Prieto-Prieto, Ricardo J.

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    Efecto del manejo de nitrógeno sobre características agronómicas, composición química y fermentativas de híbridos de maíz a diferentes edades de corte
    (2007) Prieto-Prieto, Ricardo J.; Valencia-Chin, Elide; College of Agricultural Sciences; O'Halloran, Julia; Beaver, James; Muñoz, Miguel A.; Department of Agricultural and Biosystems Engineering; Orellan, Lynette
    The dairy cattle industry in Puerto Rico lacks forages of high nutritive value. Maize silage is a high energy value crop and offers potential for use in the industry, but its low protein concentration is a major concern. Information on use of organic or inorganic fertilizer and their effect on yield, nutritive value and fermentation characteristics of hybrid corn (DKC 67-60) grown for silage are limited. Two experiments were conducted. The first experiment consisted of a maize planting to evaluate the effect of four N systems [conventional fertilization (CF; 185 kg/ha of 15-5-10), Maize-Mucuna (MM; Mucuna pruriens cv Vine 90-d), and two dairy 12 of effluent rates (DFR ; 56 and DFR ; 112 kg N/ha) and harvesting at three growth stages (70, 77 84 DAP) on plant components (leaf, stem, ear), total yield, nutritive value and fermentation and aerobic stability of the corn silage. There was an effect (P<0.05) on leaf yield and total dry matter yield. Leaf yield was greater with CF. Total dry matter yield was also 1 t/ha higher with CF than other N systems. There was no effect of date of harvest on the variables measured, except for the leaf component. Crude protein concentration was greater with CF (8.67%) surpassing by two units the organic fertilization, but there was not effect on NDF. Harvest age did not affect CP concentration, but did have an effect on NDF. Maize harvested at 84 DAP (59.56 %) was higher than harvested at 77 DAP (58.4 %) or 70 DAP (56.15 %). The N treatments did not affect pH and organic acids of hybrid maize DKC 67-60 silage, presenting typical characteristics of anaerobic fermentation (pH 4.2; and adequate lactic acid production). The second experiment consisted of two maize plantings. The effects of four N levels (0, 56, 112 and 185 kg of N/ha from 15-5-10 source) y three harvest dates (70, 77 y 84 DAP) on dry matter yield (DMY) of leaves, stem, ear and total yield, nutritive value (CP and NDF) of corn harvested prior to ensiling were determined. A second objective evaluated the same treatment effects on fermentation characteristics and aerobic stability of hybrid corn Dekalb (DKC 67-60). In both plantings the levels of N affected dry matter yields of leaves, stems, ears and total yield, exhibiting a quadratic response. This suggests that optimum N rate is between 112 and 185 kg/ha. Harvest date had an effect (P<0.05) on corn, stems, ears and total yield, but had no effect on leaves. Greater DMY were observed at 84 DAP. The CP concentration was greater in first in the first planting. Crude protein increased (2 unit differences over the control) with increasing N rates, but N rates had no effect on NDF. Harvest date had no effect on CP, but as expected there was increase in NDF with increasing harvest date. Both pH and the organic acids were similar for the N levels, indicating a good fermentation characteristic. There was no effect of N or harvest date on aerobic stability. In conclusion, irrespective of the type of N (organic or inorganic) the hybrid corn DKC 67-60 requires between 112-185 kg/ha of N for optimum yield y high nutritive value and its recommended that the corn be harvested between 70 to 77 DAP.