Quantifying the effect of soil organic matter on indigenous soil N supply and wheat productivity in semiarid sub-tropical India

2007 ◽  
Vol 79 (2) ◽  
pp. 103-112 ◽  
Author(s):  
D. K. Benbi ◽  
Milap Chand
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil N ◽  
N Supply

scholarly journals Factors influencing the soil-plant nitrogen cycle of hill pastures under conventional and organic management

2003 ◽  
pp. 195-198
Author(s):  
R.L. Parfitt ◽  
G.W.Yeates D.J. Ross ◽  
A.D. Mackay ◽  
P.J. Budding
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
N Mineralization ◽  
Dominant Factor ◽  
Net N Mineralization ◽  
Soil N ◽  
Organic Management ◽  
N Supply ◽  
Wide Range

Nitrogen (N) is the major nutrient that limits pasture growth in New Zealand. Here we test the hypothesis that N supply to herbage from soil microbial mineralization is a function of both the quantity and quality of the soil organic matter, and that this underlying process is similar under conventional and organic management. Preliminary results for October- November 2002 from nine sites with a wide range of soil N status at AgResearch, Ballantrae show that microbial-mineralized N supply from the soil to herbage was the dominant factor controlling the differences in herbage growth. Herbage N was also highly correlated with the soil N supply, as estimated from a 56-day laboratory incubation of soil (0-7.5 cm, and 7.5-20 cm depths). For these soils, spring herbage production could be estimated from the negative relationship with the C:N ratio of the topsoils. This suggests the over-riding factor in the N supply at the nine sites was the quality of soil organic matter in the topsoils. Quality is enhanced through the growth of legumes that in turn depend on the P status of the soil. The soil parent material at some sites (1996 organic farmlets) is calcareous mudstone, which has a high P status, and may explain some differences in site fertility not explained by past P applications. The relationship between the quantity and quality of organic matter and microbial N mineralization in the four farmlets that had organic management appeared to be on the same trend-lines as those in the conventional farmlets, indicating that the underlying net N mineralization process was similar under conventional and organic management. Other factors statistically related to herbage yield and soil net N mineralization were some groups of nematodes and microbial P, but not microbial biomass C or N. Keywords: N mineralisation, non-chemical farms, organic farms, soil fertility

Integrating principles of nitrogen dynamics in a method to estimate leachable nitrogen under agricultural systems

2006 ◽  
Vol 53 (2) ◽  
pp. 289-301 ◽  
Author(s):  
M. Burkart ◽  
D. James ◽  
M. Liebman ◽  
E. van Ouwerkerk
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Soil Organic Matter ◽  
Nitrogen Mineralization ◽  
Crop Residue ◽  
Nitrogen Flow ◽  
Soil N ◽  
Agricultural Systems ◽  
Nitrate N ◽  
Agricultural Regions

Surplus nitrogen (N) in ground and surface water is of concern in intensive agricultural regions. Surplus N leaches during lengthy periods where annual crop systems are used in temperate regions. This paper presents a model to estimate the surplus N available for leaching to ground water beneath agricultural systems and applies the model to watersheds in an intensive maize and soybean production system. The model utilizes commonly available georeferenced data on soils, crops, and livestock, making it applicable to watersheds in many regions. The model links stocks of N in soil, crops, livestock, fertilizer and the atmosphere. Nitrogen flow centers on exchange between the soil N stocks. Nitrogen mineralization rates are defined for three soil organic matter pools, crop residue, and manure based on carbon:N ratios. Nitrogen exports from the system are harvested crops, livestock and losses to the atmosphere. Application of the model in 26 Iowa watersheds finds surpluses of 18 to 43 kg-N/ha. Surpluses exceeded measured annual nitrate-N loads in regional streams by amounts equivalent to denitrification rates in groundwater. Deficits in soil N were sufficiently small to suggest that the system is in equilibrium with soils of the region.

Resolving the spatial variability of soil N using fractions of soil organic matter

2012 ◽  
Vol 147 ◽  
pp. 66-72 ◽  
Author(s):  
Carolin Córdova ◽  
Saran P. Sohi ◽  
R. Murray Lark ◽  
Keith W.T. Goulding ◽  
J Steve Robinson
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Spatial Variability ◽  
Soil N

Total soil organic matter and its labile pools following mulga (Acacia aneura) clearing for pasture development and cropping. 2. Total and labile nitrogen

Soil Research ◽  
2005 ◽  
Vol 43 (2) ◽  
pp. 179 ◽  
Author(s):  
R. C. Dalal ◽  
B. P. Harms ◽  
E. Krull ◽  
W. J. Wang ◽  
N. J. Mathers
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Light Fraction ◽  
Organic N ◽  
Soil N ◽  
Organic Matter Quality ◽  
Organic C ◽  
Total Soil ◽  
Acacia Aneura

