Phosphorus Fertilization of Annual Ryegrass and Comparison of Soil Phosphorus Extractants

Abstract

It is unclear how much phosphorus (P) fertilizer is needed to maximize annual ryegrass (Lolium multiflorum Lam.cv. 'TAM90') forage yield and nutritive value in lower-rainfall climates. It is equally unclear which soil-P extractant is most effective when making P fertilization decisions. A 3-yr field study addressed these issues using small replicated plots during the winter months in north-central Texas. The addition of P increased yields every year of the trial, but optimum levels depended on rainfall distribution: 19 kg P ha −1 yr −1 was optimum two years, while 28 kg P ha −1 yr −1 increased yields 51% the year with good mid-season moisture. The addition of P fertilizer did not increase forage crude protein or affect fiber concentrations but did increase P yields. Percent relative yield of ryegrass was correlated with Mehlich III soil test P, soil pH, and P application rate. Conversely, the acidified NH 4 OAc-EDTA soil P extractant failed to relate to percent relative yield.

Dairy Manure Compost Improves Soil and Increases Tall Wheatgrass Yield

“…Cherney and Cherney (2005) reported that P concentrations of timothy, orchardgrass, reed canarygrass, smooth brome, and tall fescue averaged 2.35, 2.87, 3.20, 3.08, and 2.78 g K kg -1 , respectively and ranged from 2.41 to 3.32 g P kg -1 depending on the year. Butler et al (2006) reported that annual ryegrass, when grown in the same environment as this study and fertilized with 0 to 48 kg P ha -1 yr -1 , had P concentrations from 1.9 to 4.0 g P kg -1 . These values are slightly greater than the values measured in the present study with tall wheatgrass.…”

“…) averaged 9770, 7970, 9707, 7881, and 9968 kg DM ha -1 , respectively (Cherney and Cherney, 2005). Butler et al, (2006) reported DM yields of annual ryegrass (Lolium multiflorum Lam.) under the same environment as this study, which ranged from 4550 to 10510 kg DM ha -1 when fertilizer rates ranged from 0 to 40 kg P ha -1 .…”

“…Cherney and Cherney (2005) reported CP values for timothy, orchardgrass, reed canarygrass, smooth brome, and tall fescue that averaged 105, 122, 123, 132, and 110 g kg -1 , respectively. Butler et al (2006) reported CP values ranging from 202 to 248 g kg -1 for annual ryegrass. Crude protein was greatest at the two highest compost rates (89.6 and 179.2 mg ha -1 ) in 2002-03 but did not differ between compost rates in the 2003-04 growing season (Table 4).…”

“…Two soil P testing methods, historically used to measure soil-P for both agronomic and regulatory purposes, ammonium acetate-ethylenediaminetetraacetic acid (NH 4 OAc-EDTA) (Hons et al, 1990) and Mehlich III (Mehlich, 1984), can vary considerably in their estimation of plant-available soil-P (Butler et al, 2006). It is unclear which soil testing method should be utilized to predict available soil P. The objectives in this study were to 1) document the effect of composted dairy manure on selected Windthorst soil characteristics, 2) determine the appropriate soil test for measuring soil P in a Windthorst soil, and 3) evaluate tall wheatgrass yield response to six rates of composted dairy manure.…”

Phosphorus in pasture plants: potential implications for phosphorus loss in surface runoff

“…Typically, pasture mass and P concentration quickly increases with soil test P concentration to an asymptote, after which factors other than soil P availability limit yield (Edmeades et al 2006;Saunders et al 1987). Beyond the asymptote, luxury uptake of P by the plant may parallel soil test P concentration (Butler et al 2007), but it is unknown if this would translate into potential P losses in surface runoff. Water extraction of plant and soil materials have enabled the concentration of plant P in surface runoff to be estimated (e.g., McDowell and Condron 2004;Sharpley 1981).…”