Estimated N leaching losses for organic and conventional farming in Denmark

The impact of organic compared to conventional farming practices on N leaching loss was studied for Danish mixed dairy and arable farms using an N balance approach based on representative data. On mixed dairy farms a simple N balance method was used to estimate N surplus and N leaching loss. On arable farms the simple N balance method was unreliable due to changes in the soil N pool. Consequently, the FASSET simulation model was used to estimate N surplus, N leaching loss and the changes in the soil N pool. The study found a lower N leaching loss from organic than conventional mixed dairy farms, primarily due to lower N inputs. On organic arable farms the soil N pool was increasing over years but the N leaching loss was comparable to conventional arable farms. The soil N pool was primarily increased by organic farming practices and incorporation of straw. The highest increase in the soil N pool was seen on soils with a low level of soil organic matter. The level of N leaching loss was dependent on soil type, the use of catch crops and the level of soil organic matter, whereas incorporation of straw had a minor effect. N leaching was highest on sandy soils with a high level of soil organic matter and no catch crops. The study stresses the importance of using representative data of organic and conventional farming practices in comparative studies of N leaching loss

Particulate Organic Matter as a Soil Quality Indicator of Sugarcane Plantations in East Java

This study is aimed to test the hypothesis that the soil quality of sugarcane plantations closely linked to the particulate organic matter (POM) and earthworm's populations. The research was conducted at five sites in Malang, East Java. The sites were selected based on differences in average annual rainfall and two types of soil management : with and without organic input. Soil samples taken from a depth of 0-20 cm were analyzed total organic C (TOC), total N, POM-C, and POM-N and earthworm's population density and biomass. The TOC were corrected by the clay content using pedotransfer equations so obtained TOCref. The interaction between differences in annual rainfall and two types of the treatments significantly (

Dutch (organic) agriculture, carbon sequestration and energy production

Carbon sequestration in soils is often mentioned in the discussions about climate changes. In this paper the opportunities for carbon sequestration in Dutch agriculture are discussed at farm and national level. Farm internal carbon sources are already completely used in livestock farming. The effect under arable conditions is limited in time and very limited compared to national CO2 emission. External sources are scarce. Energy production out of crop residues and manure via biogas installations is possible but the overall impact is again very limited. The effect of this biogas pathway on soil organic matter quantity and quality is not yet known. Organic arable farmers do already have a higher soil organic matter content than conventional farmers, partly due to external carbon sources. This puts them in a leading position. The disadvantage is that it is more difficult for them to do a next step in increasing soil organic matter

Comparisons of organic and conventional maize and tomato cropping systems from a long-term experiment in California

Yield differences and trends, organic matter accumulation, and the loss of nutrients to deeper soil horizons are discussed using data from organic and conventional maize/tomato cropping systems from the Long Term Research on Agricultural Systems Project (LTRAS) at the University of California, Davis. Compared to the conventional system, higher and increasing yields of tomatoes were observed in organic systems, but lower yields of maize. Fruit quality, measured as soluble solids, was not significantly different. Soil organic matter increased in the organic system, but remained stable in the conventional one. More irrigation water was used in the organic system than in the conventional one due to higher rates of infiltration, but less winter runoff occurred during the rainy season for the same reason. There was no measurable loss of inorganic N (NO3, NH4) in soil to 3 m depth in either the conventional or organic system after ten years of farming

Organic and conservation agriculture, the best of both worlds?

In millions of years huge amounts of organic matter were stored in the soil as organic matter or fossil energy carriers as oil, gas and coal. We make use of these stocks to supply us with energy and to be able to grow plants for our needs. However what has been stored in our soils for millions of years we now are depleting in a few hundred years. The amount of organic matter we return back to the soil is in general too low to maintain its capacity for plant production on the long term. Various studies show there is a decrease of organic matter in arable soils all over the world

Reducing soil degradation to increase resilience to climate change and strengthen livelihoods in Ethiopia.

Soil degradation is a major problem in Ethiopia. Depletion of soil organic matter is a cause of low agricultural productivity, as soils become less fertile and less resilient to extreme weather events, which are expected to increase with climate change. Further, this could increase the risk of crop failure and soil erosion, and soil carbon and nutrient losses. Low soil fertility is linked to poverty. Therefore, farmers need support to invest in soil conservation measures and to more effectively use organic resources, such as dung, to restore soils. If used effectively, such measures could be successful in addressing soil degradation

Agricultural practices shape microbial communities and change fresh and soil organic matter mineralization in a tropical soil : S11.07-P -1

