This thematic newsletter presents the most important research results by ILVO and several partners on the subject of sustainable soil management, management of nutrients and organic matter, composting and use of compost. These results were presented during the CriNglooP Collective on October 9, 2014.
Phosphorus in agricultural soils: a long-term effort
Phosphorus is an essential nutrient for crops, but too much phosphorus fertilisation can lead to eutrophication of surface waters. An ILVO literature study on the phosphorus cycle in soils reveals that changing the soil phosphorus (P) content will take a long time. Reducing P fertilisation does not result in a short-term decrease of phosphorus concentrations in water bodies. For soils with a P high level, lower P fertilisation has no effect on crop performance.
Phosphorus leaching and the effects of long term application of several fertiliser types
Which fertiliser types have the largest potential to increase the soil organic carbon level, without further increasing phosphorus losses through leaching? Observation of long term field trials in Flanders and the Netherlands, revealed that in soils with a large soil P content, compost seems to be the best option.
Do the nitrogen fertilisation standards imposed by the European nitrates directive achieve their goal?
Limits to nitrogen fertilisation must be imposed to comply with the concentration level set by the European Nitrates Directive. The relationship between the amount of fertilisation and nitrate losses to ground- and surface waters depends on the fertilisation dose, crop type, harvest time and whether or not a catch crop is sown. Based on nitrogen fertilisation experiments, we could evaluate the effect of different amounts of effective nitrogen on yield and potential nitrogen losses. We assessed the effectiveness of current effective N fertilisation standards and made suggestions for further refinement.
A deep-rooted problem. Soil condition, depth of rooting and time of sampling: a study of how and when catch crops capture mineral nitrogen
Catch crops such as white mustard and Italian ryegrass can draw mineral nitrogen from deeper soil layers to the surface, thus preventing nitrate leaching. But do all catch crops do this equally well under all circumstances? Is there an optimal moment for taking nitrate residue samples? ILVO has studied the efficiency of catch crops and the impact of soil condition and root characteristics during field trials.
Soil and ecosystem services
A critical look at the effect of compost and crop rotation. Do farm compost application and crop rotation actually improve soil quality and crop yields?
The repeated application of farm compost resulted in a clear improvement of soil quality. Crop rotation effects on soil properties were not fully expressed after five years. Higher yields were mainly detected at low N-fertiliser levels.
Intensive vegetable growing based on compost amendment and non-inversion soil tillage is feasible
Adverse effects of intensive tillage and fertilization practices in vegetable cropping systems may be counteracted by compost application and reduced tillage. Experiments with these techniques on a farmer’s field with broccoli, carrots and leek have shown that compost application and reduced tillage can sustain soil quality, without an immediate need to adapt nitrogen fertilization and without yield losses!
Playing the field. Which combinations of compost application, slurry type and soil tillage yield the best results for crop yield, disease suppression and soil quality?
During the BOPACT field trial, ILVO is investigating the longer term effect of soil improving measures (compost addition and non-inversion tillage) on soil quality, crop yield and disease suppression for two major fertilisation systems in Flanders: fertilisation based on cattle slurry vs fertilisation based on pig slurry. Thus far, clear treatment effects on soil quality have been observed, such as the effect of non-inversion tillage on soil organic carbon distribution, soil microbial biomass and aggregate stability. Further research is needed.
Could adding biochar improve soil quality while combatting climate change?
Can biochar sequester carbon in soil while improving soil quality in temperate regions like Flanders? Biochar is the stable, carbon-rich product obtained when organic residues or organic waste products are pyrolysed (thermally decomposed under low-oxygen conditions). Applying biochar to soil could improve soil quality and increase crop yield. Possible additional benefits are long-term carbon sequestration and a reduction of soil greenhouse gas emissions, which is positive for climate change mitigation. Results of the biochar types tested showed short-term effects on soil processes but little mid-term effects on soil quality. Future research includes observation of long-term effects of biochar amendments in a field trial and study of biochar in compost.
Non-inversion tillage and green manures in organic cropping systems
Non-inversion tillage and the use of green manures can guarantee good crop productions when soil compaction is counteracted and green manures are properly destructed. This was shown by research results from ILVO and Inagro based on results from a multiyear experiment with grass-clover as green manure crop.
