Cultivo de sorgo granífero sobre diferentes coberturas em cultivo isolado e consorciadas no Cerrado mineiro em diferentes épocas de plantio

Abstract

Sorghum is a widely cultivated crop for both grain production and forage during the off-season in the Brazilian Cerrado due to its hardiness, drought tolerance, high nitrogen use efficiency, good adaptability to different soil types, and lower production cost. It is generally planted in a no-till system over the residues of the previous crop. However, it is rarely cultivated over a previously formed mulch for its cultivation in consecutive cycles. The objective of this study was to evaluate the production, decomposition, and nutrient cycling of cover crop residues in isolated and intercropped cultivations, as well as their relationships with grain sorghum production in two consecutive cycles. The experiment was set up in a randomized block design, where seven types of soil cover were evaluated: 1- Brachiaria (B); 2- Millet (M); 3- Crotalaria ochroleuca (CO); 4- Intercropping 1 (MIX 1): Buckwheat, Crotalaria ochroleuca, millet, C. breviflora, Brachiaria, Coracana grass, and Crambe; 5- Intercropping 2 (MIX 2): Buckwheat, C. ochroleuca, C. breviflora, Coracana grass, Crambe, and Brachiaria; 6 - Intercropping 3 (MIX 3): Brachiaria, Coracana grass, millet, forage sorghum, cowpea, and pigeon pea, all with four replications. The production of fresh (FM) and dry (DM) matter, decomposition, half-life (T1/2 life), and nutrient cycling of the residues were evaluated, as well as the agronomic parameters and productivity of grain sorghum in two consecutive cycles. In the first cycle, it was observed that in the isolated cultivation, MIX 2 presented higher DM production, greater accumulation and cycling of nutrients, and lower decomposition rate and half-life of its residues. In the intercropped cultivations, MIX 2 presented DM production similar to that of MIX 1 and MIX 3, greater accumulation and cycling of nutrients, higher decomposition rate, and lower half-life of its residues compared to MIX 1 and 3. The highest residue decomposition rate occurred in the isolated cultivation and in MIX 2, where the plant was present with two species (C. ochroleuca and C. breviflora). Regarding the half-life (T1/2) of nutrient release, the following increasing order was observed: Mg < K < Ca < N < P < S. The lowest values for fresh and dry mass of grain and panicle, as well as grain yield of grain sorghum, occurred when it was grown on MIX 1. The cover crops used did not influence the agronomic parameters: number of panicles, plant height, panicle insertion height, and basal stem diameter.