Abstract
AbstractPotassium (K) outputs comprise removals in harvested crops and losses via a number of pathways. No specific environmental issues arise from K losses to the wider environment, and so they have received little attention. Nevertheless, K is very soluble and so can be leached to depth or to surface waters. Also, because K is bound to clays and organic materials, and adsorbed K is mostly associated with fine soil particles, it can be eroded with particulate material in runoff water and by strong winds. It can also be lost when crop residues are burned in the open. Losses represent a potential economic cost to farmers and reduce soil nutritional status for plant growth. The pathways of loss and their relative importance can be related to: (a) the general characteristics of the agricultural ecosystem (tropical or temperate regions, cropping or grazing, tillage management, interactions with other nutrients such as nitrogen); (b) the specific characteristics of the agricultural ecosystem such as soil mineralogy, texture, initial soil K status, sources of K applied (organic, inorganic), and rates and timing of fertilizer applications. This chapter provides an overview of the main factors affecting K removals in crops and losses through runoff, leaching, erosion, and open burning.
Highlights
Potassium (K) outputs comprise removals in harvested crops and losses via a number of pathways
Potassium is removed in harvested crops, a necessary and important part of agriculture and food production, but it is lost by erosion, leaching, and open burning
Leaching is the displacement of K below the rhizosphere volume by water percolating down the soil profile
Summary
Harvested plant K is the quantity of K in plant material removed from a given area. The rate of K removal per unit area increases when the total K accumulation in harvested plant organs increases. Crop residues may not be returned to the same field from which they were harvested (e.g., pomace and bagasse) Understanding both the rate of uptake and the total amount of K accumulated in the crop during the growing season, and in the harvested portion removed during harvest, is required for assessing the seasonal crop demand. Rogers et al (2019) measured total K accumulation of five barley (Hordeum vulgare L.) cultivars and found it peaked at the soft dough stage (253 kg K haÀ1) and declined to 172 K kg haÀ1 at physiological maturity This loss of 81 kg K haÀ1 from the biomass occurred at the same time as a small increase in K in the barley heads (from 37 to 42 kg K kg haÀ1). Samples of harvested crops should be periodically analyzed in the laboratory in order to confirm the quantity of nutrients being removed from the field
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