Desempenho de genótipos de sorgo para corte e pastejo plantados em safra e safrinha

Abstract

The development of new forage options that present a balance between productive and nutritional characteristics is fundamental for the sustainable development of Brazilian agriculture. This study aimed to evaluate the agronomic characteristics of 30 and the nutritional characteristics of 15 sorghum genotypes for cutting and grazing planted in normal season and off-season and to select the best hybrids for use in animal feed. The genotypes were planted at Embrapa Cerrados-DF on 12/20/2017 and 02/05/2018. The experimental plot consisted of double lines spaced 0.50 m apart, five meters long and with a floor area of three meters. The experiment was carried out in a completely randomized design in a 30X2 factorial arrangement, with 30 genotypes in two planting seasons (for the agronomic variables) and 15x2, with 15 genotypes in two planting seasons (for the nutritional variables), and with three replications. The data obtained were submitted to analysis of variance (Two Way ANOVA), with Scott-Knott clustering for genotype means (p<0.05) and Fisher's test for planting season means (p<0.05). The total natural matter and dry matter yields were higher in the normal season compared to the off-season (p<0.05) and varied between 25,148 and 58,987 kg ha-1 and 3,579 and 7,148 kg ha-1, respectively. Plant heights ranged from 116 to 160 cm in the normal season and from 112 to 153 cm in the off-season (p<0.05). The number of tillers ranged from 365,185 to 898,518 tillers ha-1 in the normal season and 248,333 to 586,666 tillers ha-1 in the off-season (p<0.05). The proportion of leaf in dry matter of the genotypes varied (p<0.05) between 41.1 and 55.9 % in the normal season and 40.1 to 55.9 % in the off-season. Genotype densities were higher (p<0.05) in the normal season and varied (p<0.05) from 10.9 to 18.2 kg DM cm2(-1) between genotypes (p<0.05). The best genotypes considering agronomic characteristics were 16F24008, 16F24007, 16F26007, 16F26014 and 16F26008. The average DM contents were 18.4% in leaves, 10.0% in stems and 11.3% in whole plants. The average CP content in the leaves was 18.1%, in the stems 8.5% and in the whole plants 11.6%. The average CP yields were 818.4 kg ha-1 in the normal season and 437.1 kg ha-1 in the off-season. The average NDF contents were 64.3, 63 and 63.9 % in leaves, stems and whole plants, respectively. Lignin contents were, respectively, 2.0, 4.1 and 2.8% in leaves, stems and whole plants. The average IVDM was 66.3% in leaves, 57.0% in stems and 63.3% in whole plants. The digestible dry matter yields were 4,534.1 kg ha-1 in the normal season and 2,356 kg ha-1 in the off-season. In general, the nutritive values were higher in the harvest in relation to the off-season due to more favorable climatic conditions for plant growth. The hybrids 16F26008, 16F26014, 16F26007, 201134020, 16F24007, 16F24008 were superior to the others and showed a better balance between nutritional value and nutrient production.