Assessment of Sulfur Deficiency in Soils through Plant Analysis in Three Representative Areas of the Central Highlands of Ethiopia-IV

Abstract

Field survey was conducted in Arsi(Ar), East Shewa(ES) and Oromia Liuu(OL) zones in 2012-15 cropping seasons, aimed at assessing sulfur(S) status of soils through plant analysis. The general information on land-use, soil types, were collected using semi-structured questionnaire to trace past fertilizer use. For the purpose of the reliability of data, out of 350 surveyed farmers’ fields or samples, randomly selected 200 wheat seed samples were considered. Based on the critical levels(CLs) estimated for TS content in wheat seed, 0.12%, about 61.8% of the fields in Arsi were found to be severely deficient in S, and 17.7% were marginal, necessitating the application of external S in about 79.5% of the studied fields. Likewise, in ES, about 51.5% fields were found severely deficient in S, and 30.3% were marginal, again necessitating the application of external S in about 81.8% of fields. In OL, about 63.6% of the fields were severely deficient in S, and 24.2% were marginal. From the study, therefore, across all 3 locations, 59.0% of studied fields were severely S deficient and 24% were marginal. This necessitates the application of external S (full dose or some supplemental amount, depending on soil-test results) in about, 83.0% of the fields in three studied areas. This extent of S deficiency is comparable when the CL for N/S-ratio in wheat seed is 15:1. But, when the CL is 17:1, inconsistencies observed. In summary, the study affirmed that, S deficiency is becoming wide-spread in annually-cropped agricultural lands in the country. Hence, there is a need to integrate S in balanced fertilizer formula, if soil-test and crop-response data are available. In doing so, S from known/trusted sources can be blended with DAP or TSP for applying it into soils, with recommended doses of other nutrients, especially nitrogen and phosphorus. Sulfur can come from locally available source, (gypsum), to use its integrative benefits and economize fertilizer use.