Circular agriculture is a theme that plays an important role in the strategy of the Ministry of Agriculture. Many farmers struggle with the question of how the cycle can be shaped at farm level. The use of residual flows is obvious and is already being applied. The nutrients from the residual flows such as animal manure and compost can partly replace artificial fertilizer.
The supply of organic matter has positive effects on the soil structure. Organic fertilizers have certain advantages over artificial fertilizers, not only in agronomic areas. From a business perspective, profits can be achieved by partly replacing artificial fertilizer with organic manure. Especially now fertilizer prices is on the rise, it is worthwhile to use alternatives where possible.
Broad research
BO Arable Farming has the following fertilizers examined: cattle and pig manure, solid cattle and goat manure, solid pig manure, poultry manure, organic lime fertilizer, vegetable digestate, unprocessed and ensiled roadside and ditch clippings, compost, straw, processed animal protein, humic acids, seed meal and seaweed preparations. In addition to the effects of the application of organic fertilizers on the build-up of effective organic matter (EOS) and the supply of nitrogen, phosphate and potassium, the effects on soil life and disease resistance have also been investigated.
The risks included in the study are the danger of nitrate leaching and the introduction of contaminants. These can be plant pathogens and weed seeds, but also physical (glass, plastic, etc.) and chemical contaminants.
According to the researchers, the main effect of animal manure is the supply of minerals. Although most products also have a positive effect on the build-up of EOS. With liquid manure and digestate there is a real risk of nitrate leaching. This can be overcome by applying this fertilizer to a growing crop. The crop then absorbs the nitrogen before it can be flushed out. Due to the strict phosphate standards in the Netherlands, pig and poultry manure has limited applicability.
Not everything is suitable
Roadside and ditch clippings have a major effect on the build-up of EOS. It just has one major disadvantage. The clippings are generally contaminated. They often contain weeds and waste. In addition, it cannot be ruled out that it stimulates soil pathogens.
Processed animal protein and seed meal should have a positive effect on the disease-resistant capacity of the soil. The research found interesting effects against certain soil pathogens. However, the variation is too great for a reliable application. In addition, these products are (still) too expensive for profitable use.