Kinetic of Nitrogen Mineralization by Using Various Organic Manures of Pune Region, Maharashtra

The mathematical description of N mineralization in soils like parabolic model, exponential model, hyperbolic model, zero order models etc, is a possible 3 approach to characterize and quantify the organic matters pool and mineralization constant rate. The single exponential model most widely used for soil N mineralization, although other types have also been tested. Several kinetic models are often used to estimate the kinetic of N mineralization, thus a model is selected based on the highest coefficient of determination (r2) and the lowest standard error (Wijanarko & Purwanto, 2016). The N mineralization capacity through long term incubation procedures. From their studies they proposed an asymptotic model of time course of N mineralization, making it possible to calculate the N mineralization potential of the soils (Stanford & Smith, 1972). Kinetics parameters in mineralization study can be potentially used to access the mineralization-immobilization process in soils under varying environmental and management conditions. Nitrogen-use efficiency can be enhanced through the understanding of N-mineralization potential of different organic source.

How does measuring methodology impact N mineralization in controlled conditions and relations to soil biological parameters: air dried versus fresh soil

<p>Predictions of N mineralization are still difficult but maybe this is due to the methodologies. Many soil tests have been proposed to predict N mineralization between field and laboratory experiment. Incubations of soil in the laboratory under controlled environmental conditions are most commonly used to assess N mineralization rates both from SOM and from added organic materials. However, predicting N mineralization due to the methods (the impact of using air-dried and fresh soil) has never been assessed before. If the results differ between the methods commonly used, there is a serious problem. Therefore, the objective of this study was to evaluate the influence of the incubation methods (air-dried vs fresh soil) to predict N mineralization. The N mineralization potential from fifteen agricultural soils in West and East Flanders – Belgium, were determined by aerobic incubation methods used air-dried and fresh soil at (20 – 25<sup>0</sup>C) for 84-days in the laboratory. The results indicated that total mineral nitrogen (NH4<sup>+</sup> + NO3<sup>-</sup>) concentrations and carbon content of microbial biomass (MBC) did not differ significantly between these methods. Nitrogen was mineralized in fresh soil incubations (0.36 mg N. kg<sup>-1</sup> soil day <sup>-1</sup>) while in air-dried soil (0.31 mg N kg<sup>-1</sup> soil day <sup>-1</sup>). Thus, the results generate that it may be conceivable to predict N mineralization by these two methods in controlled conditions.</p>

Integrating Management of Soil Nitrogen and Weeds

Knowledge of the soil nitrogen (N) supply and the N mineralization potential of the soil combined with an understanding of weed-crop competition in response to soil nutrient levels may be used to optimize N fertilizer rates to increase the competitive advantage of crop species. A greenhouse study (2006) and field studies (2007 to 2008) in Illinois and Nebraska were conducted to quantify the growth and interference of maize and velvetleaf in response to varying synthetic N fertilizer rates in soils with high and low N mineralization potential. Natural soils were classified as having “low mineralization potential” (LMP), while soils amended with composted manure were classified as having “high mineralization potential” (HMP). Maize and velvetleaf were grown in monoculture or in mixture in both LMP and HMP soils and fertilized with zero, medium, or full locally recommended N rate. In the greenhouse, velvetleaf interference in maize with respect to plant biomass increased as N rate increased in the HMP soil, whereas increasing N rate in the LMP soil reduced velvetleaf interference. In contrast, velvetleaf interference in maize decreased as N rate increased regardless of soil class in the field experiment. With respect to grain yield, velvetleaf interference in maize was unaffected by N rate or soil class. In both greenhouse and field experiments, velvetleaf biomass was greater in the HMP soil class, whereas maize interference in velvetleaf was generally greater in the LMP soil class. While soil N levels influenced weed-crop interference in the greenhouse, the results of the field study demonstrate the difficulty of controlling soil nutrient dynamics in the field and support a maize fertilization strategy independent of weed N use considerations.

Effects of experimental freezing on soil nitrogen dynamics in soils from a net nitrification gradient in a nitrogen-saturated hardwood forest ecosystem

This study examined effects of soil freezing on N dynamics in soil along an N processing gradient within a mixed hardwood dominated watershed at Fernow Experimental Forest, West Virginia. Sites were designated as LN (low rates of N processing), ML (moderately low), MH (moderately high), and HN (high). Soils underwent three 7-day freezing treatments (0, –20, or –80 °C) in the laboratory. Responses varied between temperature treatments and along the gradient. Initial effects differed among freezing treatments for net N mineralization, but not nitrification, in soils across the gradient, generally maintained at LN < ML ≤ MH < HN for all treatments. Net N mineralization potential was higher following freezing at –20 and –80 °C than control; all were higher than at 0 °C. Net nitrification potential exhibited similar patterns. LN was an exception, with net nitrification low regardless of treatment. Freezing response of N mineralization differed greatly from that of nitrification, suggesting that soil freezing may decouple two processes of the soil N cycle that are otherwise tightly linked at our site. Results also suggest that soil freezing at temperatures commonly experienced at this site can further increase net nitrification in soils already exhibiting high nitrification from N saturation.