Prediction of Pasture Growth Rates from Climatic Variables

Abstract

Feed planning enables ranchers to use feed resources efficiently and increase profits. Feed budgeting requires estimates of expected daily growth rate (DGR) of pasture. The purpose of this study was to estimate DGR and determine if weather variables and herbage mass could be used to predict DGR for an irrigated pasture dominated by tall fescue (Festucu arundinucea Schreb.) and strawberry clover (Trifolium fragiferum L.). A single‐probe capacitance meter was used to estimate herbage mass over 2 yr. Daily growth rate was calculated during the rest periods on 16 rotationally‐grazed paddocks. Maximum and minimum daily air and soil temperature, and solar irradiance were recorded by a California Irrigation Management Information System (CIMIS) weather station located within the pasture. Average daily weather values and the herbage mass at the beginning of the rest period were independent variables in regression with DGR. Solar irradiance was the variable most closely correlated with growth rate, and when combined with beginning herbage mass in multiple regression, predicted DGR with R2 = 0.71 (Sy.x = 9.7) in year 1 and R2 = 0.68 (Sy.x = 5.5) in year 2. Maximum air temperature with beginning herbage mass predicted DGR with R2 = 0.67 (Sy.x × = 10.4) for year 1 and R2 = 0.67 (Sy.x =5.6) for year 2. All weather variables were highly correlated with each other and had similar effects on growth rate. Daily growth rate increased with increasing beginning herbage mass up to 2500 lb dry matter (DM)/acre. While the climatic variables in this study were not strong predictors of DGR, they may be useful for adjusting long term DGR averages to actual weather conditions. Research Question Pasture feed budgeting, as practiced in New Zealand, requires an estimate of expected daily growth rate (DGR) of pasture for each month. This study estimated monthly DGR and the influence of solar irradiance, air temperature, soil temperature, and the amount of herbage per unit area of pasture (herbage mass) on DGR for an irrigated pasture in California's Sacramento Valley. Literature Summary Regional estimates of DGR are readily available to pasture managers in New Zealand but not in California. Daily growth rates will vary as solar irradiance and air temperature change. Herbage mass also influences DGR. Daily growth rates are often greatest within a herbage mass range of 1000 to 2500 lb DM/acre. Below that range leaf area is inadequate to capture solar irradiance efficiently and above that range shading and aging leaf tissue reduces photosynthetic capacity. Study Description Herbage mass was estimated during the rest periods on a rotationally grazed, irrigated pasture. Herbage mass was estimated weekly from May to September, biweekly from mid‐February to April and October to mid‐November, and monthly from mid‐November to mid‐February. Daily growth rate was determined from the change in herbage mass divided by the number of days. Solar irradiance, air temperature, and soil temperature were obtained from a weather station located on the irrigated pa...

Forage availability from a temperate pasture managed with intensive rotational grazing

“…After August, pasture growth rates declined linearly from approximately 53 kg DM ha"' d"' in late August to .lbout 32 kg ba"' d*' by early October in all 3 years (Figure 1), a decline in pasture growth rate during autumn that is generally observed (Denison and Perry, 1990;Lile and George, 1993), and IS associated with changing canopy architecture in an environment of declining solar radiation and falling temperatures (Parsons and Robson, 1982). Due to these lower rates of pasture growth in autumn, herbage availability per cycle during September was reduced to about 1060 kg DM ha"' in al!…”

“…Denison and Perry (1990) related slower rates of pasture growth during stimmer to moisture stress. Lile and George (1993) observed fairly uniform growth rates (42-50 kg DM ha'' d"') from May to August under irrigation. Variation in growth rates during spring and summer was significantly reduced by suppressing reproductive tiller development in spring, which resulted in a more even distnbution of forage production through the grazing season (Korte et ai.…”

Sources of Variability of Evapotranspiration in California

“…However, now that more than 20 years of CIMIS data have been collected, the network's high spatial density makes it useful for climate analyses. To date, CIMIS data have been used in published studies with the objective of calibrating models to predict pasture growth rates (Lile and George 1993) and for evaluating the suitability of empirical ETo equations based on air temperature (Hope and Evans 1992;Hargreaves and Allen 2003;Alexandris and Kerkides 2003). The regional ETo signals contained in these data and the climate patterns that determine that signal have not been investigated previously.…”

Light Interception and the Growth of Pastures under Ideal and Stressful Growing Conditions on the Allegheny Plateau

“…The pasture growth available for grazing is a function of the available PAR, LI, NCE, abiotic stress and change in stored energy reserves [6][7][8].…”

“…Growth efficiency {ƒ(plant nutrition, temperature and moisture stress)} PhotoEff Photosynthetic efficiency {ƒ(plant nutrition, temperature and moisture stress)} PARInt PAR interception {ƒ(LAI or sward RHt, solar elevation, and daylength)} NightRes Night respiration {ƒ(night temperature)} GRoot Growth of roots {ƒ(net photosynthesis, temperature and moisture stress)} ΔSER Change in stored energy reserves Growth efficiency is dependent on plant nutrition [5], especially N, P and K, as well as temperature and moisture stress [6][7][8]. Photosynthetic efficiency is dependent on plant nutrition, leaf age [9][10][11], temperature and moisture stress.…”