Determination of Veld Grazing Capacity and Nutrient Potential Using GPS Mapping

Abstract

Ten farms from a Smallholder Dairy Sector (SDS) were surveyed based on their nautical location relative to the Marirangwe Milk Collection Centre. Grass samples were taken by randomly throwing a one by one metre quadrant every 40 paces along a transect line on each farm. All the grass that fell within the area of the quadrant was cut at 5cm (approximate grazing level), identified by species and as palatable or unpalatable, bagged and weighed separately. A Global Positioning System (GPS) was used to take coordinates of the points each quadrant was thrown in order to derive a species map based on presence or absence of the species. This was done using moderate resolution imaging spectroradiometer (MODIS) satellite images. After converting the data into binary format, mapping was done using Integrated Land and Water Information System (ILWIS) version 3.3 GIS environment (Enschede, 2005).

It was found that there was a significant relationship between the Normalized differential vegetative index (NDVI) and the presence or absence of four species (P< 0.005) and these were Sporobolus pyramidalis (17% probability of occurrence), Heterogon contortus (18%), Stylosanthes guianensis (5%) and Eragrostis spp (9%).

Calculations of the potential palatable yield showed that the prevailing stocking rate (12 ha per Livestock Unit) of the veld in Marirangwe was under stocked and had a potential of meeting the metabolisable energy needs of 7,285 LSU in January when the veld is in peak nutritional condition.

It was concluded that the natural veld in Marirangwe had the potential of supplying adequate nutrients to the number of milking cows throughout the year, but there was need to harvest and store the grass, manage rampant burning and supplement the cows with other homegrown fodder in order to have a more year-round milk supply pattern.