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  • Author or Editor: John R. Young x
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Though high electrical conductivity (EC) levels are commonly held to be the primary limiting factor for using spent mushroom compost (SMC) as a growing substrate, EC can be reduced by leaching. This allowed SMC to be successfully used for growing plants. Leaching reduced EC of the substrate solution from as high of 30 dS·m-1 (mmhos·cm-1) to 2 to 3 dS·m-1, a level acceptable for growing plants. The initial EC and container capacity determined the number of leachings and total volume of water required to lower EC of SMC substrates to acceptable levels. As the concentration of SMC was increased, a higher number of leachings or larger volume of water were required to adequately reduce EC levels. In trials spanning 2.5 years, SMC was effectively used as a substrate in the production of marigold (Tagetes patula) `Yellow Girl'. Benefits to plant growth from SMC incorporation included a slow release of nutrients as the SMC decomposed and a good air-filled pore space/water-holding capacity when amended with a commercial nursery mix. From these trials, it is recommended that SMC be incorporated at rates of 25% to 50%. It is not recommended that SMC be used in concentrations over 50% because the EC may be too difficult to manage and the high levels of air-filled pore space of SMC. Though season may affect the initial EC level of SMC, such variation is minimized by leaching while differences in plant response are more likely to be attributed to environmental conditions. No differences in plant growth were observed among SMC sources.

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Pesticides were applied to ‘Rio Grande’ peach [Prunus persica (L.) Batsch] trees at recommended rates from bloom to harvest using three sprinkler configurations on a center pivot and an air-blast sprayer. Fruit scab infection rates with a patented sprinkler configuration (Piggy-back) that has spray nozzles mounted on a lower truss rod of the center pivot were equivalent on 12 and 23 June 1987 to those with the air-blast sprayer. Scab infection rates for standard impact-nozzles and for a deflector nozzle configuration were equivalent to each other, and tended to be lower than the infection rate for the unsprayed fruit, but higher than the rate for the air-blast sprayer or piggy-back configuration. Brown rot, bacterial spot, and insect catfacing (the other fruit defects observed at harvest) were independent of the method of pesticide application. It may be feasible to chemigate peach orchards with center-pivot irrigation systems.

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