Biomass, cover, density, height and concentrations of N, P, C, Fe, Mn, Cu and Zn were evaluated in Sporobolus cryptandrus and Eragrostis lehmanniana at flowering and at seed ripening stage to determine whether these attributes are affected by the type of litter used or by litter treatment. Annual rye, California poppy and rye-poppy mixture were the sources of litter while litter treatments included removing organic residue, leaving organic residue standing or roto-tilling organic residue into the surface soil. The effect of litter type and litter treatment on the soil was evaluated. A parallel greenhouse experiment was carried out. Results indicate that California poppy contained a higher level of all nutrients studied compared to annual rye and contained about twice the concentrations of N, Mn, Zn and Fe. For both annuals and perennials, the nutrient content generally decreased between flowering and seed ripening with annuals indicating more decline than perennial grasses. The greatest decline was observed for N in California poppy. Field observation confirmed that the non-lignified California poppy shoots broke down faster than culms of annual rye. Biomass production in Sporobolus and Eragrostis was unaffected by litter type. However, for both species the highest biomass was obtained in the tilled treatment. Litter tilling produced more vigorous and healthier plants compared to other treatments. Except for P, nutrient concentrations were largely unaffected by litter type. The highest P concentrations were consistently obtained from perennial plants grown in annual rye plots. Fe and Cu concentrations were consistently higher in the tilled treatment. C and P appeared unaffected by litter treatment. N, Mn and Zn concentrations were more variable and more difficult to categorize. In soil samples, all nutrient concentrations were higher at the end of the study than at the beginning. Litter source appeared to have minimum effect on nutrient concentration while tilled treatment was superior to standing which was superior to the removed treatment.

A mathematical model study was made to compare simulated soil temperature variations with a field situation. The study involved the use of two plots, one of which was cleared of all vegetation and the other left in its natural vegetative state. Each plot was watered at the beginning of three different trial periods and as drying occurred, the following atmospheric parameters were measured on an hourly basis: incoming solar radiation, air temperature, relative humidity, cloud cover, and wind speed. The above parameters provided input for solution of the energy budget equation to determine soil surface temperature variation. Using the soil surface temperature variation as an upper boundary condition, and assuming heat movement by conduction, the temperature at 5 cm increments down to 70 cm in the soil was calculated. The two plots provided model testing for a bare soil surface and also for a soil surface beneath a 30 percent and a 40 percent plant cover. Actual and calculated temperature difference was in most cases less than 2°F. The mathematical model is applicable to any area where the above parameters may be monitored.

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Thesis (Ph. D. - Watershed Management)--University of Arizona. / Includes bibliographical references.

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This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.