The influence of the herbicides sulfometuron and simazine on the establishment of 8 species of tree seedlings was studied in northern Israel. The experiment included three treatments and a control. The first treatment applied simazine at a rate of 5 kg/ha, and second treatment applied simazine at a rate of 5 kg/ha and sulfometuron at a rate of 0.03 kg/ha. Sulfometuron was applied alone at a rate of 0.03 kg/ha in the third treatment. Statistical analyses showed significant effects on the survival of some species treated with sulfometuron. To ensure earlier season survival, the rate of sulfometuron applied should be kept at a minimum level to allow both weed control and adequate establishment of seedling. Low-rate applications are particularly important in arid and semi-arid areas.

Many factors influence the salt tolerance of plants. This study investigated the effects of form and concentration of nitrogen fertilizer on the salt tolerance of 'Tifway' bermudagrass grown under four salinity levels in a nutrient solution. The design was a 4 x 2 x 2 factorial in an RCB design. The four salinity levels were 0 (1.6 to 3.6), 10, 22, and 42 dS m⁻¹. Nitrogen was applied in the NH₄⁺ and NO₃⁻ form and at 52.5 and 210.0 mg N L⁻¹ of nutrient solution. The results indicated that NH₄⁺ improved the salt tolerance of 'Tifway' bermudagrass in terms of aesthetic value (color and leaf firing), osmotic adjustment (free amino acid content), and tolerance of specific ion effects (Na, Ca, and the Na:K ratio). The 210.0 mg N L⁻¹ concentration improved the root:shoot ratio of 'Tifway' bermudagrass and reduced salt ion accumulation in shoots.

A two year study was conducted to determine the optimum timing of the initial post-plant irrigation for cotton (Gossypium hirsutum L.). A short-season Upland variety, DPL 20, was planted on 19 April 1993 and 15 April 1994 at the Marana Agricultural Center. Daily midday leaf water potential measurements were taken using the pressure chamber technique. Treatments, designated T1, T2, and T3, received the initial post-plant irrigation when the midday LWP measured -1.5, -1.9, and -2.3 MPa, respectively. Soil-water data was collected at 25 cm depth increments using neutron attentuation. Yields were 1263, 1244, and 1110 kg lint/ha in 1993 and 1229, 1176, and 1095 kg lint/ha in 1994 for T1, T2, and T3, respectively. When treatments were initiated, approximately 84 (T1), 62 (T2), and 32% (T3) of the total plant-available water was present in the upper 150 cm of the soil profile.

Each year the horticultural industry is demanding increasing amount of high quality soilless media. To meet the need this study evaluated coconut coir as an organic component in substrates. Asian and different Mexican coir-based media were compared to sphagnum peat to characterize coir suitability in tobacco transplant growth. These organic components were combined in different proportions with inorganic constituents to create three water holding capacity levels. The organic components, standardized in their capability to hold water, were evaluated by four growth parameters: leaf area, transplant height, dry weight, and total nitrogen concentration. Uncompressed, aged, and leached coir-based media produced transplants equivalent to those produced in peat-based media and were superior to those of either compressed or unleached coirs. Both extreme compression and high chloride concentration appear to affect coir suitability in growing transplants. Two Mexican leached coir and sand combinations produced the highest transplant quality under the conditions of this study.

acase@tulane.edu

The study consisted of six experiments conducted to examine the spectral response of different varieties of corn (Zea mays), squash (Cucurbita pepo) and bean (Phaseolus vulgaris) under variable zinc (Zn), nitrogen (N) and water treatments. Five of these experiments were conducted in the greenhouse during 1988 and 1989. The sixth experiment was conducted in the field during the summer of 1989. Ground-based, remotely sensed data were collected over plant canopies during the growing period, using an Exotech Model 100 AX hand-held radiometer. The Exotech offers filter sets which match the thematic mapper (TM) bands 1 through 4 (0.45-0.52, 0.52-0.60, 0.63-0.69, and 0.76-0.90 μm). Canopy spectral reflectance and derived vegetation indices showed their ability to significantly discriminate among varieties and variable treatments. Soil adjusted vegetation index (SAVI) mimics the normalized difference vegetation index (NDVI) and transformation normalized difference vegetation index (TNDVI) and exhibited all the characteristics of the NDVI curve when there were no soil influences (a single soil type). Red and near infrared (NIR) reflectance factors exhibited ability in monitoring crop growth and development. The TNDVI showed its superiority in detecting variations and in correlating with ground truth data (biomass cover percent). However, the study showed that remotely sensed data were sensitive to variations (varieties and treatments), but the data did not differentiate between them, unless supported with ground truth data.

