Vertical distribution of soluble organic nitrogen, nitrogen mineralization, nitrification, and amidohydrolase activities in a manure‐treated soil

Abstract

Recent studies indicate that soil soluble organic nitrogen (SON) plays an important regulatory role in the soil-plant N cycle. The aims of this study were to identify the vertical distribution of SON and its correlation with N mineralization, nitrification, and amidohydrolase activities, in a soil repeatedly amended with cow manure or chemical fertilizer. For this purpose, soil samples were collected from 0-20, 20-40, 40-60, 60-80, and 80-100 cm depths of a calcareous soil, which has been annually amended for 5 y with cow manure (CM) at two rates of 50 (CM 50 ) and 100 (CM 100 ) Mg CM ha -1 y -1 . Treatments with chemical fertilizer (CF) and a control (CT) were also included. Soluble organic N, N mineralization, nitrification rates, as well as L-glutaminase and L-asparaginase activities were determined. Both CM 50 and CM 100 enhanced SON content throughout the soil profile. Nitrogen-mineralization rate (N m ) was increased at the 0-20 cm depth of the CM 100 treatment and remained unaffected at the deeper depths. Nitrification rate (N n ) was significantly higher at the 0-60 cm depth of CM 100 compared to CF and CT. L-glutaminase and L-asparaginase activities were significantly increased at the 0-40 cm depth in both CM 50 and CM 100 compared to CF and CT. The amidohydrolase activities could not be detected below 40 cm, regardless of the fertilizer treatments. Our results suggest that SON makes a minor contribution to N mineralization in deep soil layers. It was also concluded that changes in the SON throughout the soil profile were not associated with changes in the N-transformation rates (N m and N n ) and amidohydrolase activities. While we conclude that SON is a major N pool in the whole profile of the manure applied soil further investigation is required to characterize SON and to investigate the bioavailability of SON for microbial activity in different soil depths.

Assessing the Response of Tomato Yield, Fruit Composition, Nitrogen Absorption, and Soil Nitrogen Fractions to Different Fertilization Management Strategies in the Greenhouse

“…The current general consensus is that manure application leads to a substantial increase in soil N mineralization potential and enhances the activity of heterotrophic microorganisms in the added organic manure; subsequent turnover of this microbial population will lead to the production of NH 4 + -N (Bonkowski et al, 2000). Additionally, manure preserves a certain amount of mineral N and dissolved organic N (Khalili and Nourbakhsh, 2012), both of which are continuously released from the manure due to mineralization, thereby increasing the soil Table 3. Stepwise regression analysis between N fractions and fruit yield during the tomato growth period.…”

Manure increase the leaching risk of soil extractable organic nitrogen in intensively irrigated greenhouse vegetable cropping systems

“…A soil with a history of chicken-manure application increased EON significantly in the 0-150 cm soil profile compared to the same soil without manure addition (Shepherd et al 2001). A study from Khalili and Nourbakhsh (2012) even showed that EON was a major N pool in the whole profile of the manure applied soil. Meanwhile, manure application also results in more leaching of N than chemical fertilizer application at the same rate of N input (Chen et al 2005;van Kessel et al 2009).…”

Influence of long-term application of stockpiled feedlot manure with straw or wood-chip bedding on net nitrogen mineralization and nitrification in a clay loam soil

“…Soil nitrification rates have been extensively measured in manured soils (Laanbroek and Gerards 1991;Nugroho and Kuwatsuka 1992;Paul et al 1993;Shi et al 2004;Calderón et al 2005;Habteselassie et al 2006;Khalili and Nourbakhsh 2012). Most studies have generally reported greater nitrification rates for amended than unamended or inorganic fertilized soils.…”