Impacto da arborização e adubação nitrogenada na produção de grãos, forragem, animal e lucro de distintos sistemas integrados

Abstract

In southern Brazil, in winter, there are few viable economic options for agricultural crops, consequently many areas of summer crops did not generate income during this period. Similarly, forage species such as black oats (Avena strigosa Schreb.), white oats (Avena sativa L.) and ryegrass (Lolium multiflorum Lam.) have good yields in winter, so integrated agricultural production systems (SIPA) can assist in the continuous use of agricultural areas, making them productive throughout the year and improving soil quality over time. Most of the forage and grain species present good performance against nitrogen fertilization, however, this input can represent a large part of the costs of the activity. One of the advantages of SIPA is to reduce dependence on external inputs, which may, in the case of winter forage fertilization, reduce the cost of leaving it in the successor crop. Although the inclusion of the tree component in SIPA brings benefits to the system, it is important to pay attention to the tree characteristics in order to prevent them from suffering damage to the animals and having their value reduced. The objective of the present study was to analyze grain ewe productivity, animal performance and the profitability of such activities in different LPIS, that is, with or without Eucalyptus grandis trees, under different N doses, during three consecutive winters (2020, 2021 and 2022), right after planting the trees. The present study was carried out at the Fazenda Modelo Research Station of the Instituto de Desenvolvimento Rural do Paraná IAPAR-Emater (IDR - Paraná). The area was divided into 12 experimental units, 6 of which were wooded. The experimental design was randomized blocks with three replications and four treatments arranged in a 2 x 2 factorial scheme, presence of trees (ILPF) and absence of trees (ILP) and two doses of nitrogen fertilization in coverage: 20 vs. 60 kg of N/ha for the grain oat IPR Artemis, cultivated in 2020 and 2021, and 50 x 150 kg of N/ha for the black oat (IPR 61) + ryegrass (BRS Ponteio) pasture implemented in 2022. grazing by Purunã heifers, with an average initial age of 15 months, was continuous with variable load in order to maintain pasture height around 20 cm. The animal performance variables showed significant differences (P<0.05) in relation to the systems, and in the ILP treatment a higher average daily gain (0.798 ± 0.0629 kg/animal/day), greater gain per area (602 ± 120.0 kg LW/ha in 139 days) and higher load (1142 ± 148.3 kg LW/ha) than in the ILPF system (0.641 ± 0.0274 kg/animal/day; 378 ± 39.73 kg PV/ha; 868 ± 85.8) respectively in 139 days). No significant differences were observed for these variables regarding nitrogen doses. All trees suffered at least one type of damage from the animal, with 89.3% of the trees accumulating lesions of type Cl (bark lesion without reaching the wood), Dl (lesion greater than 5 cm in diameter) and Tl (lesion lesion). trunk reaching the wood by removing the cambial tissue), resulting in a score of 6.5 and classifying it in the High damage intensity class. The diameter of the evaluated trees showed a significant linear relationship with the incidence of damage. The production of oats varied between 1712 ± 382.1 kg/ha in the year in 2020 and 3617 ± 706.3 kg/ha in 2021. Regarding the economic evaluation, in general, the treatments had losses with the production of oat grains due to low yield and low winter market prices. For animal production, the most profitable system was the ILP with 50 kg N/ha (R$ 3,644/ha). An increase in N level reduced profit (-53% in CLI and -156% in CLIF) for both oat grain and livestock production, regardless of LPIS type. It is not worth raising the N dose by 150 kg/ha, as this did not effect the production of oats and cattle in the present study, negatively influencing

the profit of the experimental units that received such treatment. The integration of cattle from the first winter, after tree planting, through the use of physical barriers, such as fences around immature trees, can be a more profitable alternative than the production of oat grains.