Farrag , D. Kh.; R. Kh. Darwesh* and E. A. Moursi ( 2015). The combined effect between irrigation and k-fertilizer forms on squash productivity in the north Nile delta regionBull. Fac . Agric., Cairo Univ., 66:1-16
Abstract: The current experiment was carried out in a clay soil at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate, Egypt during the two seasons of 2013 and 2014 to study the effect of irrigation and potassium fertilizer forms on squash productivity and some water relations. Four irrigation treatments: traditional irrigation (I0), irrigation according to class A pan evaporation (I1), irrigation according to Hargreaves equation 1981, (I2) and irrigation according to Ibrahim equation 1980, (I3) were tested. Five K-fertilizer forms;100% potassium mineral fertilizer (K1), 75% potassium mineral fertilizer and 25% rock feldspar (K2), 50% potassium mineral fertilizer and 50% rock feldspar (K3), 25% potassium mineral fertilizer and 75% rock feldspar (K4) and 100% rock feldspar (K5) were tested. The important findings could be summarized as follows:
1- The highest overall mean values of water applied (IW) and water consumptive use (CU) were recorded under the control treatment (irrigation without any stress during the growing season, treatment, I0) where the values were 48.89 cm (2053.5 m3fed-1) and 42.44 cm for WI and CU, respectively, but consumptive use efficiency (Ecu, %) recorded under I1 had a mean value 93.44%. Irrigation with I1, I2 and I3 saved irrigation water by 12.05, 20.59 and 16.75 % for IW. The linear regression equations between irrigation water applied and K-fertilizers forms proved that the relation between IW and CU was more reliable in the two seasons.
2- Productivity of irrigation water (PIW kgm-3) on fresh yield basis increased with more frequent irrigation application, while water productivity (WP kgm-3) was the highest under I2 with overall mean value of 12.35 kgm-3.
3- Vegetative parameters (shoots and dry weight, plant height, number of leaves per plant and leaf area) were significant for both irrigation and K-forms, as the interaction between I and K had significant effect, except plant height and the number leaves per plant in the second season which were non-significant. Increasing irrigation applied increased all vegetative growth parameters.
4- Results also showed that irrigation water applied and K-fertilization forms had significant effects on yield and its quality. The best combination of treatments was I0*K3 with 149.5 and 160.0 g, for weight of fruit, 5.90 and 6.28 ton fed-1 for total yield, 22.65 and 23.55 ton fed-1, 5.58 and 5.90 ton fed-1 for early yield, 15.20 and 15.60 mg100g-1 fresh weight for vitamin C and 4.92 and 4.67 % for TSS in the first and second seasons, respectively.
5- The values of N P K and chlorophyll content in the leaves were significantly affected by I and K. Also, the interaction between I*K showed highly significant effect on the above mentioned studied parameters.
Keywords: (Squash, water applied, K-fertilizer forms, consumptive use, water productivity.)
