The influence of soil pH on sorghum grain yields

Abstract

Sorghum bicolor (L.) Moench is sensitive to acid soil stress environments. Acid soil stress tolerance is quite complex and involves additively inherited characteristics dealing with aluminum and manganese toxicities and calcium, magnesium, and phosphorus deficiencies. Genotype‐by‐environment interactions in unstressed environments are normally high for yield parameters and stress environments escalate the problem. Thirty parental lines and hybrids were compared in the field at mean H₂O/KCI pH values of 6.6/5.9, 5.7/5.0, 5.0/4.6, and 4.4/4.1 from 1982–1988 on a Suches clay loam (Fluventic Dystrochrept). All yield data were compared against IS7173C (SC283), an internationally tolerant check. Mean yields decreased 19% as pH dropped from 6.6/5.9 to 5.0/4.6. Yields were reduced 67% as pH dropped from 5.0/4.6 to 4.4/4.1 which reinforced previous research indicating that soil pH must be below pH 4.9 (H₂O) and have less than 5% organic matter for proper acid soil stress screening and evaluation of sorghum. Soil aluminum saturation values averaging 50% provide a maximum level of stress for sorghum. Hybrids and parental lines responded differently to stress, with the most stable producer across environments and highest‐yielding hybrid being ASC599×GP140. Percent relative yield of SC283 and tolerance indices (low yield + high yield) gave parallel results and were particularly indicative of previous genotypic field responses. Hybrid combinations involving specific parental lines governed relative tolerance of each genotype.