Production potential of winter and spring mixtures of field pea and oats in Serbia

Field pea and oats are two forage crops that combine very well in mixtures, both in terms of sowing and cultivation as well as yield and forage quality. The mixture is characterized by a short vegetation period, a positive effect on the soil and good resistance to weeds, diseases and lodging. In multi-year trials on the experimental fields of the Institute for Animal Husbandry in Belgrade, mixtures of oats and field pea were grown in both winter and spring sowing. The winter sowing trials included three varieties (domestic Kosmaj, OS Adam and OS Letin from Croatia) and their mixtures (100% pea:10% oats; 100% pea:20% oats) for each variety, composed using the additive method, along with four control plots (pure stands of each variety). At spring sowing, the following factors were investigated: nitrogen fertilization (0, 40 and 80 kg ha⁻¹), the sowing ratio of the NS Junior variety and oats in mixtures (100:15% and 100:30%) with two control plots (pure field pea and pure oats) and the optimum harvest time (full flowering and pod formation in the field pea). The varieties Kosmaj (21.5 t ha⁻¹) and Adam (27.9 t ha⁻¹) achieved the highest yield of fresh biomass in winter sowing, while the leafless variety Letin had the lowest yield (12.8 t ha⁻¹), both individually and in mixtures. The average yield of fresh biomass was significantly higher in the 100:20% pea: oats mixture than in the 100:10% mixture and in the pure crop. The dry matter yield was also highest in the 100:20% mixture, although not significantly higher than in the 100:10% mixture and the pure crop. The leafy varieties OS Adam (164 g kg⁻¹) and Kosmaj (153 g kg⁻¹) achieved higher protein contents than the variety Letin (136 g kg⁻¹). Based on these analyzed values and the low competitiveness of oats in winter mixtures with peas, the ratio of these two species should not be less than 100:20% at sowing. In spring sowing, nitrogen fertilization and the different seeding rates had a significant influence on biomass, hay and crude protein yields. On average, the highest hay yields were achieved with 80 kg N ha⁻¹ (4.96 t ha⁻¹), followed by 40 kg N ha⁻¹ (4.27 t ha⁻¹). The highest protein yields were achieved with 40 kg N ha⁻¹ (704 kg ha⁻¹), followed by 80 kg N ha⁻¹ (638 kg ha⁻¹). On average, the 100:30% mixture had a higher hay yield (4.82 t ha⁻¹) and lower crude protein yield (693 kg ha⁻¹) compared to the 100:15% mixture (4.44 t ha⁻¹ and 730 kg ha⁻¹, respectively). Nitrogen fertilization did not lead to a significant increase in costs, but it increased the net profit by 163%, depending on the nitrogen levels and composition of the mixture. Nitrogen fertilization also achieved greater economic efficiency in the 100:15% mixture compared to the 100:30% mixture. Mixtures of field pea and oats perform better than pure crops and provide economical forage in a short time. The use of optimal seed ratios and nitrogen fertilization can significantly increase the productivity and profitability of ruminant forage with minimal impact on overall production costs.