Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → États-Unis → 1980 → ANALYSIS OF PRODUCTION POTENTIAL AND MAINTENANCE OF PRODUCTION FOR SELECTED IRRIGABLE SOILS BY THE CHARI RIVER IN THE SAHEL REGION OF CHAD

Cornell University (1980)

ANALYSIS OF PRODUCTION POTENTIAL AND MAINTENANCE OF PRODUCTION FOR SELECTED IRRIGABLE SOILS BY THE CHARI RIVER IN THE SAHEL REGION OF CHAD

KING, JACK WINFIELD, JR

Titre : ANALYSIS OF PRODUCTION POTENTIAL AND MAINTENANCE OF PRODUCTION FOR SELECTED IRRIGABLE SOILS BY THE CHARI RIVER IN THE SAHEL REGION OF CHAD

Auteur : KING, JACK WINFIELD, JR

Université de soutenance  : Cornell University

Grade : Doctor of Philosophy (PhD) 1980

Résumé
During the 1970’s there were several attempts to establish irrigated agriculture on the alluvial soils along the Chari and Logone rivers in the Chad basin south of N’Djamena. Inconsistent responses to nitrogen, phosphorus and potassium, and, in some cases, rapid declines in yield indicated a need for a study of both the production potential of soils of this region and of cultural systems which would maintain satisfactory yields. In the primary experiment field experiments with irrigation were conducted starting with the first cropping season on newly developed lands. Response to nitrogen, phosphorus and potassium and the effect of hyacinth bean (Lablab purpureus) in a rotation with irrigated sorghum were tested on two soils. One was a light upland soil of the type traditionally used in this region for rainy season millet production. The other, lower in the topography, was a clay soil of the type traditionally used for winter sorghum production. Because of problems with emergence the first three trials did not produce significant results. After a procedure involving transplanting young sorghum plants was used at two new but similar locations significant results were obtained. This experiment was set up in a randomized complete block design. There were six replications of five treatments : 0-0-0, 0-240-240, 480-0-240, 480-240-0, 480-240-240, at the two locations. Sorghum crops were harvested in the fall of 1978 and the spring of 1979. There were responses to the three macronutrients and to the rotation with hyacinth bean which had the effect of compensating for missing nitrogen and phosphorus in treatments where these nutrients were not applied as inorganic fertilizer and reducing the availability of potassium. In the first of two secondary experiments samples were taken across three typical soil series at the project site. The precise location and elevation of each sampling site was established by means of a transit and a level. Samples were taken to a depth of 140 cm with the soil from twenty centimeters being included in each sample. Analyses were made for organic matter, pH, P, K, Mg, Ca, Mn, Fe, Al, NO(,3), NH(,4), and soluble salts. The nutrient status of these soils was then characterized relative to their location in the topography. The same set of analyses were performed for the second of these experiments which was designed to compare the effect of traditional agriculture with that of a long-term fallow. Near the project about 50 hectares of land which had not been cleared for forty years lay next to, and on the same soil type as, an area which had been used for winter sorghum production for 10 years. Six random transects were made perpendicular to the fenceline dividing the cleared and forested land. Samples were taken at twenty-five meter intervals to a distance of 100 meters on each side of the fence. At each sampling site, three samples each taken from fifteen centimeters of soil were collected making a total of 45 cm of surface soil tested. The results of this experiment showed that the soil which was forested had larger quantities, at least at one depth of OM, K, Ca, NH(,4), and soluble salts as well as a higher pH than the cleared land but the results for Ca and soluble salts could not be explained relative to differences in land use. The cleared land had a higher Fe content than did the forested land.

Proquest Dissertations & Theses

Google books

Page publiée le 12 février 2015, mise à jour le 18 octobre 2019