Effects of chemical fertilizer and slow-release compound fertilizer on surface electrochemical properties in neutral and slight alkaline soils

Abstract: Soil surface electrochemical properties can reflect the characterization of fertilizer preserving and supplying, and further reveal soil fertility. Researching on the effects of slow/controlled release fertilizers on the soil surface electrochemical properties can uncover the essences of improving soil fertility and promoting the crop growth. In this research, two experiments were carried out: In the first experiment, neutral and slight alkaline soil were cultured 90 days at 25 ℃ indoor, with 6 treatments designed as no fertilization (CK), chemical fertilizer (CF), common compound fertilizer (CCF), slow-release compound fertilizer with different levels (SRF1, SRF2 and SRF3). The application rate of nitrogen, phosphorus, potassium in SRF1, SRF2 and SRF3 treatments were respectively 200, 120, 120 mg/kg, 400, 240, 240 mg/kg and 800, 480, 480 mg/kg, and the fertilizer application rate of CF and CCF was same as SRF1. Soil surface electrochemistry properties, such as surface potential, surface charge density, specific surface area and surface charge number, were investigated, and the correlations between physical-chemical properties and surface electrochemical properties of soil were also studied. To ensure the accuracy of the investigation, field experiment was conducted to study the effects of chemical fertilizer (CF), common compound fertilizer (CCF) and slow-release compound fertilizer (SRF) on soil surface electrochemical properties and the yield of eggplants in neutral and slight alkaline soils. The application rate of nitrogen, phosphorus, potassium of different fertilizer treatments were 350, 200 and 200 kg/hm2 in field experiment. The results showed that SRF1 treatment increased the neutral soil surface potential, surface charge density, surface charge number compared to CF in the first experiment under the constant temperature incubation condition. Comparing with CK, soil specific surface area of all fertilizer treatments were significantly (P<0.05) increased by 34.2%-81.2%. Moreover, the surface charge density and specific surface area of neutral soil had an increasing trend with increasing of the application rate of slow-release compound fertilizer. In addition, the correlation analysis showed that soil surface charge density and specific surface area were positively correlated with soil pH value and organic matter. In the field experiment, the effect of slow-release compound fertilizer on neutral soil surface potential, surface charge density and surface charge number was greater than that of chemical fertilizer. The slight alkaline soil surface charge number in SRF treatment was significantly higher than that of chemical fertilizer and common compound fertilizer. Compared to CF and CCF, the slight alkaline soil surface charge density, the SRF treatment was significantly increased by 7.9% and 6.5% in soil planted Heisheng eggplant and 12.9% and 5.3% in soil planted Zhuqie. The correlation analysis showed that there was a significant (P<0.05) or extremely significant (P<0.01) correlations between soil surface electrochemical properties and the yield of eggplants. In conclusion, slow-release compound fertilizer with appropriate content and proportion, which constantly released a variety of forms of nitrogen and organic matter, was the material basis to stabilize soil surface electrochemical properties, improve the characteristics of keeping soil fertility, so nutrient substances could be continuously supplied in a long period for the growth of crop.