Long-term negative phosphorus budgets in organic crop rotations deplete plant-available phosphorus from soil

Abstract

In organic farming, phosphorus (P) can be imported in mineral form with rock phosphate, feedstuff for livestock or suitable organic fertilizers. Many organic farmers, however, rely on biological activation of soil P reserves and tolerate P deficits, not knowing when soil reserves will be depleted. We hypothesized that under conditions of a long-term negative P budget in organic farming, the decline in readily available soil P pools would be less pronounced in dairy systems (arable land and grassland) than in stockless systems (arable land), due to higher shares of forage legumes in crop rotations, longer plant soil coverage, and manure backflow. From 2001 to 2013, we analyzed those systems on one site in North Germany. We assessed topsoil for plant-available soil P concentration [P(CAL)], mineral soil P fractions (Hedley), organic P, acid and alkaline phosphatase, and microbial activity (dehydrogenase). We measured P(CAL) each year on all fields of the crop rotations and grassland. The other soil characteristics were determined only in selected fields in 2001, 2009, and 2013. We observed that in grassland, all mineral P fractions, organic P contents, and microbial activity were considerably higher than in arable fields. On average, soil P(CAL) content decreased significantly in all systems (stockless arable −1.71, dairy arable −1.41, grassland −3.18 mg P kg −1 year −1), but the soil threshold value deemed to be sufficient for P supply (>44 mg kg −1) was preserved. The readily available inorganic P fractions (H 2 O-P, NaHCO 3-P) were also lower in 2013 than in 2001. Our data does not support a different development in either arable system. We could show that higher shares of forage legumes and manure recycling in an organic mixed arable dairy crop rotation and grassland do not necessarily mitigate decreases of plant-available P contents in soil as compared to a stockless system.

Stable nutrient flows in sustainable and alternative cropping systems of globe artichoke

“…2006 2009 2013 2016 2006 2009 2013 2016 2006 2009 2013 2016 2006 2009 2013 2016 2006 2009 2013 2016 2006 2009 only a few weeks before planting of subsequent crops to better synchronize residue nutrient release and nutrient uptake for the subsequent crop, which was also suggested by Cavigelli and Thien (2003) and Simpson et al (2011). By contrast, in the improved conventional system, fertilizers applied to the field in excess of plant requirements resulted in substantial accumulation of soil P, although our results are consistent with P surpluses that also occurred with mineral fertilizers (Shen et al 2014) and in conventional production with other vegetables (Nesme et al 2011;Yan et al 2013). Based on the soil K system budgets, the improved conventional system had unnecessarily high levels of K fertilization, which was also observed by Korsaeth (2012) for arable conventional systems in a 10-year trial.…”

Soil carbon (C), nitrogen (N) and phosphorus (P) stoichiometry drives phosphorus lability in paddy soil under long-term fertilization: A fractionation and path analysis study

“…Nayak et al [65] also suggested that phosphatase activities increased by increasing soil organic matter. In another study Ohm et al [66] also found positive relationship between soil carbon and phosphatase activities. Therefore, studying phosphatase activities could be helpful to understand the lability of P under long-term fertilization regulated by soil C:N:P stoichiometry.…”

Absorption spectrometric macronutrients review of soil health during taro crop production

“…The deficiency of Ca and Mg occurs in soils that are intensively cultivated. In same way, P balances the cropping systems but when more P is removed with the products than recycled via external inputs (21), it threatens the long-term sustainability of farming systems (19,21). While soil organic matter (SOM) and soil macronutrients are crucial elements of soil-plant ecosystems (22), the soil pH diagnoses soil nutrient deficiency or toxicity problem (23,24).…”