Abstract
Under laboratory conditions, the effect of clay content, plant cover, plant species, seasonal temperature and the size of urea granules on ammonia loss was in-vestigated. Increasing clay content from 15.6 to 31.6% reduced the ammonia loss by 50%. The loss of ammonia from cropped soil was 2.4 times more than that from the bare soil. The average loss of ammonia in soil under Jantar (legume), wheat, euca-lyptus (tree), grass, sugarcane and garden was 19.4, 18.6, 18.6, 13.4, 7.6 and 6.9% N, respectively. The loss of ammonia from soil samples collected in February was 30% Lower than that of samples collected in June, The size of urea granules was found to be directly correlated to ammonia loss.
INTRODUCTION ature and physical condition of urea on am-monia loss from the alluvial alkaline soil.
Presently urea is the major source of nitrogen used for crop production in Pakistan. But it is inferior to other nitrogen fertilizers (Gasser, 1964). Recent research (Vlek and Craswell, 1981) showed that this low efficiency is due to ammonia volatiliza-tion from urea. As the risk of ammonia volatilization is ‘rery high in alkaline soils, there is a need of developing methods for the control of ammonia loss of nitrogen from urea. Changes in the physical environment of the soil influence ammonia volatilization from urea; increasing the bulk density markedly increased hydrolysis of urea (Savant et al., 1987), mulching soil with corn leaves decreased ammonia volatilization (Clay ei a, 1990). The control of ammoniacal loss of nitro-gen warrants the study regarding the contri-bution of various soil parameters and factors in such loss, Thus the objective of this study was to investigate the effect of soil series, plant cover, clay content, seasonal temper-
MATERIALS AND METHODS
In order to study the effect of different soil parameters and factors on ammoniacal loss of nitrogen from urea applied to soil, following laboratory experiments were done. Experiment is Effect of clay content on am-monia volatilization from urea: Two soil samples having 15,6 and 31.6% clay were collected from surface 0-15 cm layer. Wheat crop was growing in both the fields at the time of soil sampling. Experiment II: Effect of plant cover on ammonia volatilization: Soil samples from surface 0-15 cm layer from two adjacent fields (one cropped and one bare) were col-lected. For studying the effect of plant species on ammonia loss soil profile samples in 15 cm depth increments were collected from fields under Jantar (legume), wheat, grass, eucalyptus (tree), sugarcane and gar-den.
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