Die Bodenkultur - Journal for Land Management, Food and Environment
R. Steinwender, L. Gruber, A. Schauer, T. Guggenberger, J. Häusler and M. Sobotik:
Comparison of organic and conventional farming on a grassland farm
1st Communication: Grassland yield, forage feed value, amount of slurry
In order to characterize organic and conventional farming, a grassland farm with mowing pasture was divided into an organic (BE) and conventional (KE) experimental unit (forage and slurry were stored separately, cows were housed separately, Figure 1-2). The experimental groups differed in the treatment of slurry (aeration in BE), the level of fertilization (147 kg/ha mineral N in KE additionally to slurry), the method of weed control (only mechanical in BE) and the origin of the concentrate for the dairy cows (from organic farms in BE, Table 1). The objective of this 11 year experiment was to compare both farming systems in terms of grassland yield, nutrient content of the forage, feed intake, milk yield, health and fertility parameters of the animals, plus other essential parameters in the soil, slurry and the botanical composition of the pasture, as well as nutrient balances. This communication presents grassland yield, forage feed value and amounts of slurry. In group BE and KE, 5.51 and 4.36 ha were used, respectively (Table 2). Seven cows were kept in each group, resulting in a stocking rate of 1.27 and 1.60 cows per ha. The fertilization and feeding were based on the principles of organic farming and on experimental results from BAL Gumpenstein. The yield of hay and silage was determined by weighing, and the yield of pasture was estimated from the energy requirements of the animals and the energy content of the pasture.
The DM yield of the grassland presented in this paper (7,240 and 9,330 kg DM per ha in group BE and KE, respectively) is typical of this region. The yield of net energy and protein showed analogous differences as the DM yield (Table 3). Only small differences between the experimental groups were found in the nutrient and mineral content of forage. However, there were significant differences in crude protein and calcium in all three forages (hay, silage and fresh grass, Tables 4-6) between the experimental groups, which was partly due to the impact of the farming system on the botanical composition of the meadows.
There were significant differences in the slurry concentrations of nitrogen (4.5 vs, 5.2 g/kg), calcium (2.1 vs. 1.9 g/kg), % NH4-N in total N (31.6 vs. 39.3 %) and the pH value (7.67 vs. 7.40) for groups BE and KE, respectively. Only small differences were found for the other slurry components (Table 7). In summary, organic farming resulted in similar forage nutrient contents, but DM yield from the grassland was 2.000 kg/ha lower than with conventional farming due to lower N input. As a consequence the stocking rate and amount of slurry per hectare as well as the N content of slurry were also reduced.
Key words: Organic farming, grassland, forage yield, forage feed value, manure.