Analysis on status of soil potassium and the effects of potassium fertilizer in dryland soil in Guizhou

【Objectives】 Based on soil testing and formulated fertilization in Guizhou, the capacity of supplying potassium in main dry land, in which maize and potato were cultivated for a long term, was explored and the effects of potassium fertilizer were studied as well to provide a scientific reference for high-yield potassium fertilizer management of maize and potato in different producing areas. 【Methods】 The contents of soil readily available potassium and slowly available potassium and the effects of potassium fertilizer were investigated in 106 field test points of maize and 62 points of potato in Guizhou. No fertilizer treatment and treatments of potassium fertilizer and no potassium fertilizer with the same amount of nitrogen and phosphate fertilizer were set to mark out high, medium and low yield areas combined with maize and potato yields in recent three years, then the capacity of supplying potassium was investigated and the effects of potassium fertilizer were studied in the corresponding producing areas fertilized with potassium fertilizer or not. Descriptive statistical analysis, Pearson correlational analysis and stepwise regression analysis methods were employed for data analysis in this paper. 【Results】 The mean contents of soil readily available potassium and slowly available potassium in maize planting region were all lower than in potato planting region. In maize planting region, the soil readily available potassium contents were 155.2 mg/kg (high), 135.1 mg/kg (middle) and 71.0 mg/kg (low) respectively in high, middle and low yield areas, the slowly available potassium contents were respectively 249.5 mg/kg (high), 245.2 mg/kg (high) and 144.3 mg/kg (middle). In potato planting region, contents of soil readily available potassium were 192.6 mg/kg (high), 177.8 mg/kg (high) and 140.3 mg/kg (middle) respectively, and slowly available potassium were 298.6 mg/kg (high), 287.4 mg/kg (high) and 265.5 mg/kg (high) respectively. The relative yields (proportion of no potassium treatment yield to potassium treatment yield with the same amount of nitrogen and phosphate fertilizer) in the two planting regions were all the highest in high yield area, followed by low yield area, middle yield area was the lowest; the yield increase rate and agronomic efficiency of potassium fertilizer followed the sequence of middle yield arealow yield areahigh yield area in maize and potato planting areas, while KPFP (potash partial fertilizer productivity) was high yield area middle yield arealow yield area. There were very significant positive correlations between soil available potassium and slowly available potassium both in maize planting region and potato planting region with the correlation coefficients of 0.635 and 0.550 respectively. The regression model of relative yield, soil readily available potassium and slowly available potassium was at very significant levels.【Conclusions】 The effects of supplying potassium in soil varied greatly between maize and potato planting areas and between different yield areas, the yield-increasing effect of potassium fertilizer in Guizhou was in relation to soil available potassium and potassium supplying potential. Consequently, it was essential to rationally apply potassium fertilizer according to soil potassium content in different planting regions of maize and potato, especially pay more attention to the combined application of organic fertilizer and potassium fertilizer.