Manure usage has multiple benefits – but how to get started?

The positive effect of manure use on soil structure and microbial activity has increasingly been included in the manure discussion. It also interests people, which could be seen when the webinar about manure usage, organized by Carbon Action and the SuMaNu project on January 12, gathered nearly 150 listeners.

As a result of the segregation of animal and crop farms, many crop farms may have had break in manure usage lasting years or even a generation. However, planned and efficient use of manure is an advantage for the soil, climate and water bodies. Long-term improvement of soil quality increases yield and thus, it is also an advantage for the farmer’s purse.

The characteristics of the manure and the nutrients it contains vary depending on the production animals, used feed and also whether what is referred as ‘manure’ is actually slurry, bedding manure or urine, or combination of these. Anyhow, the amount of manure produced each year in Finland contains so much nutrients, that it would cover the entire need for mineral phosphorus in the country, and half the need for mineral nitrogen. Phosphorus in manure is in a form that is perfectly usable for plants, but nitrogen is in a less soluble form. Thus, when using manure as an only fertilizer, there can be a need to nitrogen supplementation, since the limits of fertilization are most often calculated from the amount of phosphorus.

Manure use improves soil quality. Picture: BSAG

Manure provides the soil with nutrients and organic matter and thus sustains microbial life. The organic matter buffers the soil against acidification and creates stabile aggregate structure. The better the structure, the better the resilience of the soil against water erosion and soil compaction. The stability of soil aggregate structure is good against slaking and reduces the risk of crust formation. Clay soils require a lot of organic matter to keep the soil aggregate structure stabile. In coarse mineral soils, increasing the amount of organic matter in the field improves nutrient and water storage capacity. Compared to the use of mineral fertilizers, manure has a positive effect on the amount of organic carbon in the soil.

The benefits of manure are manifold, but as a product, it is geographically unevenly distributed. Long transport distances would require further processing of manure, but livestock and crop farms located close to each other could benefit from more cooperation. The first step for the receiving farm to do is to choose the most desired effect: fertilization or improving soil health and structure.

Analysis of the nutrient content of manure is important for knowing the fertilization effect, but also to follow manure regulations, which emphasize minimizing nitrogen emissions. The following practical steps are to find out who has an excess of manure, what would be a suitable amount for the field in question, how and when manure could be applied, and by whom. In addition, the risks posed by the spreading of common wild oat, different weeds, and odor nuisances must be weighed. It must also be remembered that the intensity of field tillage plays a major role in the improvement of soil quality and controlling leakage. From this point of view, too, the objectives for manure use must be carefully considered and the use of manure must be optimally adapted to the crop rotation in each plot. However, manure application can be started with one plot at a time. For example, at the end of fallow in late summer, when the carrying capacity of the field is at its best and contractors have the most time.

Experienced contractors are able to avoid field compaction by keeping tire pressures low and designing application lines efficiently. A particularly gentle method of manure application is traction hose application, which substantially reduces the weight on the soil. With suction hoses, the field can be reached already in early spring. Thus, the fertilizer is applied when the plants make the best use of it. Traction hose spreading is best suited for farms with large fields near to each other. The method can be used to apply all kinds of slurry and to grass, seedlings and to bare ground.

The presentations (in Finnish) given at the manure webinar can be found here.