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Fluid Journal : Summer 2014
15 The Fluid Journal Summer 2014 Summary: Proper water management approaches include using smaller amounts of nutrients directly to the crop as foliar treatments, bypassing soil applications. Using fluid fertilizers allows nutrients to be immediately available to the plant. The new era in water and nutrient efficiencies will be pushed to levels once thought impossible by using effective data collection and sound analysis techniques. Alittle reflection first. We were honored when asked to give our perspective on this subject, and it caused one of us to think back to the days of his grandfather and how he was taught to grow plants. In the 1950s everything was grown using 10-10-10 fertilizer, probably because of price rather than using precise fertilizer management. Irrigation was never mentioned because there was none in the area, namely the Eastern Shore of the Delmarva Peninsula. In Maryland, it was believed that 3 to 4 inches of rain that fell each month was sufficient to grow a crop. Our forebears were good farmers, possessing the wisdom of the day. As they shared their years of knowledge, we now have been asked to share our years of knowledge. Our hope is our experiences will help motivate others to take current knowledge of managing water and fertilizer use efficiencies in growing plants to new heights tomorrow. Times change So let’s start with the big difference between our forebears way of doing things and ours today. They were mostly self-taught via trial and error. Fate led us to a totally different path. After World War II, the electronic age was just starting and it was during this time that many ideas were developed and patented. One such patent was for the design of the capacitance probe. Summer 2014 • Vol. 22, No. 3, Issue #85 David Lankford and Frank Lichtner, Ph.D . Using effective data collection and sound analysis techniques is critical. The dilemma was that at that time the only form of electronics available was vacuum tube technology. The size and power needed to operate the tubes prohibited any deployment of instruments to an agricultural field and so it remained a concept rather than a practical solution. By the 1960s the USA was involved in the Vietnam conflict. During this time the military began advanced electronics at a time when tubes, transistors, and chips were all being used, sometimes in combination in one machine. Much was learned from the deployment of electronics and analysis of data collected. Little did we know that this would affect the future of those involved in agriculture! Enter probes Almost 30 years ago the concept of using capacitance probes to measure soil water content evolved as the new world of miniaturized electronics grew. By developing this technology in Australia, Peter Buss of Sentex Technologies drove ways to benefit growers who were struggling with limited water availability. He achieved many advances in robust probe design, reliable performance, and analytical software. But like so many inventions, the use of technology was initially limited to the purpose the inventor perceived: a tool for water balance studies and water management. It is now helping growers all over the world to manage water and nutrients. Budgeting When we were introduced to this technology, one of our first questions was how were the budget lines determined (Figure 1)? The explanation given to us was based on the principle that the soil texture determines the limits of how much water the soil can hold and how much water is available for the plant. Most of us in agriculture with knowledge of soils and agronomy have heard the terms “field capacity,” “wilt point,” and “ saturation. ” We were instructed to set the upper limit of the water balance as close to the field capacity of the soil as possible. It was pointed out that after a large water influx into the soil (rainfall or irrigation), the timeline graph would rise dramatically and then would decline quickly until the soil tension counteracted the drainage, and this point on the graph equaled “field capacity” (Figure 2). Field capacity was considered the situation where the maximum amount of water was available for the plant and is the best upper set point for water management purposes. The process to set the lower budget line was a little more contentious. There have been some who say just set the budget line at any percent of available water, and it will be OK. Others thought it should be set as a defined percent of available water