Search Results
Abstract
This study was initiated to establish critical N plant tissue levels for asparagus (Asparagus officinalis L.) during the fern growing season. Tissue samples for chemical analysis were taken from asparagus plants over three growing seasons. The experiment consisted of nine treatments with five levels of water ranging from 750 to 4200 mm·ha−1 and five levels of N fertilizer ranging from 100 to 655 kg N/ha. Only the cladophylls were sampled during the fern growing season beginning in mid-April and monthly through mid-September. Total N concentration at various sampling dates and spear yield were highly correlated. Total N concentration indicated the N status of the asparagus plant. Minimum or critical levels of total N were established for the fern growing season in the desert regions of Arizona.
Six field studies were conducted from 1980-88 to evaluate the response of cabbage (Brassica oleracea L., Capitata group) to sprinkler irrigation and sprinkler-applied N fertilizer on a coarse-textured soil. The plots were irrigated using a modified self-moving lateral sprinkler irrigation system that applied five levels of water and five levels of N (liquid NH4NO3) in specified combinations of central composite rotatable design. Cabbage yields were significantly increased by water and N applications in all experiments. The N rates predicted for maximum yield exceeded typical cabbage N fertilizer recommendations. However, the above-average plant populations used in these studies resulted in above-average yields and plant N accumulation. Deficit and excess irrigation produced negative results. Generally, cabbage production was optimized and N losses to the environment were minimized when crops were irrigated for evapotranspiration (ET) replacement. However, even when irrigated for ET replacement, these data demonstrate the potential for N leaching at high N rates, presumably as a result of rainfall.
Mature `Campbell Nucellar Valencia' trees were converted from border flood irrigation to four pressurized irrigation systems. A border flood irrigation treatment was included as a control. Four years later, roots were collected from 62 holes (10 cm diameter × 120 cm) on a 60 cm grid on one side of each treated tree. For trickle irrigated trees, the highest concentration of roots was found around the emitters, particularly at 30 to 90 cm deep, but some roots appeared to be located below the 120 cm depth. Root distribution was similar for the basin irrigated trees, but the highest concentration of roots was found in a larger wetted area near the tree trunk. This treatment had the highest root concentrations, compared to all other treatments. Root distribution of trees irrigated by spray irrigation was similar to the basin treatment, except that root spread was not as extensive. Roots of trees irrigated by sprinkler and flood were distributed more randomly, and were more likely to extend past the drip line, compared to the other treatments. Root concentrations also declined with increasing depth.
A study was conducted during four seasons to evaluate the performance of mature `Valencia' oranges converted to pressurized irrigation systems. Trickle, bubbler, spray, and sprinkler systems were all compared to the traditional flood-border irrigation. During the second year after conversion, trees irrigated by flood grew significantly more than trees irrigated by any of the pressurized systems. However, there were no differences in tree growth during the third and forth year, suggesting that the trees adapted to the new irrigation systems. Effects of irrigation treatments on leaf concentrations of N, P, Fe, Zn, Mn, and Cu were minimal. There were significant differences in orange yields among the irrigation treatments within years. However, average or total yields over the four year period did not vary by irrigation treatments. Similarly, there were no consistent differences in fruit or juice quality. Overall, results from this study indicate the mature citrus can be converted to pressurized irrigation systems with minimal effects on fruit yield and quality.
A study was conducted during four seasons to evaluate the nutrient requirements of `Valencia' oranges converted from flood to a pressurized spray irrigation system. The experiment was a 3×2×2 factorial with 3 N rates (0.34, 0.68, and 1.36 kg/tree/year), 2 P rates (0 and 0.11 kg/tree/year) and with and without added micronutrients (Fe, Zn, Mn, and Cu). There were no growth or yield responses to micronutrients. Phosphorus fertilization increased fruit yield, improved juice quality, and reduced peel thickness. There were trends for N to reduce juice quality and increase peel thickness when P fertilizer was not added. Tree growth increased by N fertilization only the first season after conversion. Fruit yield also increased by N but only when P was added. Leaf tissue N concentrations increased with time during the first two years within N treatments. These data suggest that the higher rates of N may only be needed initially after conversion as the tree roots adapt to the new irrigation system.
Field studies were conducted to develop water and N response surface models for broccoli and cauliflower (Brassica oleracea L., Botrytis Group) produced in the low desert of the southwestern United States and to estimate profit maximizing combinations of water and N over a range of realistic price situations. Marketable broccoli and cauliflower yields were increased by water and N inputs in all experiments. Generalized response equations indicate maximum broccoli yields with 43 cm of water and N at 267 kg·ha–1 and maximum cauliflower yields with 65 cm of water and N at 338 kg·ha–1. Least-cost combinations of water and N changed with the costs of these inputs for yield levels below the economic maximum. However, profit maximizing N and water rates changed little regardless of input or crop prices investigated.
Whole-tree branch architecture was quantified by counting and measuring the lengths of main stems, basal branches, and all primary (1°), secondary (2°), and tertiary (3°) branches. Trees were grown in replicated clonal plantations established in 1991 on a southern Illinois lowland and an upland site. Fifty-two clones in each of five complete blocks were measured from each plantation. Number of primary branches that formed in 1991, 1992, and 1993, and the number of nodes in the terminal meter of growth were highly significant for silver maple provenance and for clones (four clones for each of 13 provenances), except that clonal differences were nonsignificant for the number of 1° branches on 1991 wood. There were significant effects of provenance and clone on total number and the various sizes of 2° and 3° branches. Generally, a greater number and longer length of 2° and 3° branches formed on trees from the more rapidly growing southern provenances.
Abstract
Regreening of ‘Valencia’ oranges (Citrus sinensis L., Osbeck) is more intense with trickle irrigation than flood irrigation. Peels of fruit from trickle-irrigated trees contain more chlorophyll and less carotenoids than peels of fruit from flood-irrigated trees. Peels of ‘Redblush’ grapefruit (C. paradisi Macf.) from trickle irrigated trees have higher chlorophyll and lycopene contents, but do not differ in ß-carotene content.