Alternative Agronomic Management Practices Through Fertilizer, Irrigation, and Plant Density Adjustments for Hybrid Fodder Sorghum (<em>Sorghum bicolor</em> L. Moench)

Abstract

Purpose: The basal fertilizer recommendation for growing hybrid fodder sorghum varieties in uplands involves relatively high quantities of Urea, TSP, and MOP, with rates of 100:90:65 kg/ha for SX-17 and 150:62:37 kg/ha for Dairy green. For both initial and ratoon crops, it is recommended to apply 150 kg/ha of urea as a top dressing. This study investigated the impact of reducing the fertilizer application rate to 75% and employing alternative agronomic practices on hybrid fodder sorghum varieties grown in lowland fallow paddy fields in the dry zone during the Yala and third seasons.Research Method: The agronomic management practices, including four basal fertilizer rates (Urea:TSP: MOP) of 100:90:65 (BD1), 150:62:37 (BD2), 75:68:49 (BD3), and 113:47:28 (BD4); two top-dressing urea fertilizer rates of 150 (TD1) and 112.5 kg/ha (TD2); two plant spacing configurations of 45x30 (WS) and 45x15 cm (NS); and two irrigation interval regimes, 5 days up to 30 days followed by 8 days (SI) and 7 days up to 30 days followed by 10 days (LI) were investigated. These factors were combined into four agronomic management packages: AMP1 (BD1, TD1, WS, SI), AMP2 (BD2, TD1, NS, SI), AMP3 (BD3, TD2, WS, LI), and AMP4 (BD4, TD2, NS, LI). The study used a split-plot design with three replicates and assessed various parameters, including plant height, stem diameter, plant weight, leaf area index (LAI), number of tillers, and fodder yield in both the initial fodder sorghum crop and the first ratoon crop. The crops were harvested when 50% of the panicles on the plants were at the milk and dough grain stages.Findings: The initial crop exhibited significantly heavier plants having wider stems when grown with higher fertilizer rates, wider plant spacing, and shorter irrigation intervals in AMP1. Irrespective of fertilizer rate and irrigation interval, the initial crops tended to have higher LAI with narrow plant spacing in AMP2 and AMP4. In the ratoon crops, wider plant spacing in AMP1 and AMP3 resulted in clumps with a greater number of tillers and heavier plants. However, the ratoon crops also exhibited higher LAI with narrow plant spacing in AMP2 and AMP4. Total fodder dry matter yield (DMY) in AMP2 and AMP4 with narrow plant spacing was significantly greater for both varieties. Furthermore, the DMY was not affected by fertilizer rate and irrigation interval.Value: Hybrid fodder sorghum varieties (SX-17 and Dairygreen) cultivated at higher plant density, along with reduced fertilizer (75%) and irrigation, can produce comparable fodder yield (21.1 and 26.1 MT/ha, respectively) to those grown at lower plant density with more fertilizer and irrigation (24.6 and 28.1 MT/ha, respectively) in lowland paddy fields during Yala and third seasons in the dry zone.