Long-term rundown of plant-available potassium in Western Australia requires a re-evaluation of potassium management for grain production: a review

Abstract

Negative potassium (K) balances on farmlands globally are widespread because fertiliser K input is often less than losses (leaching) and removal of K in hay, straw and grain, which leads to a rundown of plant-available K. When soil K reserves are not large and the plant-available K pools are not well buffered, the risk of K rundown in soils is high. In the south-west of Western Australia, soil K rundown, particularly by continuous cropping or in systems where a large portion of crop biomass is removed, is increasing the prevalence of crop K deficiency even on soils where K was not previously a limiting factor for crop yields. While fertiliser K is required for adequate supply of plant-available K, maximising K use efficiency is also important for cropping profitability and sustainability in dryland agriculture. Plant K uptake and use efficiency can be affected by soil types, crop species and sequences, seasonal conditions, and K management. In water-limited environments, crop K nutrition, especially root access to subsoil K, plays a crucial role in promoting root growth, regulating plant water relations and alleviating biotic and abiotic stresses. Optimised use of both soil and fertiliser K is increasingly necessary to sustain crop yields under stressed conditions in the context of K rundown in soils.

Reducing Arsenic, Cadmium, and Lead Exposure in Urban Areas via Limiting Nutrient Discharges into Rivers

“…That suggests a minimal influence of human activities on TK levels. This might mainly be due to a common characteristic of agriculture worldwide - the insufficient application of potassium fertilizers - causing large-scale potassium deficiencies in farmland. , In the years ahead, with the promotion of agricultural technologies and policies, farmers may apply more potassium fertilizers in cropland, leading to a higher runoff of the potassium-containing nutrients to river sediments.…”

Comparison of soil analytical methods for estimating plant-available potassium in highly weathered soils

“…However, under exhaustive cut-and-removal pot trials, the slope of the regression line between soil readily available K (watersoluble K + exchangeable K) and cumulative K uptake by ryegrass increased progressively from less than 0.5 (Pal et al 2001a) or 0.59 (Darunsontaya et al 2012) after the first harvest to about 1 after the sixth harvest, indicating that soil water-soluble K and exchangeable K were almost the only forms of K taken by grass in the highly weathered soils from both WA and Thailand (Pal et al 2001a;Darunsontaya et al 2012). The reliance of plant K uptake on exchangeable K when there is a low contribution of nonexchangeable K suggests that soils formed from weathered parent materials will be vulnerable to K rundown due to negative K balances (Ma et al 2022). Further experiments should compare the performance of NH 4 OAc and TBK on the prediction of plant-available K and assess the contribution of non-exchangeable K to plant K uptake after multiple crop seasons, or exhaustive pot experiments, using soils with variable K reserves and mineralogy.…”

“…In both cases, negative K balances at the farm gate continue to exacerbate K deficiencies. In the region used for grain production in Western Australia (WA), due to continued removal of K in harvested grain and historically low fertiliser K application rates (Harries et al 2021), negative K balances threaten crop productivity due to declining soil K levels including on loam-and clay-textured soils that have not yet been assessed for K supply to crops (Ma et al 2022).…”

“…However, past research on K-crop response experiments has heavily focused on lighter textured soils in WA, like Tenosols, Chromosols and Kandosols, which occupy about 50% of agricultural soils in WA (Brennan and Bell 2013;van Gool et al 2018). Monitoring of soil K reserves is increasingly important in all soil types to ensure that soil K supply is not constraining grain yield (Ma et al 2022). Therefore, further study is needed to determine if there is a better soil test to measure plant-available K over a wider range of soil types that occur in WA, especially on the loam-and clay-textured soils which may contain K-bearing clay minerals and feldspar (McArthur 2004).…”

Ammonia volatilisation losses from urea applied to acidic cropping soils is regulated by pH buffering capacity

“…Southwestern Australia is a significant grain production region with approximately 8.5 million hectares cropped annually (Harries et al 2021), with Tenosols, Chromosols and Sodosols the dominant soil types throughout the cropping region (Ma et al 2022). Acidic topsoils [pH(CaCl 2 ) < 5.5] characterise more than 70% of the region's arable land (Gazey et al 2013), with urea application widely relied on as an inorganic N fertiliser to support crop production.…”