INFLUENCE OF IRRIGATION LEVELS, ANTITRANSPIRANTS AND POTASSIUM SILICATE ON GROWTH, FRUIT YIELD AND QUALITY OF SWEET PEPPER PLANTS (Capsicum annuum L.) GROWN UNDER DRIP IRRIGATION

Abstract

Two field experiments were conducted at a private farm near EL-Mansoura city, El-Dakahlia Governorate, Egypt, during the two successive seasons of 2011 and 2012 to study the effect of three water irrigation levels, the first was 2600 m3 fed-1 as the control treatment (the traditional irrigation amount used by the farmers in the area), the 2nd and the 3rd treatments were 1800 and 1000 m3 fed-1, respectively, as deficit irrigation treatments as well as four foliar applications, i.e., control, magnesium carbonate, kaolin and potassium silicate on growth, chemical composition, yield, water use efficiency and fruit quality of sweet pepper plants (Gedeon F1 Hybrid) cultivated under drip irrigation system in clay-loam soil at northern of Nile Delta lands. The main results could be summarized as follows: - Applying the high irrigation water level (2600 m3 fed-1) or the deficit level (1800 m3 fed-1) combined with foliar application of kaolin or potassium silicate showed the highest significant values of all studied vegetative growth aspects, i.e., stem diameter, relative growth rate, net assimilation rate and leaf relative water content. - Applying 2600 m3 fed-1 combined with foliar application of potassium silicate and 2600 or 1800 m3 fed-1 combined with foliar application of kaolin or potassium silicate significantly increased NPK uptake by sweet pepper plants foliage. - Applying 1000 m3 fed-1 combined with foliar application of kaolin or potassium silicate significantly increased total chlorophyll contents in sweet pepper leaves. - All studied yield characteristics, i.e., number of fruits per plant, average fruit weight, early yield and total yield per feddan as well as water use efficiency were significantly increased by applying 1800 m3 fed-1 of irrigation water combined with foliar application of kaolin or potassium silicate. - The highest significant values of vitamin C, total soluble solids, reducing sugars and total sugars contents in sweet pepper fruits were significantly affected by applying the deficit irrigation treatments (1800 or 1000 m3 fed-1) combined with foliar application of kaolin or potassium silicate. - Fruit flesh thickness was significantly increased by applying 2600 m3 fed-1 combined with kaolin or potassium silicate foliar application. - The highest net return was obtained by applying 1800 m3 fed-1 combined with foliar application of kaolin; such treatment returns the highest benefit-cost ratio (2.51). In conclusion, this investigation demonstrate that irrigation sweet pepper plants with 1800 m3 fed-1 combined with kaolin foliar application (4%, 4 times during the season) could be recommended to improve the vegetative growth characteristics, chemical composition, total yield, water use efficiency and fruit quality, saving about 30% of the total used irrigation water quantity in sweet pepper production. Such treatment can be recommended under drip irrigation system in clay-loam soil at northern of Nil Delta lands, giving the highest net return and benefit-cost ratio to the farmers.