"Champions League" of grassland fertilization

Quelle: Landwirtschaftkammer OÖ

Gülleseparierung plus Ausbringung mittels Schleppschuh!

Cattle manure is a valuable and highly effective complete fertilizer in the circular economy.

Farmyard manures, such as slurry, manure, and liquid manure, which inevitably arise from livestock farming, must be returned to agricultural land in the spirit of a circular economy. Farmyard manures are extremely valuable complex fertilizers that require careful handling. Only with optimal farmyard manure management (consistency, application rate, timing of the year, weather, temperature, precipitation, technology) can optimal grassland and field forage yields of the highest possible quality be achieved without excessive mineral supplementation.

1. Separation

For many farms, separating cattle manure is a better solution than diluting it with water.

Dilution of cattle manure (water or separation)
In order to be able to use cattle manure, which almost always has a much too thick consistency, efficiently in terms of nitrogen effect without taking into account any application technology, a corresponding dilution of at least 1:1 with water or separation is recommended.

If the slurry is too thick, it sticks to the crop, sits on top, and is highly susceptible to ammonia losses. The slurry solids are then lifted up with the grassland growth and harvested during the subsequent cut. This can significantly contribute to contamination and thus negatively impact forage quality. Regarding the risk of contamination, there is essentially no difference between applying thick slurry close to the ground using a trailing hose or spreading it over a wide area.

Manure separation is the way of the future for most farms
However, upon closer examination, it is increasingly becoming clear that although high dilution with water can increase infiltration and thus significantly reduce ammonia emissions (UNECE drag hose factor minus 30%), the solids remain in the slurry, and the risk of feed contamination still exists. This can only be resolved through slurry separation.

Furthermore, a dilution ratio of at least 1:1 with water results in double the application rate and thus double the application costs. Therefore, this option is only economically viable for largely consolidated farms. It should also be considered that many farms do not have the water available for sufficient dilution. Over the winter, the manure is stored largely undiluted due to available storage capacity. Manure dilution is therefore usually carried out by discharging roof and surface water after the first application during the growing season. However, the recent frequent dry years have shown that the rainfall absolutely necessary for manure dilution is not available.

Therefore, it turns out that manure separation is the better way if the framework conditions are right (ÖPUL, Invest).
Nutrient distribution of manure separation
As part of the Slurry Conference held at the end of August in Handenberg, Braunau District, a slurry separation trial including analysis was conducted. 14 cubic meters of cattle slurry with a dry matter content of 7.2% were separated. From the initial volume, 3.58 cubic meters of loose solids separation with a dry matter content of 28.5% were obtained. The thin separation is estimated to have a 10% volume reduction (literature data range between 7 and 15%) and has a dry matter content of 4.2%.

Cattle slurry separation - Slurry Conference Braunau - July 13, 2021

*10% estimated volume reduction

The table shows that the N, NH4, P2O5, and K2O contents of the thin slurry separated change only slightly compared to the original slurry. The solid slurry separated has a slightly higher phosphorus content. This result is largely consistent with the literature, although there are some fluctuations.

Legal framework for manure separation

Costs of manure separation

Manure separation is both labor-intensive and costly. According to Alfred Pöllinger, HBLFA Raumberg-Gumpenstein, the costs for the average Austrian cattle farm range between €2.50 and €4.50 per cubic meter of manure. These considerable costs can be reduced through cooperation (machine rings, machine pools) and the use of the solids separation as bedding, while adhering to best practice recommendations.

Further details can be found in the newly published ÖAG brochure 06/2021 “Slurry Separation – Technology, Application, Economics and Effects”.

The expensive technology is supported

2. drag shoe

The application of separated slurry in strips close to the ground using a trailing shoe offers the most advantages for grassland and field forage.

If thin slurry is available on the cattle farm, it is also suitable for improved, low-lying, strip-like spreading techniques. The trailing shoe technology is increasingly proving to be the most suitable for growing crops in general (e.g., winter cereals, etc.) and for grassland and field forage in particular. When spreading using a deflector plate, it is essential that the slurry is spread immediately after each cut to ensure it reaches the soil and not the plants. For many dairy farms, this often represents an extreme peak in workload, especially when the weather is unsuitable. And this is usually unsuitable: in wet soil conditions, heavy slurry technology has a particularly high risk of compaction, sunny periods are unsuitable due to the high risk of emissions, and only a limited amount of slurry can be spread immediately before rainfall.

Slurry spreading using a trailing shoe can significantly reduce this peak workload ("loader wagon off - slurry tanker on"). This is because you can wait to spread slurry until a suitable time arises. The grassland or field forage growth should have grown at least 10 to 15 centimeters. The trailing shoe glides over the soil surface, dividing the crop so that a large portion of the slurry is deposited directly onto the soil surface and not onto the plants. Some techniques are designed so that the contact pressure creates a shallow slit to facilitate the rapid infiltration of the liquid phase of the slurry into the soil. At the same time, the shading effect of the crop closing again after spreading further reduces the emission activity of the slurry. This allows the fast-acting ammonium nitrogen to be optimally converted into yield with the highest possible crude protein content. The solid organic portion of the slurry remains close to the soil. This minimizes the risk of forage contamination with a recommended cutting height of at least 7 centimeters during subsequent growth and with optimal harvesting equipment settings.

Considering emissions and forage contamination, slurry injection or slotting is the best option. However, this has certain disadvantages due to the narrower working width, the even higher weight, the potential for turf damage, and the higher costs. Therefore, slurry application using a trailing shoe for grassland and field forage is the preferred method.
Ground-level application is the key measure for meeting the ammonia reduction targets
Only through the widest possible application of manure spreading using trailing shoe technology in cattle farming can the requirements of the EU NEC Directive for reducing ammonia emissions – which are classified as air pollutants – be met by applying a reduction factor of minus 50%. If expensive measures are implemented to reduce ammonia losses in the barn and storage area, the nitrogen content per cubic meter of manure would have to increase. However, if this manure is then spread using conventional wide-area spreaders, a higher proportion of ammonia will simply be lost as exhaust gases. Only with improved application technology can the circle of minimizing ammonia losses in the manure chain from barn to storage area to application be closed.

ÖPUL and investment support
For 2021 and 2022, the entry ban for the ÖPUL measure "near-soil application" has been lifted, the minimum application rate per farm has been abolished, and the cubic meter limit has been raised from 30 to 50 cubic meters per hectare of fertilizable arable and grassland land. In addition, the funding rate for near-soil application technology and manure separators has been increased from 20% to 40% in the investment subsidy. The new LE 23+ discusses and calls for an adjustment of the compensation for the ÖPUL measure "near-soil application of liquid farm manure and biogas manure."

Given the farm structure in Austria, these technical solutions, which are costly for agriculture, cannot be financed without public support. The course has been set for the best possible implementation of these necessary measures. All farms with relevant manure quantities and suitable land are now being called upon to take advantage of these offers. Information is available from the Soil.Water.Protection.Consultancy (050/6902-1426). www.bwsb.at.