Phytoextraction of Soil Phosphorus by Potassium-Fertilized Grass-Clover Swards

Abstract

In the development of the Dutch National Ecological Network, many hectares of arable land are converted to nature areas to protect plant and animal species. This encompasses development of species-rich grasslands. On former agricultural land on sandy soils, this development is often hampered by relatively high phosphorus (P) levels, which also cause eutrophication. Standard practices to decrease the amount of P are either topsoil removal or long-term mowing of low-yielding established grassland. Both methods have disadvantages, and there is a need for additional techniques. As an alternative, phytoextraction ("mining") of soil P has been proposed. We tested a new technique of mining without mineral N fertilizer by cropping an intensively mown grass-clover with potassium (K) fertilization that could potentially be used as cattle feed. A long-term field experiment was conducted, comparing soil P removal by grass-clover swards with and without supplementary K fertilization on a sandy soil. During the experiment, which ran from 2002 to 2009, soil P levels and nutrient contents of grass-clover were measured, and P and K balances were calculated. Our results show that grass-clover with K fertilization removed excess soil P (also at lower P levels) at a relatively high rate (34 kg P ha −1 yr −1, significantly higher than without K fertilization; P < 0.05) and produced reasonable yields of grass-clover. Our P balance suggested reduced leaching from the topsoil during this experiment. For nature restoration in agricultural areas, this tool opens many possibilities. Phytoextraction of Soil Phosphorus by Potassium-FertilizedGrass-Clover Swards Bart G. H. Timmermans* and Nick van Eekeren O n a global scale, awareness is growing that the amount of phosphorus (P) available for fertilizer production and crop growth is limited and that a potential P crisis is looming (Abelson, 1999;Herring and Fantel, 1993). At the same time, some western European countries, including The Netherlands, are having problems with excessive P levels in agricultural soils. In The Netherlands, an extensive network of green corridors, called the National Ecological Network, is being implemented (Bakker et al., 2015). The idea originated in the 1990s and aims to protect species of animals and plants. The National Ecological Network encompasses various types of nature areas. In this context, many hectares of arable land have been transferred to nature reservations, and many more are planned (originally the plan was to implement 728,500 ha in 2018, but the ambition has decreased somewhat in terms of area and planning). In most of these former agricultural soils, long-term applications of fertilizers and animal manure in the past, which were stopped after land acquisition by nature organizations, have led to an imbalance in the levels of soil nutrients. Although these soils often have high levels of relatively immobile soil P, the more mobile nitrogen (N) and potassium (K) have often become suboptimal according to agricultural standards because of ...

Grass–Legume Forage Systems Effect on Phosphorus Removal from a Grassland Historically Irrigated with Reclaimed Wastewater

“…The ranges of P removal are also dependent on the type of forage species and agronomic management practices utilized. For example, Ketterings et al [69], Brink et al [70], Silveira et al [30], and Read et al [32] reported a range of 8-189 kg P ha −1 for different warm-season grasses and cool-season grasses and legumes, approximately 4-45 kg P ha −1 [33,36]. Phosphorus removal in our study falls well within the cool-, warm-season grasses, and legumes ranges reported.…”

“…arvense (L.) Poir. ), and hairy vetch (Vicia villosa Roth) on their P or other nutrient acquisition potential [27,[33][34][35][36]. The overarching conclusion is that the different forage species differed in their P acquisition and biomass production potential, thus differing rates of P removal.…”

Up on the roof and down in the dirt: Differences in substrate properties (SOM, potassium, phosphorus and pH) and their relationships to each other between sedum and wildflower green roofs

“…Phosphorus levels from sedum roof substrate samples in this study were found to be significantly higher than the wildflower ones, which may have implications for nutrient runoff which can affect adjacent watercourse quality [50]. Wildflower roofs may have lower phosphorus concentrations than sedum roofs as they are regularly mowed, and mowing regimes have been seen to decrease phosphorus levels in arable grasslands [51].…”

White clover (Trifolium repens) population dynamics are partly dependent on timing of seminal taproot death

“…Death of the seminal taproot causes the plant to rely solely on the nodal roots. The smaller and more shallow nodal roots are less able to exploit the soil for water and nutrients, therefore they make white clover more vulnerable to moisture and nutrient stress and invasion by pathogens (Bonesmo & Bakken, 2005; Brock, 1988; Jones, 1980; Nichols et al, 2015; Timmermans & van Eekeren, 2016). The transition phase from a taprooted plant to a plant relying on nodal roots is crucial in the development of white clover (Brock et al, 2000; Brock & Tilbrook, 2000).…”