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Accueil du site → Doctorat → États-Unis → 1994 → Quantitative nitrogen and growth models of grain sorghum (cv. SRN-39) as influenced by mineral and/or bio-nitrogen from preceding forage legumes in Sudan

University of Nebraska - Lincoln (1994)

Quantitative nitrogen and growth models of grain sorghum (cv. SRN-39) as influenced by mineral and/or bio-nitrogen from preceding forage legumes in Sudan

Mirghani Saeed Mohamed

Titre : Quantitative nitrogen and growth models of grain sorghum (cv. SRN-39) as influenced by mineral and/or bio-nitrogen from preceding forage legumes in Sudan

Auteur : Mirghani Saeed Mohamed

Université de soutenance : University of Nebraska - Lincoln

Grade : Doctor of Philosophy (PhD) 1994

Résumé
SRN-39 is a recently released sorghum cultivar in Sudan. Understanding the nitrogen (N) and growth patterns are crucial in its adaptation to a N deficient environment of the intensively cultivated regions of Sudan. However, study of N to conserve soil fertility must be coupled with a strategy that minimizes the expenses for N fertilizer. An experiment using a rotation system with and without N fertilization was conducted at Gezira Station, Sudan. The objectives were to evaluate the effect of two relatively new forage legumes, phillipesara clitoria (Clitoria ternata L.) and phillipesara (Phasulus trilobus Ait.), and three levels of N fertilizer on the N content and growth patterns of SRN-39. The results showed that N model parameters of exponential equations were significantly affected by both N levels and preceding crop history. The N uptake of sorghum following legumes was higher particularly during the reproductive period. The response for N levels was higher with the application of the first rate. Previous legumes resulted in an average of 50% increase in sorghum grain yield over monocropping. Continuous sorghum depleted residual nitrate by 28 kg $\rm ha\sp-1$ when no N was applied. Phillipesara and clitoria resulted in 111 and 90 kg $\rm ha\sp-1$ soil nitrate, respectively. A higher sorghum yield and better growth as a result of using clitoria compared to phillipesara as a previous crop indicated other contributions by clitoria. Legume rooting systems, macropores, and soil cracks affected plant N uptake and nitrate accumulation and distribution in the soil.^ Exponential and segmented polynomial exponential models were fitted to dry weight and leaf area, respectively. The inflection point represented the shift from vegetative to reproductive growth. All model parameters were affected by both preceding legume and/or applied N. Net assimilation rate (NAR) and relative growth rate (RGR) responses were not significant although a tendency for legumes to improve these parameters were observed. Differences in crop growth rate (CGR) were attributed to leaf area index (LAI) and leaf area thermal duration (LATD). The environmental stress of 1990 had an effect on dry weight more than the proliferacy of the crop. ^

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