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  • Author or Editor: W. D. Pew x
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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.

Open Access
Authors: and

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.

Open Access
Authors: and

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

Abstract

Comparisons were made between urea, NH4NO3, (NH4)2SO4 and several controlled-release N (CRN) fertilizers on spring-grown lettuce (Lactuca sativa L.). In 1980 and 1981, single applications of CRN fertilizers produced high yields of excellent quality lettuce. In 1980, the largest yield with the most 2-dozen and fewest 2½-dozen size heads (24 and 30 heads/carton, respectively) came from lettuce receiving methylene urea (MU) F2950 at 168 kg N/ha preplant plus 84 kg N/ha as urea at folding stage. However, the yields from lettuce fertilized with this combination were not significantly different from those of lettuce fertilized with a single application of sulfur-coated urea (SCU) F9999 at either 252 kg N/ha preplant or 168 kg N/ha at thinning stage. Lettuce fertilized with urea applied at 168 kg N/ha preplant produced relatively low yields. Lettuce fertilized with urea at 168 kg N/ha in 3 applications of 56 kg N/ha each produced significantly higher yields than when the crop received urea at 168 kg N/ha preplant, but the extra applications were costly and time consuming. In 1981, lettuce fertilized with CRN sources at 224 kg N/ha preplant was earlier maturing than when fertilized with any common soluble N material at the same rate. The data show that CRN fertilizers could be helpful in reducing fertilizer application costs and keeping crop production profitable.

Open Access

Abstract

Urea, ammonium nitrate (NH4NO3), and several controlled-release N (CRN) fertilizers were compared as sources of N for head lettuce (Lactuca sativa L.). CRN fertilizers varied widely in their effectiveness. Materials with the fastest N-release characteristics gave the poorest results when applied preplant. Effectiveness of some slow-release materials depended on time of application. Neither NH4NO3 nor urea were good sources when applied preplant but were effective in 3 equal 56 kg N/ha applications throughout the season. Methylene urea (MU), F2950, was most effective when applied 30 days after planting. Sulfur-coated urea (SCU), F9999, produced the most vigorous seedlings and plants with the greatest uniformity and harvestable heads with earliest maturity, best head size, and color.

Open Access