Effects of Nitrogen, Phosphorus and Potassium Fertilizer on Yield an dQuality of Asparagus (Asparagus officinalis)

Abstract

The effects of NPK on quality and yield of asparagus grown on Korat gray mottled soil (fine - loamy, siliceous, isohyperthermic, Aquic Oxic Paleustults) was investigated as Sisaket Horticultural Research Centre from 1987 to 1989. Three replications of 20, 30 and 40 kg/rai/year of N, P2O2 and K2O in 3 x 3 x 3 treatment combinations plus a check treatment were used to perform this RCB experiment. The yield from fertilized treatments averaged 73, 129 and 144 percent hight than the check respectively from the first to third year. No yield differences were obtained among these treatments in the first year but yield responding to nitrogen and phosphorus were difinite (p<0.05) in the second and thired year with positive interaction between the two sources, N to P2O2 ratio fo 1 : 1 at 30 kg/rai produced the optimum annual and combined yields of 704 kg in second year and 749 kg in third year which combined to 2,718 kg/rai. This was not found in any responsive to potassium. Spear quality did not differ under various fertilizer combinations. Increasing in nitrogen and potassium fertilizer rates slightly increased in fiber content but total soluble solid (sugar content) of all fertilizer treatments was normal. Fertilizer application produced an overall greater number of larger spear than the check treatment. The effect is attributed more to phosphorus than the nitrogen or potassium fertilizer sources.