This publication presents and discusses concepts that are fundamental to understanding soil, water, and plant relationships and the soil water balance. Knowledge about soil water relationships can inform the decision-making process in agricultural operations or natural resource management, such as determining what crops to plant, when to plant them, and when various management practices should be scheduled. Understanding these concepts is useful for addressing both agronomic and policy issues related to agricultural water management.Zachary M. Easton, Assistant Professor and Extension Specialist, Biological Systems Engineering, Virginia Tech Emily Bock, Graduate Research Assistant, Biological Systems Engineering, Virginia Tech

Virginia usually receives ample rainfall to support agriculture, but droughts in 2002, 2007, and 2010 led to severe problems for farms in many regions. Using groundwater for irrigation can help manage drought risks on farms without access to ponds or streams. However, installing groundwater wells can be expensive and time-consuming. The amount of water obtained from wells can vary in different regions of the state. This bulletin is intended to provide agricultural producers with information on technical and regulatory issues related to irrigating with groundwater.

Pesticide sprays consist of at least 95% water. Water quality plays an important role in pesticide performance. The following issues may indicate a compatibility problem with pesticides and spray water quality: - Pesticide does not work at labeled rates; - Difficulty mixing sprays or clogging of nozzles; - Inconsistent pest control observed in fields or plots; - Pests seem resistant to a new pesticide active ingredient, or - Crops are lower quality or lower yielding. Understanding how water quality characteristics such as pH, water hardness, turbidity, and total suspended solids affect the adsorption and persistence (half-life, storage time) of a pesticide can help pesticide applicators reduce or eliminate compatibility issues and improve pesticide effectiveness

Mixing two or more pesticide products can allow for the treatment of several pests at the same time, improve pesticide performance, and ultimately saving time and money. However, physical and chemical tank mix incompatibilities can occur when combining two or more pesticides. Physical incompatibility is the failure of pesticide products to stay uniformly mixed and can result in layering, products settling out of solution, or clumping. A chemical incompatibility is the result of a chemical reaction between pesticide products. A chemical incompatibility is less visible and can be harder to detect. This publication focuses on basic factors that influence product compatibility (agitation speed and method, water temperature, mixing order, carrier type, and chemical formulations) and summarizes best mixing practices to address these factors.

Spray water problems may arise due to water quality and management decisions. Certain aspects of water quality can reduce the efficacy of the pesticide as well as affect how the pesticide interacts with the plant surface or targets pests. Evaluating and testing spray water chemistry can help identify water quality problems that might otherwise be overlooked. This publication will examine possible solutions to spray water problems, including the use of adjuvants and other additives to enhance pesticide performance.