Abstract
Light serves as the main driving force of photosynthesis and therefore has a direct impact on growth and hence dry matter production. Since tropical forages have higher light saturation levels for photosynthesis compared to temperate forages, they are potentially more productive. However, even in the tropics where there is generally high insolation, occassional cloudiness, as occurs in the rainy season may reduce the level of irradiance ; also in some areas there may be the establishment of forages under plantation crops to maximize land use. The persistently high insolation in the tropics has been suggested as a significant contributor to the lower dry matter digestibility of tropical forages. Since dry matter digestibility generally decreases with increase in dry matter yield, it is not clear to what extent these decreases are due to light intensity. Very few experiments have examined the direct effects of insolation on the nutritive value of forages, and the few available have been mainly with temperate forages. Decreasing light intensity is reported to increase the crude protein content as well as the crude fibre content but results in a decrease in non-structural carbohydrate content. On the contrary, decreasing light intensity tends to decrease dry matter digestibility. Thus, this experiment was carried out to study the effect of light intensity on the growth, chemical constituents and digestibility of green panic (Panicum maximum var. trichoglume cv. Petrie).
