Effect of amendment of manure and corn residues on soil N mineralization and enzyme activity

Understanding the effect of manure and crop residue application on N mineralization in soil is crucial in order to minimize nitrate contamination of surface and groundwater. Besides, developing an alternative management practice for corn residue burning is of great importance and needs more knowledge about inorganic N dynamics. Here we conducted a laboratory experiment to study the effect of corn residue application on inorganic N dynamics and soil enzyme activities in soils with different manure fertilization histories. The laboratory experiment was a combination of 3 fertilization histories of: 0, 50 and 100 Mg cow manure ha$^{-1}$ year$^{-1}$ for five consecutive years; and 3 residue treatments including: no residue, corn shoot and corn root application. We monitored inorganic N periodically during 20 weeks of incubation. We also monitored the activities of urease, L-asparaginase, L-glutaminase and $\beta$-glucosidase before and after incubation. Our findings show that for residue-amended soils, inorganic N decreased in the first 2 weeks of incubation by 50 to 86%, followed by a gradual increase. In contrast, for control soils without residue amendment, the inorganic N concentration increased from 64 to 86% during the first week of incubation. Our results thus show that the application of corn residues can control the flush of inorganic nitrogen and reduce the potential of nitrate leaching in manure-applied soils. Furthermore, manure application at the highest rate increased the activity of urease by 47%, L-asparaginase by 70%, L-glutaminase by 60% and $\beta$-glucosidase by 78%. $\beta$-glucosidase increased due to corn shoot application by about 8% and was the most responsive enzyme to the treatments. Overall, the enzyme activities were more influenced by manure application history than corn residue application

A Simple and Rapid Method to Evaluate Potentially Mineralizable Nitrogen in Sewage Sludge Amended Calcareous Soils

Potentially mineralizable nitrogen (PMN) can be usually considered as labile nitrogen. Measurement of PMN is expensive and time consuming; therefore, a simpler and more rapid alternative may facilitate routine laboratory analysis. The objective of this study was to determine the relationship between PMN and biological index of nitrogen availability (BINA). The studied soil was previously treated with 0, 25, and 100 tons ha-1 of sewage sludge with 0, 1, 2 and 3 consecutive years of application. Soil samples were taken 6 months after the latest application. PMN was measured according to Stanford and Smith procedure (20 weeks of aerobic incubation with 2 weeks leaching intervals) and BINA measured as described by Bundy and Meisinger (7 days of anaerobic incubation at 40˚ C followed by extraction of NH4+). Results showed that PMN was significantly correlated with BINA (r = 0.938,

The role of Hackberry "Celtis caucasica" as nitrogen-fixing trees on understory’s soil properties in reserved area in Ardasteh-Dehaghan in Isfahan

Nitrogen-fixing trees (NFT) or trees that have the ability to sequestrate nitrogen in soil, could increase organic matter in the understory’s soil. These trees can increase fertility of soil by adding large amount of nitrogen to soil and also supply necessity of the understory’s plants or NFTs to this element. This study was conducted to investigate the role of “Celtis caucasica” as nitrogen-fixing tree on understory’s soil fertility and plants in a reserved area called Ardasteh-Dehaghan at Isfahan province of Iran. For this reason, soil sampling was made from two locations (the tree’s understory and outside it or control) and three depths from soil surface (0-20, 20-40 and 40-60 cm) under the randomized complete blocks statistical design. The studied soil properties consisted of: pH, EC, CaCO3, organic carbon, mineral nitrogen, total nitrogen and particle density. Furthermore, a criterion plant from the tree’s understory was analyzed at laboratory scale to test effects of the trees on amount of total nitrogen, protein and plant production. Results showed that the greatest amounts of soil’s lime, mineral nitrogen and total nitrogen as well as the criterion plant’s organic carbon, total nitrogen, protein and production was gained at soil depth of 0-20 cm of the hackberry’s understory. These amounts were reduced as soil depth increased

Effect of Sewage Sludge on Nitrification Rate and Corn Nitrogen Uptake

Land application of sludge is a primary means of disposing municipal and industrial sewage sludge. The objectives of this research were to determine the effect of cumulative and residual sludge application on nitrogen (N) mineralization and nitrification and corn N uptake in a sludge amended clay loam soil (fine loamy, mixed thermic Typic Haplarigid). Soil samples from 0-15 cm depth were collected in a field that had received sewage sludge once, twice or three times during 1999-2001 at 0, 25, 50, and 100 mg ha-1. Rates of nitrification and N mineralization were determined in incubated soil samples. Corn N uptake was also measured. The results showed that sewage sludge application significantly increased soil organic carbon, N mineralization and nitrification. Also, corn yield and N-uptake increased significantly with sludge rates and number of times of sludge application. Regression analysis indicated significant correlations between soil organic C  and rate of nitrification (r= 0.825,

Effect of fiber length on mechanical properties of wood composite plastic (Polypropylene)

The objective of adding reinforcing fillers, such as natural fibers to plastics is to increase the strength compared with neat plastic and wood. In this research the effect of wood pulp fiber length (short, medium and long), aspect ratio and fiber content (27%, 37%, 47% and 0% (non-reinforced PP)) with 3% maleic anhydride grafted polypropylene on wood plastic composites (WPCs) has been studied.   Results showed that increased fiber length or aspect ratio and fiber content increases mechanical properties (tensile strength, tensile modulus and MOE). Impact strength had an inverse correlation with fiber content and fiber length, but fiber content was a much more important factor than fiber length for impact strength. The impact strength of composite of softwood pulps was much higher than wood floor composite plastic. The significant interaction between fiber length and fiber content, and the lack of a specific trend in the treatments made assessment of the effect of fiber properties on MOR difficult

Symposium no. 29 Paper no. 118 Presentation: poster 118-1

and 12.1 to 24.9%, respectively. Urease was significantly (p<0.01) less inhibited by Cr than Cd and Pb, whereas Cd and Pb did not reveal any significant difference in all five soils. L-asparaginase and urease activities appeared as sensitive indicator of soil biochemical quality in soils contaminated with heavy metals. Keywords: L-asparaginase, urease, trace metals, N-mineralization Introduction The nitrogen (N) cycle in soils includes many biochemical and enzyme mediated reactions. Nitrogen mineralization is an important process of N cycle that includes mostly a group of hydrolases. L-asparaginase catalyzes the hydrolysis of L-asparagine to L-asparatic acid and ammonia, urease catalyzes the hydrolysis of urea to ammonia and carbon dioxide. Microorganisms, plants and animals contribute to soil Lasparaginase (Frankenberger and Tabatabai, 1991c; Tabatabai, 1994) and urease (Baligar et al., 1991; Rao and Ghai, 1985; Reynolds et al., 1985) activities. Urea is one of the most impor