Abstract
Quantity-intensity (Q/I) characteristics are among conventional approaches for studying potassium dynamics and its availability. This was assessed to determine availability in four districts: namely, Sodo Zuria, Damot Gale, Damot Sore, and Boloso Sore, at three different land use systems (enset-coffee, crop land, and grazing land). Fractionation and dynamics of K sources were studied in soil samples, which were collected from 0–20 cm depth of each land system. The study revealed that water extractable K (H2O-K) concentrations ranged from 0.13 to 0.34 cmolc kg−1 soils at enset-coffee and grazing land use systems, respectively, and had a mean value of 0.28 cmolc kg−1 soils ammonium acetate extractable (NH4OAC-K) and nitric acid extract (HNO3-K) had a mean value of 0.25 cmolc kg−1 soils. In this study, the means of nonexchangeable- and exchangeable-K concentrations were of 0.11 and 0.14 cmolc kg−1 soils for land use types. Significant correlations were found between soil properties and Q/I parameters and among equilibrium solution parameters and Q/I parameters. There was no significant variation among the mean quantity values of the soils. The soils had higher change in exchangeable-K and potential buffering capacity than the enset-coffee land use soils, and the cop land had the highest values for these parameters. However, the enset-coffee land use soils had higher K-intensity. Therefore, application of site specific soil fertility management practices and research can improve soil K status and Q/I parameters to sustain productivity soils.
Highlights
Potassium is an essential and major nutrient for agricultural crop production [1]
Potassium exists in four forms in the soil, such as solution, exchangeable, nonexchangeable, or fixed and mineral or structural K forms [2]. e distribution of soil K among water soluble, exchangeable, and nonexchangeable forms is related to many soil properties including surface area, mineralogy, surface charge density, and degree of interlayering of clay minerals [3, 4]. ere are dynamic, equilibrium reactions between different forms of K in different soils depending on the parent material, degree of weathering, fertilizer, losses due to crop removal, erosion, and leaching [5]
Available P content of the soils ranged from 6.4 to 18.96 mg kg−1 and was low in accordance with Landon rating [33] throughout the locations (Table 1) indicating its inadequacy for crop production could be attributed to fixation on both clay surfaces. e cation exchange capacity (CEC) of the soils ranged from 15 to 24 cmolc kg−1 soils and was medium value as per the rating of Hazelton and Murphy [30]. e soil was low in exchangeable base which is due to the higher rainfall and seasonal variation normally observed in the area leading to intense leaching of bases and accumulation of exchangeable acidity in these soils
Summary
Potassium is an essential and major nutrient for agricultural crop production [1]. Potassium exists in four forms in the soil, such as solution, exchangeable, nonexchangeable, or fixed and mineral or structural K forms [2]. e distribution of soil K among water soluble, exchangeable, and nonexchangeable forms is related to many soil properties including surface area, mineralogy, surface charge density, and degree of interlayering of clay minerals [3, 4]. ere are dynamic, equilibrium reactions between different forms of K in different soils depending on the parent material, degree of weathering, fertilizer, losses due to crop removal, erosion, and leaching [5]. Several studies revealed that any activity associated with change in land use and agricultural management practices can affect soil properties and K dynamics [9,10,11,12], but the exchangeable and extractable K status of Wolaita soil K forms are unsatisfactory measures of nutrient availability since their concentration in the soil at any time is small in relation to long-term losses by crop removal and leaching and they give little indication of reserves of nonexchangeable but potentially available K. As limited research results are available on the balance of K for crop land systems in Kassa et al [13], the ability to predict yield responses to K fertilizers from K soil tests is limited and requires study; the objectives of this study were to (1) determine physical and chemical properties of the soils and (2) assess different types of K forms and dynamic in the different land uses
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