Mining of soil legacy phosphorus without jeopardizing crop yield

Abstract

Off‐site transport of excess soil P from repeated P fertilizer applications constitutes waste of a vital resource and poses an environmental risk. Excess P can be mined by growing crops without P addition until it is exhausted to the point of P deficiency. This study evaluated the utility of the “soil phosphorus storage capacity” (SPSC) as an indicator of safe P mining for acid soils. The SPSC predicts crop‐available legacy P in absolute terms, (i.e., kg ha−1; can be calculated from mg kg−1 if the bulk density and soil depth are known), which is not provided by current soil tests. Results show that mining provides sufficient P for crops when there is adequately negative SPSC. This study provides a “proof‐of‐concept” for SPSC, serving as an indicator of legacy P mining prior to the need for P fertilizer application. However, further study is needed to determine the negative P thresholds more precisely at which P mining would no longer provide adequate P for optimum crop yields.

Profitability of dual‐purpose rye cover crop as influenced by harvesting date

“…In these regions, excessive nutrients are typically applied each year leading to excess nutrient build up in the soil, for example, excessive P build up(Griffin et al, 2003;Jokela et al, 2011;Pagliari & Laboski, 2013;Sadeghpour et al, 2017;Toth et al, 2006). Thus, removing excessive nutrients, especially N and P, from the soil is desirable to minimize the likelihood of environmental pollution(Fiorellino et al, 2017;Nair et al, 2020). Therefore, in these regions, the value of nutrients removed by WCR should not be considered as a cost.…”

Watershed Response to Legacy Phosphorus and Best Management Practices in an Impacted Agricultural Watershed in Florida, U.S.A.

“…This suggests that the BMPs tailored to reduce legacy P and improve manure management/applications would be beneficial for those sub-watersheds as well. Nair et al [102] recommended the adoption of a "soil phosphorus storage capacity" to determine the site-specific phosphorus fertilization rates to first exhaust legacy P via crop uptake without impacting productivity. This study in Florida showed promising results as a viable way of mining legacy P through reduced fertilizer applications but could benefit from further research and development.…”

Can soil phosphorus sorption saturation estimate future potential legacy phosphorus sources?

“…As the function α varies, the initial work of Breeuwsma and Schoumans (1987) to determine PSS has been modified for wider use. First, the acid ammonium oxalate extractant was replaced by Mehlich‐3 extractant, due to the instability of the oxalate solution under normal laboratory conditions (i.e., the oxalate solution has to be kept in the dark), which required the extractant to be made fresh on a daily basis (Kleinman & Sharpley, 2002; Nair et al., 2020; Schoumans, 2009). Soil PSS (percentage basis) was calculated from Mehlich‐3 P (M3P), Al (M3Al), and Fe (M3Fe; mmol kg −1 ) according to Equation : …”

“…While several studies have measured PSS for a range of soils in the United States and Europe (Leinweber, Lunsmann, & Eckhardt, 1997; Lookman, Jansen, Merckx, & Vlassak, 1996; Nair et al., 2020; Schoumans & Chardon, 2015), less is known about the effect of land management on PSS under field conditions. This paper describes the effect of P application via mineral fertilizer, swine slurry, and grazing cattle on the PSS of three pastures, which were grid‐soil sampled in 2014, 2016, and 2018.…”

“…The degree (percentage) of soil phosphorus sorption saturation (PSS) is based on the premise that the saturation of Psorbing sites for a soil determines P release (intensity factor), as well as the level of soil P (capacity factor) (Breeuwsma & Silva, 1992;Dari et al, 2018;Kleinman & Sharpley, 2002). As PSS increases, there are fewer sorption sites remaining to bind additional P, enhancing the potential for P release to surface runoff or leaching water, and has been used as an environmental indicator for soil P (Nair et al, 2020;Sharpley, 2020;Sharpley, Daniel, Sims, & Pote, 1996;Sims, Maguire, Leytem, Gartley, & Pautler, 2002;Vadas, Kleinman, Sharpley, & Turner, 2005). The degree of soil PSS also provides an indication of the remaining potential of soil to adsorb and retain P that may be added from inorganic fertilizer or manure amendment or from grazing animals.…”