Effects of application of phosphorus and potassium fertilizers on ion compositions of soil solution in solar greenhouse

An incubation method was used to study the effects of application of phosphorus (P) and potassium (K) fertilizers on the electric conductivity (EC) and ion compositions in soil solution under sunlight greenhouse. The EC and concentrations of K+, Na+, Ca2+, Mg2+, NO3- ions and mole ratios of K+ / Ca2+, K+ / Mg2+ in soil solution of greenhouse without addition of fertilizer were 2.5, 95.0, 16.6, 1.9, 3.2, 4.0, 31.0 and 39.0 times of that in arable soil, respectively, indicating the serious accumulation and imbalances of ions in greenhouse soil. The application of P and K fertilizers had different effects on ion composition of soil solution. Addition of P fertilizer significantly decreased the EC and concentrations of Ca2+, Mg2+ ions both in arable and greenhouse soils, its effect on concentrations of K+, NO3--N and NH4+-N ions in the soils was not significant. As the increasing addition of K fertilizer, the EC and concentrations of K+, Na+, Ca2+, Mg2+ ions and mole ratios of K+/Ca2+, K+/Mg2+ in solutions of arable and greenhouse soils increased. The study indicated that the effects of inadequate application of P and K fertilizer on the over accumulation of salts and cation imbalances deserve further study.