Effect of phosphogypsum on N-froms and the contribution of nonexchangeable NH4 in supplying nitrogen to barley plants grown on calcareous soils
1993
Aziz, F.G. (Industrial Forest Project Executive Committee P.O.Box.4289, Baghdad (Iraq)) | Rahi, H.S. | Mohammad, B.I. (Baghdad Univ. Coll. of Agric. (Iraq))
A study of N uptake by barley grown in apot experiment along with incubation-extraction studies were carried out on different soils from 18 locations representing cultivated calcareous soils of Iraq. The contribution of nonexchangeable NH4 to plant uptake and the "recently" NH4 fixation from the mineralizable N as well as effect of phosphogypsum on these N fractions were investigated. The result showed that the nonexchangeable NH4 content of the soils decreased at the end of growing period. The average decrease over all the soils was 13.1 mg (-1 is power of kg) which formed about 7 from the native nonexchangeable NH4. The contribution of released nonexchangeable NH4 and N fractions to N uptake was estimated by calculating the ratio of standared partial regression. However,the combination of inorganic N,mineralizable N and released nonexchangeable NH4,showed the highest ratio (2.03) phosphogypsum application caused increase of 17.4 in mean values of minerlizable N. The "recently"fixed NH4 could be account for about 38 of the mineralizable N.This was decreased to 19 in the presence of phosphogypsum
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