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Craig D. Stanley and Gurpal Toor

that is used sets the potential for subsequent water and nutrient use efficiency. Although all irrigation system methods differ in degree of efficiency of application ( Smajstrla et al., 2002a ), improper design or operation of any system can further

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Xin Zhao, Qianqian Dong, Shubang Ni, Xiyong He, Hai Yue, Liang Tao, Yanli Nie, Caixian Tang, Fusuo Zhang and Jianbo Shen

crop management in the orchard with root/rhizosphere-based nutrient management. Enhancing nutrient-use efficiency through optimizing fertilizer input, improving fertilizer formulation, and maximizing biological interaction effects helps develop healthy

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Martin P.N. Gent

area, biomass distribution, and fruit production. This acclimation should be observable in terms of changes over time in the radiation, water, and nutrient use efficiencies. The present work examines water and nutrient uptake of greenhouse tomato crops

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Michelle Hadawi-Broeske and Helen C. Harrison

Renewed interest in soil conservation over the past decade has led to greater research efforts in the area of living mulch cropping systems. However, crop/mulch competition continues to present challenges. The objective of this study was to determine what effect two types of chemical growth suppressants (Mycogen 6121—an herbicidal soap, and Royal Slo-grow—a soil plant growth regulator) had on the water-use efficiency, nutrient use, and soil-shading ability of two annual living mulches, ryegrass (Lolium multiflorum) and crimson clover (Trifolium incarnatum). Two greenhouse experiments were performed in sand culture using a modified Hoagland's soap, one rate of growth regulator, and a mechanical treatment of mowing. Significant differences in nutrient use and soil-shading ability were obtained. The second experiment (69 days) replicated the ryegrass treatments less one rate of soap and included the legume crimson clover with one rate of soap and one rate of growth regulator. Results from both experiments will be discussed.

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Mary Ann Rose

Timing nutrient application to periods of high nutrient demand could increase nutrient use efficiency and reduce the potential for fertilizer leaching or runoff. However, current recommendations for field nursery and landscape ornamentals (extension publications) suggest fertilizing in late fall and early spring despite research with perennial fruit crops that demonstrates low uptake potential during those times. Research is needed to resolve this apparent conflict. Application rates for woody ornamentals, established in the 1960s and 1970s, also need reexamination in the light of environmental concerns.

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Carolyn F. Scagel, Guihong Bi, Leslie H. Fuchigami and Richard P. Regan

, and N has been shown to influence the photosynthetic capacity and nutrient use efficiency of Rhododendron ( Karlsson, 1994b ). The lack of interaction between N04 rate and urea treatment suggests that spraying plants with urea must alter other

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Charles A. Sanchez

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Masud A. Khan and James N. McCrimmon

The multiple use of water from aquaculture to supplement irrigated crop production could minimize the cost of growing fish and irrigating crops. Aquaculture effluent was utilized to supplement the fertility and irrigation of six native shrub species (big sage, fourwing saltbush, mountain mahogany, Mormon tea, rubber rabbitbrush, and winterfat). Plants were established in two container types: 20-liter standard polypot and nonwoven UV-stabilized Duon synthetic fiber growbags. The plants were irrigated with fish effluent or city water. Plants irrigated with fish effluent were not given any fertilizer treatment, while plants irrigated with city water were fertilized with Osmocote®. Fish effluent was suitable for production of fourwing saltbush, rubber rabbitbrush, big sage, and winterfat. Fourwing saltbush irrigated with effluent had the best survival rate, while mountain mahogany irrigated with effluent had the poorest growth and survival rates. Big sage, rubber rabbitbrush, and winterfat had better growth and survival rates in the growbags, while Mormon tea had better growth and survival rate in the polypot containers.

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Patrick H. Brown

The aim of this research was to determine the seasonal patterns of N demand and uptake in mature almond trees and to use this information to develop an integrated computer model to guide fertilization management. To this end sequential whole tree excavations were conducted at 5 stages during a 15-month period. At each harvest date, five entire mature trees were excavated and partitioned into leaves, root, trunks, and branches. Samples were then analyzed for total nutrient content and differences in nutrient content between sequential harvests, which represents tree nutrient demand and tree nutrient uptake. Infromation on seasonal N uptake dynamics and total yearly N demand has now been integrated into a user-friendly interactive computer program that can be used to optimize N fertilizer management. The details of this program will be discussed. In summary, the determination of N fluxes in almond demonstrates that the majority of N uptake and demand occurs from late February through to early September and that the primary demand for N is for nut fill and nut development. N demands can therefore be predicted by estimating yield and can be applied during the periods of greatest N uptake from the soil which occurs during nut development. By timing N applications with periods of greatest demand, and matching N application rates with crop load we provide growers with a tool that will encourage maximum efficiency of use of N fertilizers. Maximum efficiency of use will result in a minimization of N loss from the orchard system.

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Mark Gaskell and Tim Hartz

Nutrient management practices must be tailored to the crop, environment, and production system if nutrient efficiency and environmental water quality protection are to be achieved. This requires consideration of fertilizer choice, placement, application rate, and timing. These factors have been characterized as the “4Rs” of nutrient stewardship—right material, right placement, right rate, and right timing. The factors affecting the choice of fertilizer material have been described previously for agronomic crops, and include plant nutritional requirements, soil conditions, fertilizer delivery issues, environmental risks, product price, and economic constraints. Although those factors are applicable to all crops, the unique features of intensive horticultural production systems affect their interactions. This article discusses fertilizer choice as it affects productivity, profitability, sustainability, and environmental impact of intensive horticultural crop production. Diverse fertilizer materials are available for specialized application to provide nitrogen, phosphorus, potassium, and other plant nutrients for different horticultural needs. These fertilizer sources can be formulated as dry or liquid blends, but increasingly higher solubility materials are used to target plant growth needs even in field operations. Composts can have useful applications—particularly for certified organic production—but their high cost, bulk, and relatively low efficiency limit their use. Profitability can be affected by fertilizer cost—typically a relative small percentage of overall costs in intensive production systems—and the improved efficiency of these specialized materials often improves profitability. There are also sustainability issues with the manufacture, transport, and efficient use of different fertilizer sources. Such factors as soil chemical reaction changes, effects on soil salinity, and loss of organic matter also can adversely affect sustainability, but systems are available to maintain soil quality while using more efficient fertilizer sources.