Effects of long-term fertilization on basic soil productivity and nutrient use efficiency in paddy soils

Objectives This paper is to study the effects of long-term fertilization on basic soil productivity (BSP), NPK nutrient use efficiency and their relationship in reddish paddy soil under double-cropping rice system.

Methods A pot experiment based on a long-term fertilizer application was conducted. Three treatments of long-term fertilization were designed including no fertilizer, NPK application and NPK plus rice straws to monitor the impacts of these treatments on yield, BSP (basic soil productivity) yield, BSP contribution rate, NPK absorption rate by rice plants, NPK use efficiency of double-cropping rice, and to analyze the response of NPK use efficiency to BSP contribution rate.

Results The order of BSP yield and BSP contribution rate for the three treatments was: NPKS > NPK > CK. The BSP yield and BSP contribution rate in double-season rice were increased by 113.8% and 93.7%, respectively, in the NPKS comparing to those in the CK and increased by 100.7% and 81.9%, respectively, in the NPK comparing to the CK. At the same fertilizer application rate, NPFP (N partial factor productivity), PPFP (P partial factor productivity), KPFP (K partial factor productivity), SNDR (soil N dependent rate), SPDR (soil P dependent rate), SKDR (soil K dependent rate), NHI (N harvest index), PHI (P harvest index) and KHI (K harvest index) in the NPKS treatment soil were relatively higher comparing to other treatments, whereas NRE (N recovery efficiency), PRE (P recovery efficiency), KRE (K recovery efficiency), NAE (N agronomic efficiency), PAE (P agronomic efficiency), KAE (K agronomic efficiency) and FCR (fertilizer contribution rate) in the NPKS treatment were relatively lower in the three treatments. NRE, PRE, NAE, PAE, KAE, NPE (N physiology efficiency) and KPE (K physiology efficiency) decreased significantly with the increase of BSPCR (contribution rate of basic soil productivity to yield), while NPFP, PPFP, KPFP, SNDR, SPDR, SKDR increased significantly with the increasing of BSPCR.

Conclusions Long-term chemical fertilizers application (NPK), especially long-term chemical fertilizer application combined with rice straw (NPKS) could significantly increase the basic soil productivity. In soils with high basic soil productivity, fertilizer application rate can be reduced under the premise of keeping high or stable crop yield and increasing fertilizer use efficiency.