The effects of nitrate nitrogen and phosphate on the nodulation and nitrogen fixation of white cliver (Trifolium repens L.): a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University

Abstract

It is a well established fact that the presence of nitrate ions can depress nodule development on legume roots, but recent studies in Queensland (Gates, 1970) have shown that this sensitivity can be ameliorated if phosphate levels are maintained at a high rate. Gates studies involved tropical legumes and their appropriate rhizebial symbionts, and this study was conducted to ascertain whether a similar situation obtains with a temperate species like Trifolium repens (White Clover). Quantitiative information on the effect of nitrate nitrogen and phosphate on nitrogen fixing activity in white clover was also lacking, and an attempt was made to rectify this deficiency by examining the changes in rate of ethylene production per plant or mg nodule (dry weight) with the application of nitrate nitrogen and higher rates of phosphate.