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University of Gezira (2009)

LAND DEGRADATION AND SORGHUM PRODUCTIVITY ASSESSMENT USING SPATIAL ANALYSIS AT GADAMBALYIA SCHEMES, GADAREF STATE, SUDAN

AHMED, HANAN OSMAN ALI

Titre : LAND DEGRADATION AND SORGHUM PRODUCTIVITY ASSESSMENT USING SPATIAL ANALYSIS AT GADAMBALYIA SCHEMES, GADAREF STATE, SUDAN

Auteur : AHMED, HANAN OSMAN ALI

Université de soutenance : University of Gezira

Grade : DOCTOR OF PHILOSOPHY IN SOIL SCIENCE (2009)

Résumé
One of the most important recent issues facing Sudan as well as sub-Sahara Africa is the threat of continued land degradation and desertification. Land degradation is a serious problem that crosses national borders, ecological zones and socio-economic levels. It can be especially devastating for the world’s poorest people living in dryland areas. The need for spatial and temporal land degradation detection over a larger scale makes satellite imagery the most cost effective, efficient and reliable source of data. The applicability of GIS makes it an important and efficient tool for land degradation. In this study Satellite images and GIS were integrated with soil data, field survey and climatic factor to evaluate land degradation in Gadambalyia schemes, Gadaref State, Sudan. Therefore, this study is intending to detect the type, assess and map the degree of land degradation in Gadambalyia schemes of Gadaref state by using spatial analysis. The goals of this study are to assess land degradation and yield reduction. The type and degree of land degradation was assessed through analyzing and mapping soil quality, agricultural practices and climatic factors. The soil quality including some physical (BD, clay percent, AWC, FC and HC) and chemical indicators (TN, pH, CEC, OC and Cl) taken in 2005 were laboratory analyzed and SIRIS method was used for soil degradation classification and compared with the same indicators which were obtained in 1976. The management practices including farmer and its farm such as education level, age, work beside agriculture, financial support, weed control, seed source and sowing dates for sorghum were collected during the field survey. Climate factors for Gadaref, Gadambalyia and Elhori were investigated through rainfall characteristics, evaptranspiration and aridity index for the period from 1981 to 2005. The climate data obtained from Sudan Metrological Authority (SMA), State Ministry of Agriculture and Animal Wealth and the Mechanized Rainfed Corporation (MFC). The sorghum yield data were obtained from MFC for the period from 1981 to 2005. The results revealed that the soil qualities in 2005 were significantly affected (P≤0.001) negatively and positively, compared with 1976. The results showed soil chemical degradation ranging from a low to a severe degree of degradation. The field survey showed that more than 88% of the sampled farmers were in the active age (20 -60 year) and about 73% attained some sort of education. About 28% of them managed their farms and 39% taking agriculture as a permanent job. About 76% of sampled farmers were taking sorghum seeds from previous production and 59% were sowing sorghum in July and 36% in August and 2% in mid June (early sowing) and 2% in September ( late sowing date). The median for rainfall Gadaref, Gadambalyia and Elhori were 584mm, 520mm and 463mm respectively. The large number of deviated years from the median were obtained by Gadambalyia (64%) followed by Gadaref (44%) and the lowest was Elhori (36%). The trend of long- term annual and monthly rainfall was positive for Gadaref, Gadambalyia and Elhori but the results were not significant. The Cumulative Rainfall Departure (CRD) for Gadaref, Gadambalyia and Elhori did not have a regular trend. The long-term annual evapotranspiration for Kilo 6, Gadambalyia and Elhori decreased with a negative trend but not significant. The long-term monthly (June-October) trend was negative and highly significant (P≤0.001). The long –term annual aridity index for the three stations were increased significantly (P≤0.01), except for the dry years namely 1984 and 1990. The correlation between long- term annual effective rainfall and long -term average sorghum yield was positive but not significant except for Gadambalyia which was significant (P≤0.02). The correlation between evapotranspiration and sorghum yield were negative highly significant (P≤0.01) for the three stations. The PVI classification using decision tree produced four classes namely bare soil, sparse, medium and high density. The bare soil represented 1% of the study area, 35% sparse crop, 40% medium crop density and less than 25% of the area was with high crop density. The Shannon’s Diversity Index (SDI) and Shannon Evenness Index (SEI) indicated that sorghum in the study area and within each farm was heterogeneous. The cause and acceleration of land degradation resulted from Soil mining, unfavoubrable agricultural management practices and climatic factors. This study reached with some valuable conclusion and recommendations which could contribute positively in improving sorghum yield through reducing land degradation processes at Gadambalyia schemes of Gadaref State, Sudan.

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