Annual Variation of Above Ground Biomass, Vegetation Height and Crude Protein Yield on the Natural Rangelands of Erzurum

Authors: Ali KOÇ, Ahmet GÖKKUŞ

Abstract: This study was conducted on the natural rangelands of GŸzelyurt Village in Erzurum (Eastern Turkey) in 1990-91 in order to investigate changes in the above ground biomass, vegetation height, crude protein yield and content, and the best times to start and finish grazing. The research was conducted on 20 plots of 500 m2. Samples used to measure biomass and crude protein content were taken at fortnightly intervals (weekly for plant height) from May to November . The results were as follows; 1. Above ground biomass at the beginning of May was 7.9 g/m2 and 9.7 g/m2 in 1990 and 1991 respectively and these increased rapidly to their maximum levels on July 10th in the first year (85.0 g/m2) and on July 4th in the second year (66.6 g/m2). Then above ground biomass decreased rapidly until October in 1990 when a slight increase occurred. In 1991 this decrease lasted until mid-September when a rapid increase was observed towards the end of September owing to seasonal precipitation in the late fall. 2. Vegetation heights were 25.7-44.0 mm respectively on the sampling dates of both years. Then the vegetation height increased to its maximum values on July 10th 1990 (251.7mm) and on July 18th 1991 (251.0 mm). 3. The crude protein content of hay was 18.5 % and 16.5 % on May 3rd in 1990 and 1991 respectively, decreasing steadily to 3.9 % on November 1st in 1990 and to 5.8 % on September 12th in 1991. The changes in protein yield were also in line with the crude protein content. 4. The period from the start of rapid vegetation growth (i.e. an increase in the height and biomass of vegetation) to the stage when the average daily temperature fell to 0 ¼C was regarded as the best grazing time, which coincided with the mid-May to late October period. When grazing maturity was reached poplars (Populus nigra var. pyramidalis) started to show new leaves and Taraxacum officinale bloomed. So these growing stages of the plants were accepted as the indicators for the start of grazing.