Atributos do solo e do sistema radicular em distintos sistemas de produção de forragem

Abstract

High proportion of the food consumed comes from the soil, however, 1/3 of the world's soils are already degraded. The objective was to evaluate soil and root system attributes in different forage production systems. The experiments were carried out at the Experimental Stations of the Agronomic Institute of Pernambuco (IPA) located at Itambé, in the North Forest Zone of Pernambuco State and at Arcoverde, in the Sertão region of the State. At Itambé, the experiment was installed in April 2011 and the experimental treatments consisted of i) intercropped pastures Urochloa decumbens (Stapf) R. D. Webster (braquiária) + Mimosa caesalpiniifolia Benth. (sabiá) (B+S) and ii) braquiária + [Gliricidia sepium (Jacq.) Steud.] (gliricídia) (B+G) in a randomized complete block design, with three replications. Soil samples were collected at two distances from the legumes, being 0 m away from the double rows of legumes (WR) and 8 m away from the double rows of legumes (BR), in the month of October 2019 to analysis of roots stock, soil physics and chemical analyzes at 0-10, 10-20, 20-40, 40-60, 60-80, 80-100 and 100-120 cm depths; physical fractionation of soil organic matter (SOM) at 0-20 and 20-40 cm depth and soil microbial biomass carbon (SMBC) and nitrogen (SMBN) content at 0-20 cm depth. In Arcoverde, the cultivar evaluated in two experiments (I and II) was forage cactus (Opuntia stricta Haw. Cv. ‘Orelha de Elefante Mexicana’) and the experiments were established in June (rainy season) 2011. In experiment I, the experimental design was split-plot in a randomized complete block design, where the main plot was formed by different planting density and the subplots, by the factorial arrangement between frequency, and harvest intensity. While in experiment II, the experimental design was in split-split-plot in a randomized complete blocks, in which the main plots were formed by different doses of organic fertilization, the subplots by different doses of N fertilization and the sub-subplots, harvest frequency of forage cactus, in four experimental blocks. In both experiments (I and II), samples were collected to analysis of roots stock, soil physics and chemical analyzes at 0-10 and 10-20 cm depths and physical fractionation of soil organic matter (SOM) at 0-10 cm depth. Sample collections for experimental analyzes in experiments I and II were carried out in August 2019, but for roots stock and soil bulk density (BD) analyzes also took place in September 2021. In the Experiment at Itambé, the roots stock along the edaphic profile (0-120 cm), being 22.96 t ha-1 at the sampling site WR and 11.97 t ha-1 in 8 m away in BR in treatment B+G and 22.61 t ha-1 WR and 11.06 t ha-1 BR in treatment B+S highlights the importance of grass and forage legumes for the benefits of edaphic attributes in silvopastoral systems. In the Experiment I at Arcoverde, there were no significant effects in relation to the roots stock at 0-10 and 10-20 cm depth, being the experimental mean values 12.45 t ha-1 and 6.06 t ha-1, respectively, nor for the soil BD at this greater depth (p>0.05) whose mean value was 1.28 g cm-3. In the Experiment II at Arcoverde, the experimental soil BD was below the critical limit. Organic and nitrogen fertilization of at least 10 t ha-1 year-1 and 120 kg ha-1 year-1, respectively, and biennial harvest frequency contribute to higher roots stocks of forage cactus Orelha de Elefante Mexicana at depth 0-10 cm.