Nitrogen Mineralization in Texturally Contrasting Soils Subjected to Different Organic Amendments under Semi-Arid Climates

Nitrogen (N) is the prime essential nutrient for agricultural productivity, and its deficiency is overcome through the application of fertilizers. However, the rate of N mineralization from organic N sources is an important process to be monitored for efficient N use and sustainable agricultural management. Laboratory incubation studies were conducted for a period of 150 days to measure N mineralization (N-min) from different organic amendments (OA) in texturally contrasting soils collected at three locations: SL1 (Bahawalpur, sandy loam), SL2 (Bahawalnagar, sandy loam), and SL3 (Rahim Yar Khan, sandy clay loam). A second study was also carried out for 25 days to monitor pH dynamics and ammonia volatilization from the same three OA-treated soils. The results showed that there was no significant difference in net N-min between the soils for poultry manure (PMO) and feather meal (FMO), even if there was a substantial N-min observed for PMC + FMO followed by poultry manure compost (PMC) at SL2 and SL3 soils. This might have happened due to higher microbial biomass carbon (257), nitrogen (61), fungal colonization (88 cfu g(-1) soil) and enzyme activity (79) in SL3 soil receiving PMC + FMO after 150 days of incubation. However, the first-order kinetic model (R-2 = 0.86-0.95) better explained the N-min in all three soils amended with OA (PMC + FMO). The soil pH had more pronounced effects on N-min in all three soils. A non-significant amount of ammonia volatilization was recorded regardless of the initial pH, buffering capacity, and texture variability of the soils. Further study on the particle size of OA and soil pH is warranted to determine the actual effect of OA on N-min.