Timing and Manure Nitrogen Credits in a Daily Haul System
Many dairy producers still employ a daily haul manure application system. Typically, fields receive manure from the time crops are harvested in the fall until the new crop is planted in the spring. This management system begs the question of whether nitrogen credits from the manure remain the same regardless of application timing. A 3-year study at the LancasterResearch Station addressed this question. In each of the three years (1992-94), manure was applied at a single rate (35 tons per acre of fresh manure) without incorporation in November, January, and March. Another treatment was applied at the same rate in mid-April and incorporated within 4 to 12 days. Results from these treatments were compared with those from several rates of pre-plant applied urea fertilizer (75, 125, or 175 lbs. per acre) and an untreated control. In each year the fields had been corn the previous year and had received no manure for two years before the study began. Results When optimal and comparable nutrient rates of manure and commercial fertilizer were applied, equal yields were usually obtained. Grain and silage yields during the 1992 and 1994 growing seasons showed that the manure provided a substantial amount of nutrients to fertilize the corn crop and top yields were comparable to those achieved with the commercial nitrogen. Additionally, yields from fall or winter applied manure were similar to those from spring applied manure. In 1993, nutrient availability from the manure was substantially less than it was in the other years. Top yields from manure treatments did not equal those achieved with commercial fertilizer. In addition, fall applications appeared to perform best. This poorer performance was most likely a result of slower than normal release of available manure-N in a year that was exceptionally cool and wet during the spring. Bottom line: Some key management related conclusions from this study are as follows:
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