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Mongi Zekri and Robert C.J. Koo

Controlled-release sources of N and K were compared with soluble sources on young `Valencia' orange trees (Citrus sinensis [L.] Osb.). The effects of these fertilizers on leaf mineral concentration, soil chemical analysis, and tree growth were evaluated for 3 years. Soluble fertilizers were generally more readily available but had shorter residual effects on leaves and soil than controlled-release fertilizers. In the top 30 cm of soil, the plots treated with controlled-release N had 23% more total N than those treated with soluble N sources, while the plots fertilized with controlled-release K contained 56% more extractable K than those that received soluble K. Different effects on leaf and soil N between the two controlled-release N sources, sulfur-coated urea (SCU) and methylene urea (MU), were also found. With the use of controlled-release fertilizers, application frequency was reduced from a total of 15 to six applications with no adverse effects on tree growth, leaf mineral composition, or soil fertility during the first 3 years. Combining soluble and controlled-release fertilizers in a plant nutrition program offers an economical and effective strategy for citrus growers.

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H.C. Bittenbender, N.V. Hue, Kent Fleming, and Hilary Brown

A fertilization experiment, started in 1989, evaluated the merits of macadamia husk-manure compost as fertilizer for the production of macadamia. Three fertilization treatments were compared at four sites over 4 years on the MacFarms of Hawaii Honomalino orchard. The treatments were conventional fertilization, a combination of solid and liquid mineral fertilizers annually adjusted by the orchard manager based on leaf and soil analysis; compost only as 5 tons of a macadamia husk-cattle manure compost applied annually between July and October; and compost plus supplemental mineral fertilizers deemed needed by the orchard manager based on leaf and soil analysis. In-shell nut and kernel yield and quality was not significantly different between treatments. Change in leaf nutrient values appears minimum except for slightly lower N at two sites for the compost treatment. Higher Mg was noted for the compost but not the compost plus treatments at the irrigated sites. The effect of compost on the soil nutrient levels was more distinct and may have a delayed and longer term effect. Total exchange capacity of the soil increased, as did soil pH, Ca, Mg, K, and Na. Organic matter increased only at the site with least soil. Extractable soil Fe decreased, this maybe related to the change in pH, but had no consistent effect on leaf Fe. Compost fertilization was not considered sustainable as the cost of compost and its application exceeded conventional fertilization.

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Ray E. Worley and Ben G. Mullinix

After 10 years, application of 112 kg N/ha, divided into four annual applications and applied through the drip irrigation system (fertigated), provided nut yield and quality as good as 224 kg·ha–1 all broadcast or 1/2 fertigated and 1/2 broadcast. Leaf N was well above the 2.50% deficiency threshold. Treatment rates were halved for six additional years with no detrimental effects on yield and quality from fertigation. All treatments still provided leaf N well above the deficiency threshold. After 16 years of N fertigation there appears to be no serious reduction of pH or flushing of other nutrients from the wetted zone of the emitter. Leaf and soil analysis indicate a loss of Ca and Mg in the area away from the emitter when N was broadcast. Soil pH and nutrients were lower in the wetted zone of the emitter than in the area not wet by the emitter, and soil pH, K, and Mg were reduced in the 15- to 30-cm layer with fertigation. Leaf nutrient concentrations reflected the cation concentrations in the nonwetted area. Broadcast N was from NH4NO3 and fertigated N was from URAN (16% N from NH4NO3 and 16% N from urea).

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Russell Galanti, Alyssa Cho, Amjad Ahmad, and Javier Mollinedo

nitrogen concentration using a chlorophyll meter and vis-near infrared multispectral camera HortScience 47 955 960 Hirae, H. 1976 Leaf and soil analysis in macadamia. Hawai‘i Macadamia Producers’ Assn. 16 th Annual Proc. 65 Loh, F. Grabosky, J. Bassuk, N

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Timothy K. Broschat

and african oil palm have been significantly improved with Cl fertilization in the Philippines ( Magat et al., 1988 ; Ollagnier and Ochs, 1971 ). Diagnosis of nutritional disorders. While leaf and soil analysis have long been used as tools for

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M. Lenny Wells

.05. In conclusion, many southeastern U.S. pecan producers could likely reduce input costs by applying only those nutrients required according to the results of annual leaf and soil analysis. The results presented here suggest that the greatest potential

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Ockert P.J. Stander, Graham H. Barry, and Paul J.R. Cronjé

, W.W. Embleton, T.W. 1969 Development and current status of citrus leaf analysis as a guide to fertilization in California Proc. Intl. Soc. Citricult. 3 1669 1671 Jorgensen, K.R. Price, G.H. 1978 The citrus leaf and soil analysis system in Queensland

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Russell Galanti, Alyssa Cho, Amjad Ahmad, and Theodore Radovich

. Suddleson, M. 2008 Eutrophication and harmful algal blooms: A scientific consensus Harmful Algae 8 1 3 13 Hirae, H. 1976 Leaf and soil analysis in macadamia. Hawaii Macadamia Producers’ Assoc. 16th Annu. Proc. p. 65 Huett, D.O. Gogel, B.J. Meyers, M