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Container nurseries broadcast apply granular formulations of herbicides over-the-top of container crops and then apply irrigation. Depending upon spacing and plant architecture, up to 80% of the applied herbicide may land on the surfaces surrounding containers where it is then available to move offsite in irrigation runoff water. This study measured the amounts of isoxaben and trifluralin (from Snapshot 2.5TG) lost from a container nursery site during an irrigation event and monitored the dissipation of each in containment pond water. A 1.22 hectare container nursery production area was treated with Snapshot TG at 112 kg product/hectare and 1.27 cm irrigation was applied. Water samples were collected from the runoff water before it entered into the collection pond at the following time intervals: 0.25, 0.5, 1.5, 2.5, and 3.5 hours after runoff began. Water samples were also collected in the containment pond before treatment, after treatment, and then 1-3, 5, 7, 14, 29, and 60 days after treatment. Nearly 17% of the applied isoxaben was lost in the runoff water immediately following application. Isoxaben concentrations in the containment pond water decreased from a high of approximately 30 ppb immediately following the first runoff event to below lppb 60 days after application. No trifluralin was detected in the runoff or catch pond water.

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Abstract

Controlled-environment agriculture gives the greenhouse manager freedom to take advantage of opportunities which are unavailable in open-field agriculture. To take full advantage of this flexibility, a greenhouse manager must be prepared to be responsive to current crop production and market conditions. In this study, the problem of managing greenhouse crops for either maximum production or profit of operation is examined, particularly the question of when to terminate a given crop and to plant new seedlings. The effects on production of dividing the greenhouse to permit crops at different stages of maturity to be grown simultaneously are considered. The annual price fluctuation and its effect on crop scheduling decisions is discussed. A formal mathematical model for crop production is not needed in order to formulate an objective decision making method, rather one may make use of current and past production data to make crop management decisions. A decision-making guideline (an algorithm) based on some simple observations from the definition of a maximum is presented and used throughout as a guide for management.

Open Access

Acidification of < 1% of the effective root zone of a mature pecan tree (Carya illinoensis (Wanghenh.) C. Koch) significantly increased uptake of Zn into the tree and maintained elevated Zn in leaves for 9 years. Sulfuric acid and ZnSO4, applied in a shallow trench, lowered soil pH to a depth of 60 cm and increased volubility of Zn in the acid band. Large concentrations of CaSO4 were formed. Laboratory tests confirmed the movement and volubility of Zn in soils under conditions similar to those in the field. Tree roots did not grow into the acidified band, presumably due to high salinity, but proliferated extensively at the interface of the acidified band and calcareous soil.

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