How low soil nutrient availability increases anthracnose severity and limits forage quality and yield in Bolivian Giant Sorghum

ABSTRACT Soil nutrient availability affects economically significant crops, yet its influence on forage sorghum remains poorly understood. This study aimed to assess the impact of soil fertility on Bolivian Giant Sorghum AGRI 002E (Sorghum bicolor) across morphological, sanitary, yield, chemical, and nutritional attributes. A completely randomized experimental design was employed, comprising two treatments and ten replicates, representing two soil fertility conditions: A (fertile) and B (low fertility). The experiment was conducted in the Brazilian savanna. Soils A and B differed mainly in potassium (K), phosphorus (P), base saturation, manganese (Mn), and zinc (Zn) (0.00-0.20 m), and potassium (K), phosphorus (P), sulfur (S), and Al 3+ saturation (0.00-0.40 m). Sorghum cultivated in soil A exhibited a remarkable 64.83 % increase in green forage mass compared to soil B, translating to a difference of 24.04 Mg ha -1 in dry matter. Furthermore, sorghum in soil A maintained a significantly higher number of live leaves, approximately 5.6 more than soil B, albeit experiencing a 33.59 % reduction in estimated leaf area under the lower soil fertility condition. Significantly, a conspicuous negative correlation emerged between the severity of anthracnose and morphological and yield traits. Under conditions of low soil fertility, the severity of anthracnose was six times higher, the dry forage yield was 13.04 Mg ha -1 , and this hindered structural development, increased fibrous structures, diminished crude protein, and reduced digestibility.