Assessing Potassium Mass Balances in Different Countries and Scales

Abstract

Estimating nutrient mass balances using information on nutrient additions and removals generates useful, practical information on the nutrient status of a soil or area. A negative input–output balance of nutrients in the soil results when the crop nutrient removal and nutrient losses to other sinks become higher than the nutrient inputs into the system. Potassium (K) input–output balance varies among regions that have different climates, soil types, cropping systems, and cropping intensity. This chapter illustrates the farm-gate K balances in major production areas of the world and their impacts on native K fertility and crop yields. On-farm and on-station research examples show significant negative K balances in South Asia and Sub-Saharan Africa, while China, the USA, Brazil, and countries of the Latin America Southern Cone highlighted continued requirement of location-specific K application to maintain crop yields and soil K fertility status at optimum levels.

Inorganic fertilizer use and its association with rice yield gaps in sub-Saharan Africa

“…This was not surprising as P availability is one of the major barriers due to its low historical use in agriculture ( Magnone et al, 2022 ). Likewise, this finding confirms a previous study ( Majumdar et al, 2021 ) showing significant negative K balances in SSA. Potassium depletion in soil has been exacerbated by the removal of rice straw for feeding cattle or burning, post-harvesting practices commonly observed in smallholder farmers’ fields in many SSA countries ( Johnson et al, 2023 ; Niang et al, 2017 ).…”

Estimating nutrient concentrations and uptake in rice grain in sub-Saharan Africa using linear mixed-effects regression

“…Concentrations of K, Mg, and B were all below optimal values for all 20 countries and should be a priority target nutrient for future interventions, including the relationship with grain yields. Probable causes of low K in rice grain in SSA countries are negative K balance described in Majumdar et al (2021) . It is rather surprising to see sub-optimal Mg concentrations even in irrigated lowland which should not suffer from Mg deficiency because adequate amounts are usually supplied in irrigation water ( Dobermann and Fairhurst, 2000 ).…”

The input reduction principle of agroecology is wrong when it comes to mineral fertilizer use in sub-Saharan Africa

“…Soils of SSA have typically low plant-available P due to low P concentration in the parent material and extended weathering, and because of low soil pH and binding of phosphates by Fe 3+ and Al 3+ cations (Margenot et al, 2016). Similarly, plant-available K in soils of SSA is generally low because of prolonged weathering over time and insufficient external inputs (Majumdar et al, 2021).…”