a b s t r a c tRemediating saline-sodic soils with organic amendments is increasingly seen as a cheaper and sustainable alternative to inorganic materials. The reclamation potential of biochar, biosolids and greenwaste composts applied to a saline-sodic soil was evaluated in a laboratory leaching experiment using moderate SAR reclaimed water. Treatments included biochar, biosolids co-compost, greenwaste compost (all applied at a 75 t ha −1 rate), gypsum (50% soil gypsum requirement), biochar + gypsum, biosolids + gypsum, greenwaste + gypsum and a non-amended control. All treatments were subjected to a one month incubation after which, soils were filled in columns and leached using reclaimed water until 7 PV of water had passed. Cumulative leachate losses of Na + , Ca 2+ , and Mg 2+ were evaluated in addition to soil properties after leaching. Results show that leaching with moderate SAR water was effective in reducing the soil salinity and sodicity of all soils, irrespective of amendment application. However, incorporating biochar and composts significantly enhanced this effect. Salt leaching was higher in soils treated with organic amendments. Cumulative leachate losses of cations were significantly higher from biochar and compost treated soils compared to gypsum and unamended controls. Improvements in soil aggregate stability and saturated hydraulic conductivity were prominent in compost treated soils. After leaching, soil analyses indicated that organic amendments lowered significantly more soil EC e , ESP and SAR than that of the control soils and saturated the exchange complex with Ca 2+ . Soil pH was significantly reduced and CEC was significantly increased in only compost treated soils. Although individual organic amendment applications proved to be significant enough to remediate a saline-sodic soil, combined applications of gypsum and organic amendments were more effective in improving soil properties directly related to sodium removal including sodium leaching, hydraulic conductivity, ESP, and SAR, and therefore could have a supplementary benefit of accelerating the reclamation process.

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Core Ideas A soil with an ideal basic cation saturation ratio (BCSR) is said to maximize crop yields. Previous studies concluded higher crop yields are possible over a wide range of ratios. Scientific community generally disregards BCSR theory. Soil balancing effects on weeds, soils, and crop quality are critical knowledge gaps. The common philosophies that contextualize soil test results and fertilizer recommendations are sufficiency level of available nutrients (SLAN), buildup and maintenance, and basic cation saturation ratio (BCSR). The BCSR approach postulates maintaining an ideal ratio of basic cation (Ca2+, Mg2+, and K+) saturations on the soil exchange sites to maximize crop yields. The practice of adding amendments to alter the ratios of basic cation saturations in soils is called “soil balancing.” Bear, Graham, and Albrecht promoted this concept, with each suggesting a desired saturation ratio of Ca:Mg:K for optimum crop yields. Several researchers have tried to validate this theory with both greenhouse and field experiments but could not conclude that an ideal cation saturation ratio existed and found that crop yields were similar across a wide range of ratios. While the scientific community disregards this theory, some farmers, crop consultants, and commercial soil‐testing laboratories still use BCSR to guide their fertilizer recommendations. It is believed that soil balancing effectively controls weeds, insects, and pests and improves overall soil health for better plant growth, ultimately producing better crop yields. Some even argue that soil balancing improves nutritional quality of the harvested crop. However, contemporary research to objectively demonstrate such perceived benefits of practicing soil balancing is missing. This review presents a holistic overview of soil balancing, presents a literature review on BCSR, and identifies knowledge gaps, which need to be addressed to better understand the merits and limitations of soil balancing.

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The common philosophies that contextualize soil test results and fertilizer recommendations are sufficiency level of available nutrients, buildup and maintenance, and basic cation saturation ratio (BCSR). The BCSR approach postulates maintaining an ideal ratio of basic cation saturations on the soil exchange sites to maximize crop yields. The practice of adding amendments to alter the ratios of basic cation saturations in soils is called “soil balancing.” While the scientific community disregards this theory, some farmers, crop consultants, and commercial soil‐testing laboratories still use BCSR to guide their fertilizer recommendations. Earn 1 CEU in Soil & Water Management by reading this article and taking the quiz at http://www.certifiedcropadviser.org/education/classroom/classes/537.