Response of maize to poultry manure in combination with urea fertilizer under three hill distances

Two field experiments were conducted during the two successive seasons of 2003 and 2004 to study the effect of poultry manure in combination with urea fertilization, hill distance and their interaction on maize productivity. Each experiment included 18 treatments, which were the combinations of : six N treatment (kg/ha) as follows : 0.0 N (N1), 120 kg N as poultry (chicken) manure (N2), 30 kg N as urea + 90 kg N as poultry manure (N3), 60 kg N as urea + 60 kg N as poultry manure (N4), 90 kg N as urea + 30 kg N as poultry manure (N5) and 120 kg N as urea (N6) and three hill distances, i.e. 20, 25 and 30 cm between hills, representing theoretical plant densities of 71429, 57143 and 47620 plants/ha, respectively. Results could be summarized as follows : Supplying maize plants with N (either as urea, poultry manure or their combinations) significantly increased all studied traits comparing with no N fertilization. Adding the whole N amount as ur ea (N6) or increasing the proportion of N as urea (to greater than equivalent to 50%) of the applied N amount in the fertilizer combinations (N4 and N5), further increments in grain yield were achieved. Marked increases were obtained by widening hill distance from 20 to 25 cm (in ear height), 20 to 30 cm (in LA, stem and ear diameter), 20 to 25 or 30 cm (in ear length and rows number/ear) and from 20 or 25 to 30 cm (in grains number/row). However, the shortest distance (20 cm between hills) markedly shortened plant height and produced more grain and straw yields than the wider ones (i.e. 25 and 30 cm between hills). Moreover, alternating the distance between hills did not affect 100 grain wt. All studied traits were significantly affected by the interaction between N fertilization treatments and hill distance where, the N-fertilized treatments surpassed the unfertilized ones under each hill distance.