No description available.

No description available.

Two field studies were conducted during the 1993-1994 season to evaluate the response of lettuce to soil applied amendments. Treatments included gypsum, polymaleic acid (Spersal), and two acid products (N-phuric and Phos-phuric). Gypsum rates (0, 2240, and 4480 kg /ha) were the main plots and other soil amendments were subplot randomized within the mainplots. Overall, gypsum reduced early growth and vigor of lettuce. Gypsum had no effects on marketable yield and quality parameters in experiment 1, but the highest gypsum rate (4448 kg /ha) decreased marketable yield in experiment 2. There were no differences in plant stands due to subplot treatments. However, there were differences in earlygrowth and vigor. In experiment 1, both "N-phuric" and "Phos-phuric" increased early lettuce growth compared to the control. In experiment 2, Phos-phuric was superior to N-phuric. In experiment 1, the benefits of early growth and vigor to the "N-phuric" and "Phos-phuric" carried to harvest where marketable yield and quality were significantly increased. Spersal did not significantly effect yield and quality of lettuce in either experiment.

Lettuce produced in the desert typically shows large yield responses to N fertilization. However, concern about the potential threat of nitrate-N to ground water has prompted additional studies aimed at developing improved N management practices. Field experiments were conducted between 1992 and 1994 to evaluate the response of iceberg lettuce to N rate and N management practice. The use of controlled release N sources (CR19 were compared to a soluble N fertilizer applied preplant (PP), and a soluble N fertilizer applied in split-sidedress applications (SD). Rates of N fertilizer application ranged from 0 to 300 kg ha⁻¹. Lettuce generally showed significant responses to N rate and N management practice. However, response to management practice varied by site-season. When conditions for N losses were high, SD and CRN management strategies were superior. However, in other site seasons SD management sometimes resulted in inferior head quality and marketable yield when compared other management strategies. Data averaged over six -site seasons shows improved yield and quality to CRN management strategies compared to PP and SD strategies. Although the controlled-release fertilizers used in these experiments cost three times more the conventional soluble sources used, preliminary analysis shows the use of CRN strategies would sometimes be economically favorable.

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.

No description available.

No description available.

The use of stylet oil to slow the spread of the whitefly- transmitted vines, lettuce infectious yellows, shows sufficient promise to plan for expanded research efforts. The main positive results were a slower buildup of virus infection and a larger number of marketable heads in the block of lettuce sprayed with oil. Weight (in grams) of individual heads could be correlated with time of infection in that the lowest weights and marketability ratings occurred in plants infected earliest in the season. Whether they were front treated or untreated plots, marketable heads weighed an average of 784 grams; unmarketable heads weighed 491 grams. The key difference is that, on the average, five marketable heads of lettuce were in the oil- treated plots for every three in the untreated plots. A follow-up experiment will be conducted in 1989 to determine if these preliminary positive results indicate that stylet oil treatment may be a practical control method for slowing the spread of L1YV.

Leaf drop of lettuce, caused by Sclerotinia sclerotiorum, is a sporadic, but destructive, disease in Arizona. Field trials were established during 1987 and 1988 to evaluate potential new fungicides for disease control. Ronilan and Rovral, the two materials currently registered for use on lettuce for Sclerotinia leaf drop, were consistently among the most effective fungicides for disease control. Levels of disease control equivalent to that provided by Rovral and Ronilan were observed with CGA-449, SC-0854 SDS-65311, Bay HWG 1608, and Spotless. These field tests have identified several potential new fungicides for control of leaf drop of lettuce caused by S. sclerotionan.

No description available.