N, P AND K REMOVAL BY VEGETABLE CACTUS PEAR CULTIVATED WITH DAIRY MANURE UNDER DRIP IRRIGATION

Field experiments were carried out in Gómez Palacio, Durango, México from April 2001 to March 2002 to determine monthly and annual amount of N, P and K removed by vegetable cactus pear ‘Variety 69’. All experiments were fertilized with dairy manure and irrigated utilizing a drip irrigation system. Three water levels were applied to replenish 30, 45 and 60% of the daily evaporation as measured by a Standard Type “A” tank. All plots received 107 t ha^-1 of dairy manure (1.55%, 0.55% and 2.88% of N, P and K, respectively) split in two applications (January, 2000 and April, 2001). Experimental units consisted of four rows (4 m long, 0.6 m between rows and 0.4 m between plants) of cladodes. The experimental design consisted of randomized blocks with three replications. The two center rows were harvested every month, except January, to obtain the yield of fresh cladodes. A sub-sample of each plot was oven-dried at 65°C until constant weight to calculate dry matter yield. These samples were analyzed to determine total N, P and K concentrations. Nutrient removal was calculated by multiplying dry matter yield by N, P and K concentrations. Results showed fresh monthly yields reached 163 t ha^-1 under the 30% evaporation treatment. However, the highest yields were obtained with the 45 and 60% evaporation levels. After averaging irrigation treatments, ‘Variety 69’ removed 155.7, 58.3 and 879.2, kg ha^-1 yr^-1 of N, P and K, respectively. The high level of nutrients removed can be explained by the htenayield when cactus pear is cultivated without restrictions of water or nutrients. The amounts of N, P and K removed can be used as a base to determine fertilizer recommendations for the species.