed by soil total nitrogen and organic matter content.

Conclusion The productivity of cinnamon soil is affected by the rate of organic manure, the contents of soil total nitrogen and organic matter. Therefore, the increase of productivity of cinnamon soil area is significantly influenced by the improvement of soil fertility and the reasonable application of fertilizer. In order to improve soil fertility, it is suggested that straw should be returned to the field, organic fertilizer be applied, the proportion of phosphorus fertilizer be increased appropriately, the proportion of nitrogen fertilizer be reduced, and the proportion of organic fertilizer be increased.