F2 progeny from crosses between twenty-seven translocations and eleven genetic characters of Sorghum bicolor (L.) Moench were studied to demonstrate the use and limitations of translocations in mapping genes on chromosomes in this species. A summary of results from 1976 to 1989 is reported using temporary chromosome designation letters A to J. Recombination was estimated between translocation breakpoints and loci for six simply inherited traits. Inferences from linkage data indicate Zbzb to be located on chromosome F; Slsl on chromosome B; Yy (and linkage group 4) on chromosome J; Lglg and Pp (and linkage group 2) on chromosome C; and Bm0, on either A or B. Semisterility of three translocations was found to be linked with genes from two different linkage groups: T-16(FJ) with both Zbzb and Yy; 9157 (BF) with both Zbzb and Slsl; and T-10(CB) with genes Lglg, Pp and Slsl.

This study was designed to explore correlations between flower and seed characters and the relationship of flower and seed characters to yield. Thirty six lines selected from Composite Cross XXXII material were planted in a randomized block design with four replications. At anthesis, spikes from each plot were collected and fixed in 70% alcohol. At the same time, an equivalent spike was tagged to be harvested at maturity. Measurements of flower characters were made on the preserved spikes and seed. Length, width and weight were obtained on the mature spikes. Flower volume was calculated by multiplying the area of lemma and palea by flower thickness. Correlations indicated that selection for flower characters at anthesis would be an effective selection technique for seed characters.

There are thousands hectares of abandoned farmlands in Arizona. Research on practical methods for establishing native plants and wildlife on abandoned farmlands is under way at the Desert Botanical Garden of Phoenix and the University of Arizona. This research is aimed at improving understanding of the primary variables affecting restoration of abandoned farmlands. These variables include: water treatments, planting dates, mulch and water catchment, seasonal planting and plant species composition. The objectives of the study is to investigate the effect of land restoration practices on nitrogen, protein, fiber (NDF and ADF), ash and dry matter contents of three Atriplex species under different management and site conditions. The amount of nutrient contents in Atriplex species growing on abandoned farmlands under irrigation and conservation practices is higher when compared to no irrigation or control in Casa Grande research site. Atriplex species growing under mulch and water catchment condition had significantly higher nutrient content compared to other treatments. Furthermore, seasonal planting in abandoned farmlands affected the nutrient contents of Atriplex cultivars at the University of Arizona farm. The Atriplex cultivar planted in the winter had higher nutrient contents when compared to those planted in the summer and irrigated with a sprinkler irrigation system for some cultivars. A better understanding of how these variables affect nutrient contents of Atriplex species used in this restoration study will play an important role in directing public interest towards the revegetation of abandoned farmlands in southern Arizona for food production.

In an effort to determine the agronomic necessity of K fertilization of cotton (Gossypium spp.) in Arizona, a five-year study was initiated in 1991, with a single field study near Gila Bend. Subsequent sites selected ranged from western (Yuma) to eastern (Safford) Arizona which totaled 11 site-years. Both Upland (G. hirsutum L.) and Pima (G. barbadense L.) cottons were cultivated, using soil and foliar applications of K. In 1992, study sites included the Safford Ag. Center (SAC), Maricopa Ag. Center (MAC), and a fanner cooperator site at Coolidge. In 1993, the experiment stations (SAC and MAC) were continued and Yuma Valley was added. The 1994 sites included only the experiment stations (SAC and MAC). In 1995, SAC and MAC were again maintained and a third location, a fanner cooperator site at Buckeye was added. Results from the study (12 site-years) indicated no lint yield increases due to K fertilization in all locations with either Upland or Pima cotton However, in 1995 at Buckeye, the result revealed a significant yield reduction due to the K foliar treatments. There were, however, no significant differences among the soil-only or the soil- plus-foliar treated plots at this location. Potassium (K) release kinetics of clay samples from 10 agricultural representative soils of Arizona was determined by successive extraction using a Ca-saturated cation resin. A preseason physical and chemical characterization of the soils showed all soils contain smectite-mica minerals. Four mathematical models (power function, Elovich, parabolic diffusion and first-order) were used to describe the nonexchangeable K release reaction involving 700-hour cumulative extraction time. Comparison of the models using the coefficient of determination (r²) and the standard error of the estimate (SE) indicated that the Elovich and the power function equations overall displayed the best fit. The first-order, and for the most part, the parabolic diffusion equation did not describe the K release very well. The constants a (initial rate) and b (release rate) for the Elovich and the power function equations, are at least in the order of magnitude as those found by others in several previous studies.