Effect of crop rotation and cropping history on net N mineralization dynamics of a clay loam soil

Estimating soil N mineralization is critical to being able to balance fertilizer N requirements and their environmental impacts. In this study, net N mineralization was examined in soils under different crop rotations with each phase of the rotation present every year with biologically-based incubations in 2011 and 2015. Net N mineralization was significantly different among treatments when the current crop was soybean and the effect was dependent upon the previous crop and the cropping sequence. In particular, net increases in inorganic N were greater when the previous crop was winter wheat with/without red clover than if it were corn, and greater for the first year of soybean compared to the second year for rotations with two consecutive years of soybean in the 2011 incubation. However, cropping history did not influence net soil N mineralization when the current crop was either corn, winter wheat, or winter wheat + red clover. In 2015, the presence of red clover in the rotation increased net N mineralization in all phases of the rotation. These results suggest both current and previous crops should be considered when estimating the N supplying capacity (net mineralization) of the soil. Net mineralizable N was found to be significantly correlated with total amino sugars (P < 0.001), glucosamine (P < 0.001), and galactosamine (P = 0.003), which suggests that amino sugars could be used as an indicator of the N supplying capacity of soil.

The effect of long-term CO2 enrichment on carbon and nitrogen content of roots and soil of natural pastureland

Increasing levels of atmospheric CO2 may change C and N dynamics in pasture ecosystems. The present study was conducted to examine the impact of four years of CO2 enrichment on soil and root composition and soil N transformation in natural pastureland. Plots of open-top growth chambers were continuously injected with ambient CO2 (350 µL L–1) and elevated CO2 (625 µL L–1). Soil cores exposed to ambient and elevated CO2 treatment were incubated and collected each year. Net N-mineralization rates in soil (NH4 +-N plus NO3ˉ–-N), in addition to total C and N content (%) of soil and root tissues were measured. Results revealed that elevated CO2 caused a significant reduction in soil NO3 (P < 0.05), however, no significant CO2 effect was found on total soil C and N content (%). Roots of plants grown under elevated CO2 treatment had higher C/N ratios. Changes in root C/N ratios were driven by changes in root N concentrations as total root N content (%) was significantly reduced by 30% (P < 0.05). Overall, findings suggest that the effects of CO2 enrichment was more noticeable on N content (%) than C content (%) of soil and roots; elevated CO2 significantly affected soil N-mineralization and total N content (%) in roots, however, no substantial change was found in C inputs in CO2-enriched soil.

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.

Biochar-manure changes N mineralization in a Gray Luvisol used for agricultural production

Biochar is a source of stable organic matter being explored as a manure additive. A 64-day incubation experiment was conducted to quantify the short-term effect of manure (RM), biochar-manure (BM), raw biochar (BC), RM + BC, and BM + BC amendment on soil carbon (C) and nitrogen (N) mineralization. Manure increased CO2-C emission rates, with the highest cumulative CO2-C emissions being observed for RM + BC. Treatments with BM halted soil C mineralization, indicating manure-C stabilization. By contrast, neither RM nor BM affected soil N mineralization. Applying BM might benefit soil C sequestration by lowering CO2-C emissions over the long-term.

Nitrogen availability in biochar-amended soils with excessive compost application