Healthy soil - healthy plants (without pesticides). Soil management goes hand in hand with natural disease and pest control.
Does good soil quality lead to increased natural disease suppression of crops? Which soil properties are determining factors for disease suppression and how can we influence these properties? How can state-of-the-art techniques contribute to a more accurate characterisation of soil biology?
Soil management for the future. Best management practices for sustainable soil management: what can we learn from the outcome of European long-term field experiments?
Results from European long-term field trials indicate that both the adoption of non-inversion tillage and compost application clearly enhance soil quality without causing substantial crop losses.
Breaking down barriers to building up the soil. Why are some farmers reluctant to use good soil management practices?
Good agricultural practices that prevent soil quality deterioration are not used sufficiently in practice. ILVO wants to know why. ILVO researchers surveyed Flemish farmers to identify which social, economic, legislative, and biophysical barriers might hinder their choice to apply these practices. The experiences and motivations of farmers who do and do not choose to farm in this way were also compared.
Serving leftovers to the soil. Will soils degrade when crop residues and energy crops are removed for energy production?
Removing crop residues and growing energy crops for the production of second-generation renewable energy is not necessarily bad for soil carbon content, according to recent research by ILVO, Inagro, KBIVB and VITO. If only a portion of the crop residues are removed, for instance, or if perennial energy crops are grown, soil quality does not have to suffer. Furthermore, energy production generates carbon-rich waste streams that could be used as soil improvers or organic fertilizers. Agriculture may be evolving away from the direct input of crop residues toward a more complex model where a portion of the removed carbon and nutrients are returned to the soil after processing.
Getting to the root of the matter. Would removing roots influence the stable organic matter in soils?
Crop residues from grain maize or other crops could be a potentially useful resource for other uses such as renewable energy production. Removing these residues, however, also removes their organic matter and the nutrients derived from these residues are also removed from the soil. ILVO investigates the consequences of removing crop residues on the buildup of the stable organic matter pool in the soil.
Up with nature, down with farming? Searching for balance between ecological objectives, ecosystem services and economic feasibility for the farmer
Via a field campaign, literature studies, interviews and logbooks, ILVO aims to estimate the effect of nature oriented measures that are implemented on agricultural land. This effect is expressed in terms of biodiversity, ecosystem services, farm income and logistics. More than 12% of the land in Flanders belongs to the Natura 2000 network, where people strive for nature conservation and ending the loss of biodiversity. To reach this objective, target habitats must be created and the environmental pressure of human activities must be reduced – which will have a considerable socio-economic impact on the agricultural sector. This research should therefore contribute to a cost-effective implementation of these measures.
Composting and manure processing
Sustainable soilles strawberry culture is ripe for the picking. Compost in growth substrates is good for strawberry, but only with correct fertigation.
Adding compost to growth substrates has potential to increase the sustainability of soilless strawberry culture. Research by the Flemish practical research centre for horticulture (PCH) and ILVO revealed that strawberry plants make highly efficient use of the phosphorus and potassium in the compost, and that compost addition results in reduced export of nutrients via drain water and spent substrate. Compost may also increase the disease resistance of strawberry. The natural variation in different composts poses challenges to correctly adapt the fertigation and thus control the nutrient supply.
Composting byproducts in Flemish agriculture and horticulture
One of the four cases of the GeNeSys project at ILVO studies the potential of composting byproducts from agriculture as a valorisation pathway. Compost application improves soil quality and fertility, a prerequisite for biomass production. On-farm composting of agricultural byproducts closes nutrient and material cycles are locally. Before these benefits can be realised, however, a few hindrances need to be removed.
Composting and ensiling to optimise storage and processing of solid cattle manure
In the context of the Manure Decree and the Natura 2000 implementation (PAS; focus on reducing nitrogen emissions), ILVO is investigating whether the storage and processing of solid cattle manure could be optimised to reduce nutrient losses and obtain high-quality fertiliser. Are composting and ensiling appropriate techniques? ILVO investigated in the lab as well as in the field.