Dietary Cation-Anion Difference of Timothy as Affected by Development Stage and Nitrogen and Phosphorus Fertilization

• Published in: Agronomy journal Vol. 98; no. 3; pp. 774 - 780
• Main Authors: Pelletier, S, Belanger, G, Tremblay, G.F, Bregard, A, Allard, G
• Format: Journal Article
• Language: English
• Published: Madison American Society of Agronomy 01.05.2006
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; dietary cation anion difference; equations; fertilizer rates; forage composition; forage crops; forage grasses; Fundamental and applied biological sciences. Psychology; harvest date; mineral content; nitrogen fertilizers; nutritive value; Phleum pratense; phosphorus fertilizers; plant development; plant nutrition; soil fertility; Quebec; Non metal; Monocotyledones; Phleum; Nitrogen; Phosphorus fertilization; Group VA element; Anions; Diet; Gramineae; Agronomy; Angiospermae; Herbaceous plant; Spermatophyta; Cations; Developmental stage; Influence factor
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2005.0229

Dry dairy cows (Bos taurus) fed forages with a high dietary cation-anion difference (DCAD) are more likely to develop hypocalcaemia. We determined how development stage at harvest and N and P fertilization can be used to reduce the DCAD to <250 mmolc kg-1 dry matter (DM) for timothy (Phleum pratense L.) grown on a soil high in K content. Stages of development (stem elongation, early heading, late heading, and early flowering) in spring growth, and treatments of P (0, 15, 30, and 45 kg ha-1) and N (0, 60, 120, and 180 kg ha-1) fertilization were evaluated. Concentrations of K, Na, Ca, Mg, Cl, S, and P of timothy were determined and the DCAD was calculated with a short (DCADS) and a long (DCADL) equation. From stem elongation to early flowering, DCADS decreased from 326 to 196 mmolc kg-1 DM and DCADL from 297 to 181 mmolc kg-1 DM; this reduction was attributed to a decrease in K concentration and a slight increase in Cl concentration with development stage. Nitrogen fertilization increased DCADS and DCADL only at stem elongation; the lack of a response at later stages of development is explained by the concomitant increase in both K and Cl concentrations with increasing N fertilization. Phosphorus fertilization did not affect DCADS and DCADL even though it increased timothy P concentration. Harvesting timothy at late heading, with an appropriate N fertilization to ensure adequate yield, is an option to produce a forage with a DCAD of <250 mmolc kg-1 DM on a soil high in K.