Abstract:

To explicit the precision fertilization amount of asparagus lettuce in Yunnan, field experiments of asparagus lettuce were arranged to investigate the relationships between the nutrients data of plough layer, fertilization of current season, and the lettuce yield and net output. It was found that the highest yield of lettuce was obtained by treatment with N2P2K2 in different experiment sites. In different sites, soil nutrients (alkaline hydrolyze nitrogen, available phosphorus and available potassium) and lettuce yield had positive relationships. The Pearson coefficients between lettuce yield of treatment with N, P, K lacking and soil alkali-hydrolyze nitrogen, available phosphorus and available potassium content were 0.91, 0.98 and 0.99, respectively. Soil correction coefficient could reflect the soil fertility potential to some extent. The nutrient critical value for high yield of lettuce in Yunnan was calculated according to optimum fertilizer application rate and the levels of available nutrients in the soil. The regression equations between soil nutrient correlation coefficient and soil nutrient contents could be expressed as follows: y_N=0.123-0.0144lnx_N, y_P=0.2446-0.0474lnx_P, y_K=0.806-0.118lnx_K. The nutrient critical values for high yield of asparagus lettuce could be calculated as follows: N was (286.8±45.6) kg/hm², P₂O₅ was (135.7±4.9) kg/hm², K₂O was (346.3±126.1) kg/hm². The soil nutrient supply capacity was estimated by measuring soil nutrient content before lettuce planting, and the fertilization amount of lettuce in the current season was calculated by subtracting the soil supply from the nutrient critical value for high yield.

Key words: asparagus lettuce, yield, NPK, soil nutrient correlation coefficient, nutrient critical value for high yield