Effects of different organic materials on forage yield and quality of silage maize (Zea mays L.)

This study was conducted at the experimental area of the Field Crops Department of Çukurova University (37°01′N, 35°18′E) in the 2010 and 2011 growing seasons to determine the effects of sole or combined applications of 3 organic materials (poultry litter, cattle manure, and leonardite) with supplemental inorganic fertilizer on the forage yield and quality of silage maize. The field trial was arranged in a complete randomized block design with 3 replications. Poultry litter (PL) and cattle manure (CM) were applied based on P or N requirements (PL-P, PL-N, CM-P, and CM-N) of the crop, whereas leonardite was applied in only 1 dose (500 kg ha^–1) and was also combined with 3 inorganic fertilizer doses (100%, 75%, and 50% of the recommended inorganic fertilizer dose, called LEO-100, LEO- 75, and LEO-50, respectively). The results show that the highest values of dry matter (DM) and crude protein (CP) yields (18.3 t ha^–1 and 1652 kg ha^–1, respectively) were observed in LEO-100, whereas the lowest (11.2 t ha^–1 and 758 kg ha^–1, respectively) were observed in PL-N. In terms of forage quality parameters (CP, acid detergent fiber, neutral detergent fiber, and relative feed value), the P-based poultry litter and cattle manure treatments (PL-P and CM-P) gave similar results to conventional fertilization treatment, whereas the N-based treatments (PL-N and CM-N) significantly decreased forage quality. The combined use of organic materials with inorganic fertilizers instead of a conventional fertilization regime may be effective in maintaining forage supply but N-based treatments have the risk of restricting forage production from silage maize.