Effect of Supplemental Nitrogen and Incubation Periods of Animal Manures on Sorghum Growth and Soil Properties@@@تأثير النيتروجين والتحضين للمخلفات الحيوانية على نمو الذرة الرفيعة وخواص التربة

A greenhouse experiment was conducted to evaluate the effects of N amendments. incubation period and manure type on the dry matter production and its content of N, P and K, in sorghum and to detect recent changes in the chemi cal properties of the soil as influenc ed by these param eters. Results revealed that , under all manure types. dry matter yield of sorghum for the first crop was significantly higher than that of the second. Longer incubation periods for chicken and cow manures significantly reduced the dry matter yield compared with the shorter incub ation periods. Und er all manure types, N and P uptake in contrast tothatof K was significantly decreased with prolonging incubation period . Soil organ ic matter content. C:N ratio and soil N , P and K cont ent , were significantl y increased; whereas its pH was reduced ; on the application of each of the studied manures . Meanwhile. prolonging the incubation period had negative effects on C:N ratio and on dry matter of t~e soil and its clement contents. Effects on pH , on the other hand were positive . N-amendment showed no significant effect s.