When James Adkins started working at the Warrington Farm just south of Milton, Delaware, in 1999, the farm was plagued with poor drainage, noxious weeds and poor soil fertility. Now, 17 years later, steady improvements to the soil and the drainage system allow University of Delaware researchers the ability to study irrigation and fertigation treatments for plots of soybean, wheat and corn and to make recommendations to regional growers on how to best irrigate and fertilize their crops. Those issues are exceptionally important to farmers — in both Delaware, which boasts around 128,000 acres of irrigated cropland, and around the world — who must balance use of the correct amount of water and fertilizer to produce the best crop yields from the soils they are working. Given to the University by Everett Warrington in 1992, the Warrington Farm is equipped with a variable rate center pivot irrigation system, which was upgraded in 2012 from a previous version that Adkins, associate scientist for irrigation engineering at UD’s Carvel Research and Education Center, built with Ian McCann, an irrigation and water management specialist, in 2001. “At the time, it was like VHS and Betamax, and I built a Betamax,” said Adkins, who explained that before getting the new system in place, researchers would have to stand on the pivot point and wait for the water to hit a flag and then turn a combination of toggle switches to make the machine do what it needed to do. In 2016, the irrigation system was upgraded to reflect the latest advancements in irrigation management and technology. Now, researchers are able to use geographic information system (GIS) software to map where and how they want certain research plots irrigated. The primary goal is to evaluate and identify the most effective and efficient water management strategies to enhance crop production and nutrient management. To plant the crops, Adkins uses a tractor equipped with real-time kinematic steering that can be set up to drive plus or minus an inch one way or the other for each pass so that all the rows on the farm are planted perfectly straight. He then takes that map out of the tractor and uses it with the pivot to determine how the farm plots get irrigated. “We’ve got the farm randomized into about 300 individual 60- by 60-foot squares and we categorize the soils based on a range of factors such as electrical connectivity, which is a proxy for soil moisture holding capacity, and clay content. We’re categorizing them in such a way that we’ve got five tiers and we plant each of our treatments in each tier. We want to make sure that ‘Treatment One’ doesn’t always end up in the best soil and make sure it gets into all five tiers,” said Adkins. Each square is irrigated differently, and every morning the researchers collect data from sensors that monitor soil moisture content at 6, 12 and 18 inches. The data comes from watermark sensors that are hardwired to a wireless transmitter that sends data to a tower where 11 machines record all the information. The researchers look at soil moisture values daily and can see how soil moisture values change throughout the day. “We’ve got about 200 stations with three sensors each that log each hour so we’re looking at a large volume of data each day. We can tell where the roots of a crop are by looking at the soil moisture values because when the sun comes up, the plant starts using water so we’ll see that soil moisture profile start to drop. When the sun goes down, the plant is no longer using water so it will level off. By watching each depth, we can get a good idea where our root zone is and thus change how we irrigate,” said Adkins. By analyzing the data for each plot, the researchers can prepare a prescription for how the machine will run for the day. “If we have a treatment triggered by a sensor that reads 20 centibars or above – for instance, if we get in one morning and we have one plot at 21 centibars – that square gets irrigated,” said Adkins. “It’s a mechanism to be able to evaluate whether sensor-driven irrigation has an effect on yield and water use efficiency.” Trevor Aldred, who is working on the farm for the summer before heading to medical school after graduating from UD with an honors degree in biological sciences, enters the data every morning into a spreadsheet that is color coded to tell the researchers which plots need to be irrigated and how they need to be irrigated. With the soybean research, Adkins said the study is mostly devoted to the timing of application. “We find that soybeans respond to water at a very particular time and if you just water based on conventional methods, you’ll actually hurt yield because it will result in a plant that is too big and that falls down,” said Adkins. With the corn, they are looking at fertigation, mostly in regards to nitrogen use efficiency, with 11 different treatments replicated five times for a total of 55 treatment blocks.