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Open access

B. R. Gardner and R. L. Roth

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.

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B.R. Gardner and C.A. Sanchez

Lettuce is planted in the southwestern U.S. desert from September through December and harvested from November through April each year. During this period mean soil temperatures range from 7 to 30C. Lettuce produced on desert soils shows a large yield response to P. Soil solution P is replenished by desorption from the labile soil P fraction and this process is temperature sensitive. A field study was conducted over 6 years to evaluate the response of lettuce to soil solution P levels under different ambient soil temperature regimes. The soil temperatures under which lettuce was grown were varied each year by altering planting dates. Soil solution P levels were established and maintained each season using P sorption isotherm methodology. Lettuce responded to P in all experiments. Phosphorus levels required for maximum yield varied with each experiment. Soil P levels required for optimal yield were best correlated to mean soil temperatures during the last 20 days before harvest. Lettuce accumulates over 70% of its P during the heading stage of development and it is likely that during this period of rapid growth and nutrient uptake, solution P becomes limiting when soil temperatures are cool.

Open access

W. D. Pew and B. R. Gardner

Abstract

A preplant N application and the 2 irrigation methods most commonly used in Arizona to germinate commercially grown lettuce (Lactuca sativa L.) were studied in relation to the movement of soil NO3-N and total soluble salts (TSS) in lettuce beds. The intermittent pattern of irrigation resulted in highest levels of TSS at all sampling depths two weeks after the germination and emergence of the lettuce. Total soluble salts and NO3-N concentrations were increased by irrigation and were greatest in the surface 5 cm and center of the bed. Nitrogen application increased the amount of NO3-N found in the lettuce beds. Neither irrigation nor N treatment caused any accumulation of NO3-N in the area of the beds where the lettuce seedlings usually grow. The distribution patterns indicate that preplant N applications would be ineffective in meeting the early N needs of the plants.

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B.R. Gardner, R.L. Roth, and C.A. Sanchez

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.

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G. C. Wright, R. L. Roth, and B. R. Gardner

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.

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R.L. Roth, B.R. Gardner, and C.A. Sanchez

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.

Free access

C.A. Sanchez, R.L. Roth, and B.R. Gardner

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.

Open access

W. D. Pew and B. R. Gardner

Abstract

Higher yields, larger fruit size, and earlier maturity were achieved in muskmelons (Cucumis melo L.) by irrigating when soil moisture tensions at the 25-cm depth reached 50 and 75 kPa compared with tensions of 25 kPa. More fruits were culled in the wet treatment due to decay while the drier treatments produced more fruits with growth cracks. Melons from the drier treatments were higher in soluble solids. Irrigation did not affect the other storage and shipping quality factors measured. A prethinning irrigation caused restricted root development, vine growth, fruit size, and yield.

Open access

B. R. Gardner and W. D. Pew

Abstract

The effectiveness of ammonium nitrate, ammonium sulfate, calcium nitrate and urea for winter grown head lettuce (Lactuca sativa L.) was evaluated. N source did not affect yield, quality factors, head size or total N accumulation. Applications of fertilizers containing NO3-N resulted in slightly higher NO3-N concentrations in the midribs. Plant growth and N accumulation were similar with all N sources at low temperatures. Air temperature below 13°C for a week or more sharply reduced N uptake and plant growth with all sources. About 80% of the total N is taken up by the plants in the 4 weeks before harvest. N source did not affect quality.