Site-specific potassium application based on the fertilizer potassium availability index of soil

Abstract

Soil varies in its potassium (K + ) content and ability to supply K + to crops. Site-specific K + management aims to optimize crop production and minimize K + loss from the soil. The spatial variation of available K + prior to fertilizer application, the K + fixation capacity of soil and soil texture need to be taken into account for variable-rate K + application. This study was done to measure the spatial variation of the fertilizer K + availability index (A I ), which shows the potential for K + fixation, and to develop a strategy that takes the spatial distribution of this index into account for site-specific K + application. To determine the fixation capacity, the linear relation between the amount of K + added to soil and the amount of K + fixed was determined on 40 topsoil samples. Samples of soil were equilibrated in a moist condition for 3 weeks after the addition of 0, 25, 75, 225 and 675 mg K + kg -1 . The increase in exchangeable K + was described by a linear relationship. The fertilizer K + availability index (slope) varied from 0.20 to 0.49, indicating 51-80% of added K + was converted to the non-exchangeable form. Principal component analysis (PCA) showed that the first two components accounted for most of the variation, 48.7 and 26.3% of total variation, respectively. A non-hierarchical cluster analysis (k-means clustering) identified four groups and the amounts of fertilizer K + required were calculated for each group. The results suggested that such classes could form a basis for variable-rate application to maintain an adequate K + status for crop production and to reduce potential K + loss from soil by leaching.

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“…Plants can take up K only from the soil solution and its availability is dependent upon the K dynamics as well as on total K content. K is present in soil in four main forms (Jalali, 2007). These are: (i) water soluble K (solution K) which is dissolved in the soil solution; (ii) exchangeable K is the form that is electrostatically retained by negatively charged soil colloids (clays, organic matter, sesquioxides); (iii) Non-exch-K is temporarily trapped between the interlayers of clay minerals (illites,…”

Site Specific Nutrient Management of an Intensively Cultivated Farm Using Geostatistical Approach

“…Iho and Laukkanen [5] reported that excessive phosphorus fertilization leads to potential soil-P accumulations and risk of P loss in runoff, negatively impacting the quality of receiving water bodies and precision phosphorus management strategy. Jalali [6] recommended site-specific or variable-rate potassium application based on the fertilizer potassium availability index of soil after grouping the soils into different management zones by a non-hierarchical cluster analysis. The spatial distribution of soil chemical properties is altered by agriculture, particularly by the application of fertilizers, amendments and tillage activities in the upper 10 cm depth of soil, even within a given soil plot [7].…”

Behaviour of Potassium Desorption Indicator in Some Semictitic Rich Soils at Northern of Iraq

“…Similarly, the rate of K + adsorption on illite and vermiculite was reported to be much slower than montmorillonite and kaolinite (Jalali, 2007, Al-Azawi, 2010. Clay minerals like semictite and kaolinite easily release all of their K + adsorbed than illite and vermiculite (Ghosh and Sing, 2001), upon removal rate by plants and rapidity at which potassium can be desorbed from the adsorbed phase whereas initial adsorption equilibrium solution levels serves as an index of potassium release (Rao et al, 2004, Jalali, 2006 . This equilibrium of potassium concentration appears to provide a better index of soil fertility.…”