Seasonal variations in chemical composition of pasture

Abstract

As part of a study of seasonal variations in chemical composition of pasture herbage Ca, Mg, K, and Na concentrations, and the ratios KI (Ca + Mg) and CaIP, were determined by monthly samplings at seven sites in the lower North Island. Grass and clover components were harvested separately at six sites, and grasses, clovers, and "other species" (herbs) at the seventh. Sub.plots were harvested by hand shears, after which sheep were allowed to graze before the plots were enclosed until the next sampling date. The seasonal patterns in herbage chemical composition were similar at all sites despite wide differences in soil, climate, and dry matter production. For Ca, the highest values occurred in summer and the lowest in mid winter. Calcium concentrations were higher, and the variations greater, in clovers than in grasses, and concentrations were even higher in "other species". Trends in Mg were seasonally ,imilar to those for Ca but were much less pronounced; and differences between grasses and clovers were generally small. Potassium showed marked monthly fluctuations which were generally similar in the grass and clover components suggesting an effect of stock urine. High levels occcurred in late winter, with a peak in early spring, and the lowest levels in early hummer. There were no clear trends in Na concentrations, which were generally quite high in both grasses and clovers. Very high levels in "other species" occurred in late autumn to early spring. The KI (Ca + Mg) ratio (in chemical equivalents) in the grass component generally remained above the proposed critical level of 2.2 for 3-4 months at most sites during the winter and early spring, indicating a possible grass tetany hazard. On the other hand, the CalP ratio (in percentages) tended to fluctuate about the suggested "ideal" value of 1.5. The results were generally in accord with data from previous investigations on New Zealand pastures.

Soil and pasture nutrient status on yellow-brown earth soils of the West Coast, South Island

“…There was little difference in P concentration in grasses and clovers, and the Mg concentration in clover was higher than in grasses. These results were similar to those of Metson & Saunders (1978).…”

The calcium requirements of pastures in New Zealand: A review

“…Pasture Ca concentrations in both clovers and grasses exhibit strong seasonal trends as demonstrated in seven sites on the East Coast (Metson & Saunders 1978) and one site in Taranaki (Edmeades et al 1983b). Pasture Ca concentrations are lowest in the winter and spring and highest in the summer.…”

“…Using these criteria, Smith & Cornforth (range 0.10-3.26) and that 86% of the sites fell within the optimal range as defined above, 13% were in the "safe excess" range and only 1% were less than 0.30%. Cornforth (1984) subsequently adapted the criteria established by McNaught (1969McNaught ( , 1970 by adding an additional category and allowing for the fact that legumes have a higher requirement for Ca than grasses (Metson & Saunders 1978) (Table 2). Other workers have modified this data further by averaging the above data to provide criteria for mixed pasture samples.…”

The Effect of Seasonal Variations, Covariations with Minerals and Forage Value on Itchgrass’ Foliar Silicification from Sudanian Benin

“…However, among the species they examined only Eustachys paspaloides and Andropogon schirensis showed enhanced silica accumulation with the growth period. Most other authors found lower concentrations of silica in plant leaves grown in the season [45][46][47]49]. We found concentrations depending on the phenological stage.…”