Abstract
Randomized factorial combinations of fertilizer and irrigation treatments (rate and/or source) are essential to test best management practices (BMP) for vegetables grown with plasticulture. This requires fertilization and irrigation to be applied independently from one another. In the past few years, five types of drip-irrigation systems have been used in different experiments. Their selection and design are presented here, as well as their respective advantages and disadvantages. In Type I systems, single drip tapes of different flow rates are used to create simultaneously water and fertilizer rates, thereby confounding the effects of irrigation and fertilization. When irrigation or fertilization treatments involve sources, treatments need to be delivered independently to each plot. In this case, a Type II system includes several injectors connected to separate main lines. When treatments are rates only, a set of valves and water meters at each plot are used to apply treatments based on operating time (Type III). This type is simple, but requires an operator to close the valves at predetermined times. Type IV and V systems involve the use of multiple main lines and different apparent flow rates for each treatment. Different apparent flow rates may be created with drip tapes of different nominal flow rates or with multiple drip tapes bundled together. A single injector (Type V) may be used for small numbers of treatments ( 10), but larger tests require the use of multiple injectors (Type IV). In all cases, changes in pressure and flow rate need to be monitored throughout operation. Because of their relatively low labor requirement for operation, Type I (with confounding of water and fertilizer effects) and to a lesser extend Type V (without confounding) are best suited for onfarm demonstrations.
