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M.A. Maurer and K. Umeda

A field study was designed to determine the effect of planting date and cultivar on growth and yield of strawberries in the low desert. The study was conducted at the Univ.of Arizona, Citrus Agricultural Center, near Waddell. Treatments included two strawberry cultivars (Camarosa and Chandler) and three planting dates 20 Aug. and 8 and 22 Oct. 1997. There was no significant difference in fruit yield between cultivars. However, fruit number was significantly greater for `Chandler', and, therefore, fruit size was smaller than `Camarosa.' Yield was significantly higher for strawberries planted 20 Aug., with nearly four times the yield compared to the other planting dates. Results of this study suggest summer planting of strawberries in the low desert to produce economically viable yields.

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M.A. Maurer and M.E. Matheron

A field study was conducted near Mesa, Ariz., in a mature lemon grove with reset `Lisbon' lemon trees (Citrus limon) on a Carrizo citrange rootstock to determine the effects of stump removal and preplant soil fumigation on reset tree growth and development. Treatments consisted of resets planted with or without tree stumps and in addition with or without preplant Vapam. Pretreatment soil samples average 2.1 propagals of Phytophthora per gram of soil; however, after Vapam treatments, Phytophthora was not detected in the treated plots. In subsequent soil sampling for 2 years, Phytophthora was detected in only one plot treated with Vapam. Tree growth and vigor was greatest for resets that had stumps removed and preplant Vapam followed by resets with stumps present and preplant Vapam based on visual ratings and trunk diameter measurements. In addition, resets without stumps were more vigorous than resets where stumps were present.

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M.M. Gaye and A.R. Maurer

Field studies were conducted to determine the effects of row covers (no row cover or Agryl P-17), seeding date, and seeding method (seeding in a furrow or into a smooth soil surface) on the development, harvest date, and yield of brussels sprouts [Brassica oleracea L. (Gemmifera Group)] grown in southwestern British Columbia. The treatments were applied to the plants in the seedbed after which the plants were transplanted in the field and grown to horticultural maturity. In both years, row covers increased soil temperatures and advanced seedling development and transplanting dates compared with uncovered treatments. Leaf weight ratio (LWR) decreased, specific leaf area (SLA) increased, and leaf area ratio (LAR) was unaffected by the application of row covers. Early seeding also promoted early transplanting. In 1987, plots were harvested when plants reached horticultural maturity. There was a linear effect of seeding date on harvest date, early seeding promoted an early harvest, and row covers advanced the sprout harvest of plants seeded earliest (24 Mar). In 1988 all treatments were harvested from 17 to 19 Oct. and marketable yield was improved by early seeding and by row covers. Seeding method did not influence plant growth or yield.

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M.A. Maurer and F.S. Davies

Field studies conducted over two growing seasons were designed to study the effects of reclaimed water on the development of 1-and 2-year old `Redblush' grapefruit trees (Citrus paradisi Macf.) on Swingle citrumelo rootstock. Experiments were conducted at two locations on Kanapaha and Arredondo fine sands and treatments were arranged in a 3×3 factorial experiment. Treatments included reclaimed water, well water plus fertigation and reclaimed water plus fertigation, which received <0.023, 0.23 and 0.23kg N/tree/yr in 1990, and <0.034, 0.34 and 0.34kg N/tree/yr in 1991, respectively. In addition irrigation was applied at 20% soil moisture depletion, 1.5 cm/wk and 2.5 cm/wk for 31 weeks in 1990 and 39 weeks in 1991. Tree growth and vigor were greatest for the reclaimed water plus fertigation based on visual ratings and trunk diameter measurements and lowest for reclaimed water alone, where leaves exhibited visual signs of N deficiency. No differences in tree growth or vigor were observed among irrigation rates. Similar results were observed at both experimental locations.

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M.A. Maurer, F.S. Davies, and D.A. Graetz

A field study was conducted on mature `Redblush' grapefruit trees (Citrus paradisi Macf.) on sour orange (Citrus aurantium L.) rootstock from 1991 to 1993 near Vero Beach, Fla. on poorly drained (flatwoods) soil to determine the effects of reclaimed water on leaf, soil and shallow well-water nutrients. Treatments consisted of a canal water applied based on soil moisture depletion, and reclaimed water applied at 23.1, 30.7 and 36.6 mm/wk. Reclaimed water treatments received supplemental fertilization in addition to the N present in the water. All treatments received about 130 kg/ha/yr N. Leaf tissue N, P, K, Ca, Mg and Na concentrations were similar for all treatments, but B concentrations were significantly higher for the reclaimed water treatments in 1991 and 1993. Soil P and Na concentrations also increased in the reclaimed water treatments. Water samples taken from shallow depth wells showed that reclaimed water treatments had lower levels of NO, compared to the control possibly due to leaching. Reclaimed water contained only trace or undetectable levels of heavy metals.

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T.L. Weinert, S.A. White, T.L. Thompson, and M.A. Maurer

Citrus production in the southwestern U.S. is highly dependent on inputs of irrigation and N fertilizer to achieve optimum fruit yield and quality. Microsprinkler irrigation may allow for substantial increase in efficiency of N and water application. However, best management practices have not yet been developed for microsprinkler use, particularly on newly established citrus trees. Experiments were conducted during 1997–98 in central Arizona to evaluate the effects of various N rates and fertigation frequencies on growth and N partitioning in young `Newhall' navel oranges planted in Apr. 1997. Two experiments were conducted, each with factorial combinations of N rate and fertigation frequency. In one experiment, non-labeled N fertilizer was used and in the other 15N-labeled N fertilizer. Trunk diameter, leaf N, and 15N partitioning in the trees were measured. During 1997, neither trunk diameter or leaf N were affected by N rate or fertigation frequency. No more than 6% of the N applied was taken up by the trees, and about 50% of the fertilizer N taken up was found in the leaves. Trees grew much more rapidly in 1998. Leaf N in fertilized plots was significantly higher than in control plots, but leaf N in all trees remained above the critical level of 2.5%. Despite rapid tree growth during 1998, no more than 25% of the fertilizer N applied was taken up by the trees. About 60% of the fertilizer N taken up was found in the leaves. Results suggest that N applications are not needed during the first growing season after planting for microsprinkler-irrigated citrus trees in the Southwest. Only modest rates (68 to 136 g/tree) will be needed during the second season to maintain adequate tree reserves.