Application of Systematic Variation Method for Optimizing Mineral Nutrition of Soilless‐Grown Zucchini Squash

Abstract

Zucchini plants (Cucurbita pepo L.) were grown in perlite bags under greenhouse conditions in 2000 and 2001 at Viterbo Experimental Farm, Central Italy. In a 2000 greenhouse experiment, treatments were six formulations with different ratios of NO3 −, SO4 2−, PO4 3−, K+, Ca2+, and Mg2+ × two total nutrient levels (0.5 and 1 eq plant−1). An unfertilized treatment was also tested. Each nutrient ratio treatment was defined by a high proportion of one nutrient and a low proportion of other ions of equal charge with the same anion:cation ratio and total concentration. The 2000 data of fruit yield and total dry weight biomass were used to calibrate the mathematical model (according to the systematic variation method) relating fruit yield and total dry weight biomass to nutrient proportions and total nutrient levels of the fertilizer and total nutrition. For both fruit yield and total plant biomass, the optimal proportions of macronutrients in the fertilizer and total nutrition were largely composed by NO3 −, K+, Ca2+, and Mg2+ (average 82% of total macronutrients), while the mean optimal total concentration was 2.89 eq plant−1. A verification of the calibrated model against 2001 experimental data showed that the model was able to predict fruit yield and total plant biomass by varying nutrient composition of the medium.