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University of KwaZulu-Natal (2004)

Nutrient cycling in grazing systems.

Kahsay, Anwar Brhanu.

Titre : Nutrient cycling in grazing systems.

Auteur : Kahsay, Anwar Brhanu.

Université de soutenance : University of KwaZulu-Natal

Grade : MASTER OF SCIENCE IN AGRICULTURE 2004

Résumé
This research was conducted at the University of KwaZulu-Natal, Pietermaritzburg, South Africa. The research encompasses five different studies to assess nutrient cycling in intensive and extensive grazing systems with a view to optimising livestock production. The first study was designed to assess the effect of teff-lucerne mixtures on teff, lucerne and teff-lucerne mixture yields. Lucerne and teff-lucerne mixtures benefited from the association. The overall soil N content of the teff-lucerne mixture plots was greater than the teff alone plots. The second study focused on teff-leucaena association evaluation. It had two leucaena plant row spacings as treatments, 180cm and 120cm, respectively. Teff grown in mixture with leucaena produced a total teff dry matter (DM) of 7931.57 kg ha¯¹ for the 180cm row spacing and 8329.57 for the 120cm row spacing compared to the 3548.93 kg ha¯¹ of DM obtained from the teff alone treatment. The teff-Ieucaena stand also had a greater DM yield response to leucaena row spacing compared to the teff alone. In terms of nutritive quality, all stands from the teff-leucaena plots were better than the quality obtained from the teff alone plots. Total N content of teff from the l80cm row spacing was 21.83 g kg¯¹ and that from the 120cm 16.07 g kg¯¹ compared to the total nitrogen (N) content of 19.77 g kg¯¹ of the teff alone treatment. The total phosphorus (P) content was 2.73, 1.96 and 2.07 g kg¯¹ for the 180cm, 120cm and teff alone treatments respectively. However, the total soil N content was higher for the teff alone plot than for the teff-leucaena plots, which are 1.91, 1.48 and 100 g kg¯¹ for the teff alone, 180cm and 120cm treatments respectively. The third study was designed to assess the effects of different N fertilizer application rates on teff yield response. The rates applied were 0, 50, 100 and 150 kg N ha¯¹. There was significant difference in teff response of the three N fertilizer application rates compared to the control and teff DM yield response was lower for the 150 kg N ha¯¹ (838 kg ha¯¹) treatment compared to the control (553 kg ha¯¹). Both teff DM and nutritive value were higher in the plots treated with N fertilizer than in the plot which received no N fertilizer (control). The soil N content was also higher in those plots treated with N fertilizer.

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