Potassium critical level in soil for Teff (Eragrostis tef (Zucc.) Trotter) grown in the central highland soils of Ethiopia

Abstract

Responses to potassium (K) fertilizer are reported in different parts of Ethiopia in recent years, contrary to the general perception that K fertilizer was not necessary on the soils. However, use of adequate K level for maximum economic yield is possible only when soil test data are calibrated against response curve for a given crop and soil type. This pot trial was conducted to calibrate K soil test with the response of teff (Eragrostis tef (Zucc.)) at application of increasing levels of K. Random soil samples (0-20 cm) were collected from 60 locations having Mehlich-3 (M-3) K soil test values ranging from 16 to 910 mg kg −1 across 20 teff growing districts in the highlands of Ethiopia. The relative biomass yield of teff was significantly correlated with Mehlich-3 extractable K, suggesting that the extraction method fairly estimated the available soil K. Soil test M-3 extractable K values were categorized, based on relative biomass yield, as "very low" (< 55 mg kg −1), "low" (55-210 mg kg −1), "medium" (210-280 mg kg −1), "high" (280-500 mg kg −1) and "very high" (> 500 mg kg −1). And K application rates of 139 and 54 kg ha −1 for the very low and low K categories respectively would suffice for optimum teff yield. The critical limit of K in soil (M-3) using the graphical method was 210 mg kg −1 for the 85% relative biomass yield level. An inverse relation of yield response to the soil K status was observed suggesting that application of K fertilizer increases yield of teff in low status soils. However, field verification is required to draw sound conclusions.

Response of crops to fertilizer application in volcanic soils

“…(2017) reported that the application of an excessive amount of K can cause yield decline due to the antagonistic effect of the same on Mg. In contrast to this study, Mulugeta et al. (2020) reported a significant increase in tef grain and straw yields due to the application of K fertilizer in 67% of the tested locations covered by Vertisols.…”

“…(2011) who reported that K levels between 250 and 800 mg kg −1 are categorized as high. Based on the results of a pot experiment, Mulugeta et al. (2019) also reported K critical level of 210 mg kg −1 following the Mehlich-3 method ( Mehlich, 1984 ) for tef to achieve 85% relative biomass yield level in Vertisols of Ethiopia.…”

“…Recent studies on Ethiopian soils ( EthioSIS, 2013 ; ATA, 2014 ; ATA, 2016 ) categorized Mehlich-3 K values of <90, 90–190, 190–600, 600–900 and >900 mg kg −1 as very low, low, optimum, high and very high, respectively. Similarly, Mulugeta et al. (2019) categorized Mehlich-3 K of <210, 210–280, 280–500 and 500 mg kg −1 as low, medium, high and very high, respectively.…”

Effect of potassium levels on teff (Eragrostis tef (Zucc.) Trotter) growth and yield in Central Highland Vertisols of Ethiopia

“…The values of soil pH (H2O) ranged from 5.4 to 7.4 showing that most of the soils were slightly acidic to neutral in reaction. Based on the K critical levels generated for teff (Mulugeta et al, 2019), which categorized the Mehlich-3 K of <210, 210-280, 280-500, and >500 mg kg -1 as low, medium, high and very high respectively; the K values of the study soils were in the range from low to very high. On the other hand, according to EthioSIS (2013, 2016) which categorized Mehlich-3 K values of < 90, 190-600, 600-900 and >900 mg kg -1 as very low, low, optimum, high and very high; the K status of the soils are in the range of low to medium.…”

Use of infrared spectroscopy and geospatial techniques for measurement and spatial prediction of soil properties

“…Because of limited knowledge on the K dynamics in Ethiopian soils and the absence of a remarkable response to K application, there has been sweeping generalization on K status in Ethiopian soils and as a result, there has not been adequate focus given to potassium in the national fertilizer scheme (Mesfin, 2007). Recently, however, a highly negative K balance and deficiency as well as responses to application of K fertilizer is reported in different parts of Ethiopia, contrary to the general perception that K fertilizer was unnecessary for the soils (EthioSIS, 2016;Mulugeta et al, 2019). So, site-specific applications of K-fertilizers would help to gain more responses from crops.…”