Effect of Levels and Types of Nitrogen Fertilizer on The Palatability of Orchardgrass in Shading Culture

Abstract

This paper described the palatability of orchardgrass which was cultivated with the different levels and types of nitrogen fertilizer under the condition shading 50% of solar radiation with cheese-cloth. Fertilization was designed as follows, at the experiment of the different nitrogen levels, 0.2 and 1, 2kg of nitrogen/are were applied with urea at each of four dressings in a year, and at the experiment of the different types of nitrogen fertilizer, 0.4kg of nitrogen/are was likewise given with urea, ammonium sulfate or ammonium nitrate. Palatability was evaluated with a two-choice preference method in cut-feeding tests using sheep, and chemical composition of these forages was compared with each other. The palatability of orchardgrass varied considerably by means of application rates or types of nitrogen fertilizer. The orchardgrass applied low level of nitrogen (0.2kg/are) showed higher palatability than the one with high level of nitrogen (1.2kg/are). And the orchardgrass applied ammonium sulfate showed higher palatability than the ones applied urea or ammonium nitrate. In general, the forage plants of high palatability tended to accumulated relatively large amounts of 85% ethanol soluble- and total soluble-carbohydrate, and to contain far less total nitrogen and nitrate nitrogen than the forage plants of low palatability. It appears that the nitrate nitrogen is particularly an important substance affecting the palatability of shaded forage plants, because the difference above 0.23 unit of nitrate nitrogen concentration in the tested forage plants caused sheep to discriminate palatable and unpalatable ones, whereas no any distinction on palatability occured in the cases of below 0.11 unit of them.