Effects of nitrogen, potassium and organic matter on growth, chemical components and seed yields of IS 23585 forage sorghum cultivar
Sorghum is considered to be of African origin and subsequently spread to most countries in tropical and subtropical regions. Sorghum has outstanding resistance against drought conditions. Grain and fodder from sorghum plants have been used for man's and animals' consumption respectively for many decades. Experiments were conducted on Yasothon soil series (Oxic Paleustults) in Northeast Thailand, this is considered a poor soil. Growth parameters of sorghum were affected most by nitrogen chemical fertiliser followed by potassium chemical fertiliser. An increase in nitrogen level increased growth parameters and seed yields/ha of the sorghum plants whilst an increase in potassium also increased growth parameters and seed yields but to a lesser extent. High application rates of both nitrogen and potassium were required to achieve high total dry weights and seed yields/ha. Fermented cattle manure significantly increased growth parameters of the sorghum plants and soil properties. were also improved by cattle manure. Total dry weights and seed yields/ha were affected most by seasons and treatments whilst seasons x treatments had highly significant effects on seed yields/ha but not total dry weights/ha. In terms of economic viewpoint, optimum application rates for nitrogen at a range of 300-450 kg N/ha and 100 kg K20/ha for potassium plus 40 tonnes/ha of fermented cattle manure were the recommended rates for optimum above ground total dry weight (15,940-26,282 kg/ha) and seed yield (5,047- 6,374 kg/ha) of IS 23585 forage sorghum cultivar on Yasothon soil series. An increase in nitrogen fertiliser application increased estimated crude protein (CP) of the sorghum plants whilst potassium did not. Both nitrogen and potassium had no Significant effects on acid detergent fibre (ADF), neutral detergent fibre (NDF), and dry matter degradability (DMO). However, seasons had significant effects on CP, NDF, ADF, DMD and brix values. Treatments also had significant effects on all components except DMD, and brix values. Seasons x treatments had significant effects on all components except CP and brix values.