Ground-based, remotely sensed reflectance and temperature data were collected over differentially irrigated, developing cotton and sorghum canopies in order to investigate interrelations of these parameters; to monitor their temporal changes ; to understand their spatial structure ; and to estimate crop coefficient (KO from canopy reflectance. Spectral reflectance and derived vegetation indices showed ability to significantly discriminate among differential irrigation levels of sorghum canopies, starting the fourth week of growth. All vegetation indices increased as a result of crop development, with the perpendicular vegetation index (PVI ) demonstrating the greatest potential for assessing water stress conditions, whereas, soil indices behaved independently of crop development and water stress. Canopy temperature and derived water stress indices, on the other hand, were in high concordance and were able to detect crop water stress with variable degrees of sensitivity. Experimental variograms revealed that cotton reflectance and temperature were not spatially dependent when all water treatments were included. For the moisture stress treatments, only canopy temperature exhibited spatial dependence early in the period of stress. Sorghum canopy reflectance and temperature demonstrated some spatial structure; however, a drift was suspected due to regularity in the data spatial distribution. Normalized difference (ND), normalized perpendicular vegetation index (NPVI) and normalized green vegetation index (NGVI), for fifty days covering the period from planting to heading, were fitted with a complementary error function equation with minor adjustment. Both NPVI and NGVI displayed a 1:1 relation with interpolated tabular values of basal Kc, whereas ND deviated from the 1:1 relation for the period beyond 30 days after planting. The model was also found to be valid for estimating K(c) for moderately deficit irrigation conditions.

No description available.

The West African savanna is characterized by limited and erratic rainfall in one rainy season, increasing degradation of plant and soil resources, a rapidly growing population, and annual food shortages. Zorse is a Kusasi village in Bawku District, Upper Region, northeast Ghana. The Kusasis are intensive farmers of millet and sorghum who live in villages of houses dispersed over the savanna. Surrounding each house is the continuously cultivated field called the saman whose fertility is maintained by annual applications of manure and compost. Field work in Zorse from October, 1978, to March, 1978, included an intensive study of a 50% sample of all houses in the village (n = 126) containing 900 people. In the traditional farming system each household grows and consumes its food as a unit. During the wet season there is a high demand for labor, especially for weeding, but food supplies are at an annual low. In the dry season farming activity is limited to those with dry season gardens. Agricultural development began in earnest in the 1930's but annual food shortages continue to worsen and famine, such as the one in 1976-77 has not been uncommon. Population growth and structure is determined by fertility, mortality, and migration, and reflects the population's relationship to its environment. Population pyramids for Zorse are like those for other areas of the savanna. Their broad bases reflect high mortality and fertility and their skewed sex ratios are the result of excessive outmigration by males 15-45 years old. Migration has been increasing since the beginning of the century and presently about 50% of males 15-45 years old are absent from Zorse and the Upper Region for extended periods of time. Fertility has also been increasing, primarily as a result of decreasing birth intervals, but also as a result of decreasing age at marriage. Birth intervals are controlled by postpartum sexual abstinence. Kusasi couples make the decision to resume intercourse based on the health and development of the youngest child. The shortening of birth intervals reflects the decreased mortality and increased personal security. The pace of social change has increased greatly since the establishment of the British in 1900. The endemic warfare and feuding were stopped and personal security was greatly increased. Public health programs and Western medical treatment were introduced and links with the rest of Ghana and the world were established and began to grow. The savanna environment is fragile and agriculture in Bawku depends on highly variable rainfall of about 1000 mm per year, and on maintaining fertility on the thin, erosion-prone soils. In areas of high population density like Bawku, there is much evidence of soil erosion, loss of soil structure and fertility, and degraded vegetation. The rapid population growth and high emigration rate in Bawku and similar areas of the savanna jeopardize the possibility of improving the food supply. People's decisions about migrating and birth spacing are adaptations to an intensive agricultural system in an environment where productive potential is decreasing under the present system. For the situation to improve it will be necessary for community resources management systems to develop so that demographic and farming behavior by individuals and households will be linked to community well being.

Thesis (PhD)--University of South Australia, 1998

Thesis (PhD)--University of South Australia, 1998

Thesis (M.S. - Renewable Natural Resources)--University of Arizona. / Includes bibliographical references.

Thesis (Ph. D. - Arid Land Studies)--University of Arizona, 1983. / Includes bibliographical references (leaves 147-152).

Thesis (doctoral)--Universität, Hohenheim, 2006. / Includes bibliographical references (p. 187-199).

Thesis (Ph. D. - Arid Lands Resource Sciences)--University of Arizona, 1983. / Includes bibliographical references (leaves 164-170).

Dryland salinity is a major and expanding threat to agricultural land in Australia. Animal production from forages grown on saline land is perhaps its most promising economic use. Glycophytic forage legumes have been evaluated under saline conditions mainly for agronomic characteristics and, to a lesser extent, for nutritive quality to animals. Plant growth and its nutritive quality are interrelated, but a decline in yield in response to salinity may be associated with effects on the chemical constituents of the plant since soil salinity affects plant metabolism. This research aimed to investigate changes in the components of yield and nutritive value of two legumes species. Lucerne ( Medicago sativa ) and Melilotus ( Melilotus albus ) were exposed to different levels of NaCl in the range of 0 to 110 mM NaCl. The research tested the hypothesis that the components of plant nutritive value are not as sensitive to salinity as shoot biomass production since the adaptive mechanisms of the plant lessen harmful effects of the salts. For both plant species, salinity decreased leaf and stem dry matter production, but increased leaf - to - stem ratio. In addition, salinity resulted in earlier flowering in Melilotus. Mineral composition was the most sensitive component of forage quality. Calculated sodium chloride concentrations were up to 125 g / kg DM in lucerne and 39 g / kg DM in Melilotus when irrigated with 110 mM NaCl. The concentrations of calcium and magnesium decreased in both species and approached the marginal range for animal production. Zinc concentration also decreased while potassium decreased in stems of lucerne only. The digestible organic matter ( DOMD ) in response to salinity varied between species. At the highest salt concentration, the whole shoot ( i.e., leaf and stem ) of lucerne decreased up to 4 percentage units while Melilotus increased by 6 percentage units. In lucerne, DOMD was influenced by a high concentration of soluble ash in leaf and stem and, in Melilotus, by an increase in the organic matter content of leaf and a reduction in lignin concentration in stem, which favoured higher digestibility. These results were supported by a histological study in which an increase in starch in Melilotus leaf, and a lower proportion of xylem in relation to parenchyma in stems, was measured. Crude protein concentration was not compromised and, in relation to Melilotus, coumarin concentration did not increase with salinity. In conclusion, the reduction in DM production of species with similar salt tolerance does not necessarily correspond to an equivalent reduction in nutritive value. This research represents the most detailed study into effects of salinity on glycophytic forage legumes. Results show that while some aspects of forage quality ( e.g., minerals composition and energy ) are strongly influenced by salinity, other aspects ( e.g., protein ) remain relatively unaffected. These findings have implications for development of productive grazing systems on saline agricultural land. / Thesis (Ph.D.)--School of Agriculture, Food and Wine, 2006.