Priming effect (PE) is defined as a stimulation of the mineralization of soil organic matter (SOM) due to fresh organic matter (FOM) supply. This process leads simultaneously to a loss of carbon to the atmosphere and to a remobilization of nutrients. PE should thus be considered in the management of residues or amendments in agricultural soils, especially where soil fertility is essentially based on organic supply. In Madagascar, the Direct-seeding Mulch based cropping (DMC) systems appeared to be an opportunity for the development of a sustainable upland rice culture. In DMC systems soil is not tilled and protected from physical erosion by dead or alive cover plants and/or mulches of crop residues. DMC systems are also known to increase soil organic matter stocks in the first centimetres below the mulch layer. As the quality of FOM is a determinant of the priming effect process, we were interested to evaluate whether the quality of mulches could shape the belowground microbial community and impact its capacity to mineralize SOM. In 2010, we sampled soil samples from a field experimentation set up in 2003 in the centre of Madagascar. The 10 first centimetres under three crop mulches (two grasses and one legume) and two different fertilizations (organic and organic + mineral), were sampled during the rice growing season. Soils were incubated in the presence of 13C-enriched wheat straw residue to measure their FOM and SOM mineralization capacity. Bacteria involved in both fluxes were identified by the coupling between DNA-SIP and pyrosequencing techniques. (Texte intégral

Microbial carbon mineralization in tropical lowland and montane forest soils of Peru

Climate change is affecting the amount and complexity of plant inputs to tropical forest soils. This is likely to influence the carbon (C) balance of these ecosystems by altering decomposition processes e.g., "positive priming effects" that accelerate soil organic matter mineralization. However, the mechanisms determining the magnitude of priming effects are poorly understood. We investigated potential mechanisms by adding (13)C labeled substrates, as surrogates of plant inputs, to soils from an elevation gradient of tropical lowland and montane forests. We hypothesized that priming effects would increase with elevation due to increasing microbial nitrogen limitation, and that microbial community composition would strongly influence the magnitude of priming effects. Quantifying the sources of respired C (substrate or soil organic matter) in response to substrate addition revealed no consistent patterns in priming effects with elevation. Instead we found that substrate quality (complexity and nitrogen content) was the dominant factor controlling priming effects. For example a nitrogenous substrate induced a large increase in soil organic matter mineralization whilst a complex C substrate caused negligible change. Differences in the functional capacity of specific microbial groups, rather than microbial community composition per se, were responsible for these substrate-driven differences in priming effects. Our findings suggest that the microbial pathways by which plant inputs and soil organic matter are mineralized are determined primarily by the quality of plant inputs and the functional capacity of microbial taxa, rather than the abiotic properties of the soil. Changes in the complexity and stoichiometry of plant inputs to soil in response to climate change may therefore be important in regulating soil C dynamics in tropical forest soils.This study was financed by the UK Natural Environment Research Council (NERC) grant NE/G018278/1 and is a product of the Andes Biodiversity and Ecosystem Research Group consortium (www.andesconservation.org); Patrick Meir was also supported by ARC FT110100457

Effect of Irrigation Interval and Soil Amendments on Soil Organic C, Nitrogen and Potassium of Sandy Soil and Growth of Jatropha Curcas L.

Inherently, sandy soil is the unfertile soil with low in all aspects of soil fertility and has a low capacity to retain water applied nutrients. To improve the fertility of sandy soil as media growth of Jatropha curcas, clay and organic matter may have important role when they are incorporated to the sandy soil. This study investigated the effect of irrigation interval and incorporation of clay together with organic matter to sandy soil on soil organic C, N, and K and growth of J. curcas. The rates of clay and organic matter incorporated to top sandy soil were 5% clay + 0.8% organic matter and 10% clay + 1.6% organic matter. Two irrigation intervals tested were 10 day and 20 day. The results found that incorporation of 10% clay + 1.6% organic matter to sandy soil increased soil C organic, N total and exchangeable K which in turn increased number of leaves and number of lateral branches of J curcas. Irrigation intervals had no effect on all parameters observed

Efficiency Strategy of Organic Matter Use for Soil Fertility and Productivity by Soil Biology Resources Empowerment

Indonesia is an archipelago in wet tropical volcanic regions have high soil biodiversity, high rate of weathering and high of soil erosion, but low on soil fertility and soil organic matter content. Improvement of soil fertility to plant directly with the provision of organic materials requires a large amount and expensive. Problems faced by low organic matter production ability, high decomposition rate, bulky and is in the archipelago, making it difficult in the procurement and conservation of organic matter in soil and expensive transportation costs. Provision of organic materials with the aim of empowering the soil biology resources to enhance soil fertility potential pursued. In addition to the dose of organic matters required is relatively lower may also prevent the emergence of soil born diseases are also increasing of soil organic matter conservation. In determining land suitability evaluation in wet tropical volcanic region should consider the role of soil organism populations to support crop production and protected soil organic matter content