Mulga (Acacia aneura) woodlands and open forests occupy about 150 Mha in Australia, and originally occupied 11.2 Mha in Queensland. Substantial areas (1.3 Mha) of the mulga vegetation have been cleared in Queensland, mostly for pasture production, but some areas are also used for cereal cropping. Twenty years after mulga clearing we found a significant loss of total soil organic C (28–35% from the 0–0.05 m depth) and light fraction C (>50% from the 0–1 m depth) from soil under pasture and cropping at a site in southern Queensland. We report here the changes in soil N and labile N pools in a paired-site study following conversion of mulga to buffel pasture (Cenchrus ciliaris) and cereal (mostly wheat) cropping for more than 20 years. Conversion from mulga forest to pasture and cultivation resulted in greater losses of soil N than organic C in the top 0.1 m depths. As a result, C/N ratios in soil under both pasture and cropping were higher than soil under mulga, indicating a decline in soil organic matter quality after mulga clearing. Although land-use change had no significant effect on 15N natural abundance (δ15N) values of total soil N down to a depth of 1 m, δ15N values of wheat tops and roots indicated that the primary source of N under cropping was soil organic N, while that of buffel pasture was a mixed source of soil N and decomposed litter and root N. Light fraction N (<1.6 Mg/m3) declined by 60–70% throughout the 1 m soil profile under pasture and cropping, but it was 15N-enriched in these 2 land-use systems. The δ15N values of mulga phyllodes, twigs, and fine roots, indicated an input of atmospheric fixed N2 that was estimated to be about 25 kg N/ha.year. However, the source and magnitude of this N resource needs to be confirmed. Soil N losses were estimated to be 12 kg N/ha.year under pasture and 17 kg N/ha.year under cropping over a 20-year period. These findings raise the issue of the long-term sustainable use of cleared mulga areas for pasture and/or cropping. The labile C and N pools and N mineralised also declined, which would have an immediate adverse effect on soil fertility and plant productivity of cleared Mulga Lands, as well as reducing their potential as a soil sink for greenhouse gases.

scholarly journals Effect of grassland management on the amounts of soil organic N and C.

1991 ◽  
Vol 39 (4) ◽  
pp. 225-236 ◽  
Author(s):  
J. Hassink ◽  
J.J. Neeteson
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
The Netherlands ◽  
Grassland Management ◽  
Fertilizer Application ◽  
Management Systems ◽  
Organic N ◽  
Soil N ◽  
Loamy Soil ◽  
Total Soil N

The effects of different management systems on soil organic N and C contents were studied on a sandy and loamy soil given various amounts of N fertilizers under rotational grazing, in the Netherlands. Differences in total soil N and C between grazed and mown fields were also investigated. On the loamy soil grazed plots N accumulated at 245 kg/ha per year, irrespective of the rate of applied N. Four years after the experiment was initiated both soil N and C contents were considerably higher under grazing than under mowing. The C/N ratio of soil organic matter was higher without N fertilizer application, especially in the top 5 cm. The amount of N returned to the soil by grazing was 71% and 57% in the sandy and the loamy soil, resp. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Global microbial necromass contribution to soil organic matter

2021 ◽  
Author(s):  
Yuan Liu ◽  
Jing Tian ◽  
Nianpeng He ◽  
Lisa Tiemann
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Health ◽  
Global Scale ◽  
Data Sets ◽  
Soil N ◽  
Distribution Maps ◽  
Spatially Resolved ◽  
Biogeochemical Models ◽  
First Time

Abstract Soil organic matter (SOM) plays an important role in mitigating climate change and sustaining soil health and food production 1,2. Mounting evidence suggests that microbial necromass is the main contributor to SOM 3; however, we lack quantification of microbial necromass at a global scale, especially in subsoils. Here, we generate, for the first time, global distribution maps of microbial necromass carbon (C) and nitrogen (N) and contributions to SOM in topsoil and subsoil. Globally, necromass concentrations varied widely across ecosystems and by latitude, contributing 19-60% to SOC and 41-92% to soil N stocks, with particularly large accumulations in boreal and tropical ecosystems. On average, fungal necromass contributions to SOM are 3x greater than bacterial, although this varied across ecosystems. Microbial necromass contributions to SOC are strongly associated with soil C:N ratios and pH; necromass contributions are greater in soils with narrow C:N ratios and higher pH. Microbial necromass is on average 23 and 77 times greater than living microbial biomass in topsoil and subsoil, respectively. These data highlight the importance of necromass contributions to SOM, especially soil N, and the need for spatially resolved necromass data sets that can be used in biogeochemical models to estimate SOM dynamics more accurately.

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