• Author / Uploaded
• Estefany Hinojosa

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APPLYING IRRIGATION TECHNOLOGY TO CITRUS CULTIVATION Three year trial son a mature orange grove have shown that yields were highest when the wetted area was the smallest, for the same quantity of wáter and fertilizer. Varying the fertlizer and wáter applications affected yield and quality. ABSTRACT The effect of fertigation under partial wetting of the root zone, on yield respance and quality of Shamouti sweet orange (Citrus sinensis (L)) is being investigated in a long term experiment begun in 1978, in a mature grove in Nordie in the coestal plain of Israel. Three different wetted áreas of about 35%, 70% and 90% were obtained by means of low pressure and regular sprinkier. Three amounts of irrigation water 550, 750 and 900 mm (ET-25% ET and ET+20%) were applied at 7 day intervals, from early April until mid-November. In the medium irrigation treatment in all three wetted soil areas, three levels of nitrogen, 15, 35 and 69 ppm, were applied throungh the irrigation system until the end of July. The various soil moisture and fertilizer regimes affected citus production and quality. The highest nitrogen application gave a significantly higher yield than the lower rates. The low water application produced a lower yield than the two higher applications. The average yield in the 1980 season was 83.1, 74.8 and 73.7 ton/ha in the 35%, 70% and 90% wetted áreas. Fruit quality and the total soluble soilds-to-acid ratio was not affected considerably. However, in plots with the highest leved of nitrogen, greening of the fruit and an increase in peel thickness was observed. The various fertilizer levels affected mineral content in soil, leaves and fruit. Tree growth, leaf water potential and root distribution were affected mainly by irrigation treatment. ET=(Evapotranspiration) Introduction Citrus culture, practised on almost every continent, is limited by constantly depleting water resources and the increasing cost of irrigation waternand fertilizers. Advances in citrus management relative to these two resources have contributed significantly to the attainment of increesped citrus production during the last decase. The irrigation and fertililization practices in citrus culture are basedon long horticultural tradition and extensive research. However, changes in irrigation and fertilization technology require a reassessment of the traditional practices. The introduction of solid set, microjet or drip systems provide much better control of water and fertilizer application (Tend to increase the water use efficiency ). The modern solid set systems make it possible to apply fertilizers through the irrigation system and provide a frequent supply of nutrients to the trees. These new methods gave rise to the concept of fertigation under partial wetting of the root zone. The effect of partial wetting and various levels of nitrogen (applied through the irrigation system) on the yield and quality of shamouti orange is being investigated.

The results obtained in the 1978, 1979 and 1980 seasons are presented and the relations between water and fertilizer supply, water use efficiency and citrus yield response and their implications for optimum citrus production are discussed. Materiales y métodos The experiement was begun in April 1978 in a 16 year old Shamouti orange grove. The planting distance is 4 x 6 m. The planting distance is 4 x 6 m. The soil is Sandy to Sandy loam Hamra on a Sandy subsoil. The climate is Mediterranean with an average anual rainfall of 500 mm confined to the November-March period. The raintess irrigation season is from April to November. The long long term mean deily evaporation rate from a U.S. Weather Buresu Class. A pan is 5.1 mm in April 6.0 mm in May, 7.5 mm in june, 7.2 mm in july, 6.8 mm in August, 5.9 mm in September and 4.1 in october. The year to year deviations from these values are minon. The experimental treatments are presented in table 1. The three wetted areas of about 35%, 70% and 90% were obtained by means of microsprayer (S) low pressure microsprayers (M) and regular sprinklers (L), respectively. Three seasonal amounts of irrigation water, about 550 (I1), 750 (I2) and 900 (I3) mm were applied at 7 day intervals from early in April until the end of october. The médium amount of irrigation water, I2, 750 mm (0.6 of class a pan evaporation), was set according to local irrigation treatment, in ail three wetted soil áreas, 3 lavals of nitrogen , N1=15ppm, N2=35 ppmand N3= 60 ppm were applied through the irrigation system until the end of july. Ail nitrogen levels included the 10 ppm N-NO3 of the local well water. The fertilizers were applied by means of a proportional fertilizer pump (T.M.B.Pump). Nitrogen was applied as NH4, NO3 solution, potassium as KNO3 and phosphorus as ammonium poly