&lt;p&gt;Taking into consideration economic viability, the doses of manure compost in Taiwan are recommended as 1% to 2%; however, some farmers apply more than 2% to 5% in intensive cultivation periods for short-term leafy crops, to add more N. Although many studies report positive effects of a biochar-compost mix on soil properties and plant growth, but there are no studies that have determined the changes in N availability over time after biochar (BC) application in compost over-applicated soil. In the present study, in vitro N mineralization kinetics were examined in further. We tested the hypothesis that BC addition may diminish mixed-soil N mineralization, enhance ammonium retention, reduce nitrate leaching, and decrease P and nutrients loss in compost over-applicated soils. The aim of our research was to evaluate the N and nutrient regulation or enhancement role of different BC addition rates in three compost over-applicated soils over time. The effect of four rates (0%, 0.5%, 1.0%, and 2.0% w/w) of BC co-applied with swine manure compost (5.0% w/w) on three Taiwan rural soils (topsoil, slightly acid Oxisols (SAO), mildly alkaline Inceptisols (MAI), and slightly acid Inceptisols (SAI)) was investigated during 371-d incubation study. BC was produced from lead tree (Leucaena leucocephala (Lam.) de. Wit) at 750 degree C. The incubation results indicated that soil, rate and interaction between soil and rate significantly influenced soil NO3-N and total inorganic N concentrations, but only soil significantly influenced soil NH4-N concentration. Soil NH4-Nand NO3-N concentrations on average during a 371-day incubation followed the order: SAO soil &gt; SAI soil &gt; MAI soil. In most cases the effect was insignificant and inconsistent in terms of time and rate of BC application, rendering it difficult to summarize the effects of BC on ammonium of our investigated soils. The negative effect of BC was prominent almost in all investigated soils during the incubation period and the amount of decline increased as the rate of BC application increased from 0.5% to 2%. In addition, only soil significantly influenced all Mehlich 3-extractable nutrient concentrations, and rate significantly influenced M3-K concentration. At the end of the incubation, adding 0.5% BC and 1.0% BC in SAI soil and 1.0% BC and 2.0% BC in MAI soil both had positive improvement on the nutrients (P, K, Mg, Fe and Mn), and application of BC in SAI soil led to improvement in Cu and Pb (2.0% BC), Zn and N mineralization (0.5% BC and 1.0% BC). In conclusion, the studied results confirmed the potential of biochar-compost blend is promising for preventing excess N and nutrients loss in compost over-applicated soil, as well as maintaining SOC. As adding a large amount of biochar in open fields would be unrealistic and not economically sustainable, we suggested that adding 0.5%~1.0% woody BC to three studied soils should be reasonable and appropriate.&lt;/p&gt;

Multi-cooperation of soil biota in the plough layer is the key for conservation tillage to improve N availability and crop yield

Conservation tillage facilitates constructing a more complex and heterogeneous distribution of soil organisms in the plough layer relative to conventional tillage (CT), which results in an improvement in crop yield and nitrogen (N) uptake. However, knowledge of how soil biota interact to couple mineralization of N and promote plant growth is still limited. The contribution of soil biota (trophic groups and energy pathways) to soil N mineralization and the relationship between energy pathways and grain yield during soybean (Glycine max Merr.) growing season were investigated at 0–5 and 5–15 cm depths under a long-term tillage trial. The trial was initiated in 2001 on a Black soil in Northeastern China and included no tillage (NT), ridge tillage (RT) and CT. A higher contribution of most trophic groups to soil N mineralization throughout the whole plough layer was observed in RT and NT than in CT, and these differences were more pronounced for higher trophic groups than for lower ones. Furthermore, the responses of trophic groups to tillage practices were also transferred into the energy pathways. Bacterial and predator-prey pathways released more mineral N in RT and NT than in CT. Multiple regression models revealed that soybean yield was significantly related to the mineralized N in RT and NT through root, fungal and prey-predator pathways in 0–5 cm and bacterial pathway in 5–15 cm. Additionally, the relative contribution of the mineralized N by different pathways to soybean yield was different in 0–5 cm and decreased in the order of root pathway (0.487) > fungal pathway (0.389) > predator-prey pathway (0.318). Although soil trophic groups coupled with N mineralization and soybean yield varied with depth in RT and NT soils, a stable supply of mineral N from soil to plant could be maintained in the plough layer by the cooperation of predator-prey pathway horizontally with bacterial and plant pathways and vertically with fungal and bacterial pathways. This favorable effect of multi-cooperation of soil biota on coupling N mineralization and plant growth in the plough layer is a cornerstone of conservation tillage benefits in temperate areas of the world.