The use of fertilizers on grassland with particular reference to organic manure

Drysdale, Alexander Douglas (1964) The use of fertilizers on grassland with particular reference to organic manure. PhD thesis, University of Glasgow.

Abstract

Constituents of the urine of livestock which could have an effect OB pasture include nitrogen, phosphorus, potassium, water, indole-acetic acid, hormones and other substances, yet despite its high potential value as a fertilizer, virtually all the urine produced by stock in winter runs to waste. This waste of urine constitutes an important loss of plant nutrients but in addition it causes a pollution problem in water courses. The logical solution is the use of the urine as a liquid manure on the land but much more detailed and conclusive knowledge is required of its effect on plant growth, and in this thesis three experiments are reported in which different agronomic aspects of the use of the liquid manure on grassland have been studied. In the first experiment a preliminary comparison was made of the value of applications of liquid manure, conventional dry fertilisers ("Nitro-Chalk", muriate of potash and superphosphate) and water. In the second experiment detailed information was collected on the interaction of five application rates of liquid manure supplying from 0 to 400 lb nitrogen/acre and three application rates of fertilizer nitrogen ("Nitro-Chalk") supplying from 0 to 200 lb nitrogen/acre, with and without phosphate and potash fertilizers, when applied to a perennial ryegrass and white clover sward. The third experiment compared dressings of liquid manure and of dry fertilizer applied at the same time, both treatments supplying 69 lb nitrogen and 114 lb potassium/acre and applied in different months during the winter on six types of sward. These experiments explained many of the contradictory results obtained from earlier trials in which the effect of urine on pasture was studied. In the first two experiments in which applications were made in summer, liquid manure and dry fertilizer treatments which supplied equal or almost equal amounts of nitrogen and potassium resulted in similar yields of herbage, but the percentages of clover were higher and the yield of clover approximately double with the liquid manure treatments. In the third experiment substantial increases in herbage yield were obtained from winter applications of liquid manure, and these increases were again similar to those from the dry fertilizer. The responses were different from the six types of sward and also varied from month to month but it was found that dressings of liquid manure applied in February generally had the maximum effect on each sward. The effect of liquid manure was attributed mainly to its content of nitrogen and potassium. Although the liquid manure had only a very low phosphorus content, supplementing it with dressings of phosphate fertilizer had no effect on yield in the first experiment and gave only small increases at the high levels of nitrogen application in the second experiment. She water content of the liquid manure had no effect in itself on the yield of herbage or of clover, but the pH and the ammonia nitrogen contents of the liquid manure were higher than those of the dry fertilizer and this was suggested tentatively as a possible reason for the different effects that liquid manure and fertilizers had on clover. Botanical data obtained from the second experiment showed that changes in the clover cover of the sward on plots receiving liquid manure were generally compensated for by changes in the perennial ryegrass cover, and the total area occupied by clover plus ryegrass was similar under all treatments. The weed cover was decreased considerably by liquid manure applications and there was a corresponding increase in the proportion of bare ground. Liquid manure had a high potassium to nitrogen ratio and its application resulted in a marked increase in the potassium content of the soil and of the herbage, and a concomitant decrease in the calcium, magnesium, sodium and phosphorus contents of the herbage. This effect tended to be greater than that caused by applications of equivalent or almost equivalent levels of dry fertilizer and might be of considerable practical importance since the ratio of (using milli- equivalents) was increased to a level which in experiments elsewhere has shown a statistically significant correlation with an increased incidence of hypomagnesaemic tetany in dairy cows.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: J AB Smith
• Keywords: Range management
• Date of Award: 1964
• Depositing User: Enlighten Team
• Unique ID: glathesis:1964-73930
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 14 Jun 2019 08:56
• URI: https://theses.gla.ac.uk/id/eprint/73930