Pumpkin Yield Affected by Soil Nutrients and the Interactions of Nitrogen, Phosphorus, and Potassium Fertilizers

To study the effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizers on the yield of 'Jianbao' pumpkin (Cucurbita maxima Duch), we conducted experiments using the "3414'' optimal design scheme in Dehua County, Quanzhou, Fujian, China. Overall, three fertilizer factors (N, P, K) were tested with four fertilization levels (level 0, no fertilizer; level 1, 0.5-times the typical fertilizing amount; level 2, typical fertilizer application; level 3, 1.5-times the typical application), with a total of 14 different fertilization treatments. Based on the results of this study, a corresponding fertilization performance model was established to provide a practical basis for ensuring highly efficient cultivation of pumpkin in the field. Our results showed that the experimental data could not be fitted with a ternary quadratic polynomial fertilizer model, but that it could be fitted with a single-variable quadratic fertilizer model. According to the fitted model, pumpkin yield first increased and then decreased with the increasing amount of N, P, and K used. We identified significant regression relationships between 'Jianbao' pumpkin yield and the amount of N, P, and Kin the fertilizer. Finally, based on the single-variable quadratic fertilizer model, we suggest that the quantities of N, P, and K fertilizer used for growing 1 ha of 'Jianbao' pumpkin should be 390.5, 213.8, and 371.3 kg, respectively.