Treatment of endophyte-infected tall fescue [Lolium arundinaceum (Schreb.) Darbysh] with the broad leaf herbicide Chaparral® can mitigate fescue toxicosis and enhance forage quality by suppressing seedhead emergence. Applying the herbicide to fescue pastures also reduces forage mass and promotes severe spot grazing when pastures are continuously grazed. A grazing experiment was conducted with steers (2013) and heifers (2014) to evaluate animal and plant responses in fescue-bluegrass (Poa pratensis L.) mixtures treated with Chaparral to determine the effects of grazing management on pasture carrying capacity, nutritive values, botanical composition, and animal performance. Continuous and rotational (i.e., four subdivisions to provide a 7-d grazing period and a 21-d rest period) grazing treatments were assigned to six, 3.0-ha fescue-bluegrass pastures in a randomized complete block design with three replications. Each pasture had six tester animals, and stocking rates were varied using put-and-take animals. Pastures were grazed from 16 April to 8 July 2013 (Year 1) and 20 May to 12 Aug (Year 2) and cattle were blocked by body weight for allotment to pastures. Pasture carrying capacities were greater (P = 0.07) for rotational compared to continuous pastures across both years. Calves on rotationally grazed pastures had greater average daily gain (P = 0.03) and gain per acre (P = 0.05) than those on the continuous treatment across both years. Canopies of continuously grazed pastures contained less (P = 0.01) tall fescue than those in rotationally grazed pastures. Herbage in pre-grazed paddocks had less NDF and ADF than post-grazed paddocks and continuously grazed pastures in 2013 (P < 0.10), but did not differ in 2014 (P > 0.10). In vitro digestible dry matter was greater (P = 0.07) in pre-graze rotational pastures in 2013 compared with continuous and post-graze rotational, and IVDDM did not differ (P < 0.01) between pre-graze rotational and continuous in 2014, but was greater than post-graze rotational. Crude protein was lower (P = 0.06) in both years in post-graze rotational pasture than in continuous or pre-graze rotational pasture, which did not differ. In 2013, there was no difference (P = 0.60) in root WSC among treatments; however, in 2014, WSC levels were greater (P = 0.01) in rotationally grazed pastures compared with continuously grazed pastures. This grazing experiment indicated that rotational grazing of Chaparral treated fescue-bluegrass mixtures can improve both animal performance and the sustainability of pasture productivity.

This study focuses on modelling community productivity, species abundance and richness, and the impact of climate change and alternative phosphorous fertiliser application strategies on pasture productivity by integration of decision tree and regression modelling approaches with a geographical information system (GIS) in a naturalised hill-pasture ecosystem in the North Island, New Zealand, using data derived from research conducted on hill-pastures over the last several decades. The results indicated that the decision tree models had a high predictive capability and clearly revealed the relative importance of environmental and management factors in influencing community productivity, species abundance and richness. Spring rainfall was the most significant factor influencing annual pasture productivity in the North Island, while hill slope was the most significant factor influencing spring and winter pasture productivity. Annual P fertiliser input and autumn rainfall were the most significant factors influencing summer and autumn pasture productivity, respectively. For species functional group abundance, soil Olsen P was the most significant factor influencing the relative abundance of low fertility tolerance grasses (LFTG) and moss, while soil bulk density, slope and annual P fertiliser input were the most significant factors influencing the relative abundance of legume, high fertility response grasses (HFRG) and flatweeds, respectively. Legume abundance was the most significant factor influencing species richness in the hill-pasture. Species richness increased with an increase in legume abundance and showed a tendency for a hump-shaped response. Grazing animal species also had a significant effect on species richness; pasture grazed by sheep had more species than pasture grazed by cattle. Climate change scenarios of temperature increases of 1-2 °C and rainfall changes of -20% to +20% would have a great impact (-46.2% to +51.9%) on pasture production in the North Island. Pasture in areas with relatively low rainfall had a higher response to increased P fertiliser input than pastures in areas with a relatively high rainfall. In conclusion, the integration of a GIS with decision tree and regression models in this study provided an approach for effective predictive modelling of community productivity, species abundance and richness in the hill-pasture. This modelling approach can also be used as a tool in pasture management such as in assessing the impact of climate change and alternative fertiliser management on pasture production.