Relative ability of a range of crop species to use phosphate rock and monocalcium phosphate as P sources when grown in soil

Abstract

Abstract:Glasshouse experiments were conducted to compare the ability of a range of crop species to use the medium reactive Jordan phosphate rock (JPR), the highly reactive North Carolina phosphate rock (NCPR) and the highly soluble monocalcium phosphate (MCP) as P sources in a P-deficient silt loam when supplied with nitrate-N. Growth of wheat and barley resulted in excess anion uptake, a consequent rise in rhizosphere pH and yield increased in the following order: control c JPR c NCPR c MCP. Growth of buckwheat resulted in excess cation uptake, and as a result it used NCPR as effectively as MCP; the yield order was as follows: control c JPR < NCPR = MCP. Lupin, when supplied with nitrate, raised its rhizosphere pH and yield followed the same order as that for wheat and barley: control < JPR < NCPR c MCP. In contrast, when not supplied with nitrate and relying substantially on biological N, fixation, lupin absorbed a cation excess, lowered rhizosphere pH and the yield order was control < JPR = NCPR = MCP. Although rape and kale absorbed an anion excess and raised rhizosphere pH they were surprisingly effective at using phosphate rock as a P source; the yield order was control < JPR = MCP < NCPR. This was attributed to the known ability of rape to acidify its rhizosphere in a localised area just behind the root tip in response to P deficiency. The opportunity appears to exist for the strategic use of phosphate rock at times within arable rotations when species are present that can effectively use such P sources.

Green manure and phosphate rock effects on phosphorus availability in a northern Great Plains dryland organic cropping system

“…Previous work found another mustard species (Brassica juncea L.) to be highly responsive (P<0.01) to PR in a low P (4.5 mg kg −1 Olsen P) calcareous soil (Gupta et al 1988). It was somewhat surprising that buckwheat did not appear to contribute to the P uptake response to increasing PR rate, given buckwheat's documented ability to access P from PR (Haynes 1992;Zhu et al 2002). This ability should also make buckwheat capable of extracting P from Ca-P minerals that exist in soils with neutral to high pH, minimizing the effect of PR additions on buckwheat P uptake.…”

“…The absence of a biomass response to PR was attributed to lack of P limitation or low PR solubility in this high pH soil. Much of the previous work demonstrating that PR is highly available to buckwheat, mustards, and legumes has been conducted in controlled glasshouse experiments at lower pH and with adequate N and water availability (Haynes 1992;Rajan et al 1996;Zhu et al 2002), increasing the likelihood of a PR response. The positive effect of PR rate on P uptake was largely attributed to the notable P uptake response of mustard.…”

“…Plant-mediated biochemical mechanisms that facilitate PR dissolution include rhizosphere acidification and organic acid exudation (Hinsinger 2001;Horst et al 2001). For example, buckwheat (Fagopyrum esculentum L.) successfully dissolves PR by favoring cation uptake over anion uptake, producing a net efflux of protons (H + ) into the rhizosphere (Bekele et al 1983;Haynes 1992;Ray and Van Diest 1979;Zhu et al 2002). Legumes also enhance PR dissolution by this mechanism, particularly when they obtain most of their nitrogen (N) from N 2 fixation (Aguilar and Van Diest 1981;Haynes 1992).…”

“…Selected mustard species (Brassicaceae spp.) enhance P availability without rhizosphere acidification through high rates of organic acid exudation and P uptake that favor Ca-P mineral dissolution and phosphate desorption (Bekele et al 1983;Haynes 1992;Hoffland 1992;Hoffland et al 1989;Johnson and Loeppert 2006).…”

“…Certain crop species are able to enhance PR dissolution and utilization (Haynes 1992;Hoffland et al 1989;Rajan et al 1996). Plant-mediated biochemical mechanisms that facilitate PR dissolution include rhizosphere acidification and organic acid exudation (Hinsinger 2001;Horst et al 2001).…”