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In a perfect world there would be enough rainfall to supply agricultural crops with all the water they need in a growing season. This isn’t a perfect world though and farmers throughout the United States and around the world rely on irrigation systems to deliver water to crops. To meet the needs of growing populations they are working hard managing their operating systems to increase the efficiency of inputs, reduce waste, and maximize yields in a concerted effort to increase their net returns while conserving natural resources. Managing irrigation systems to foster efficiency and sustainability has become an important aspect of their businesses. Precision irrigation has become an invaluable tool in their arsenal, helping farmers to schedule and implement an irrigation strategy that encourages healthy root development, reduces nutrient, chemical, and water waste, while maximizing the utilization of water across every zone of every field.

Precision irrigation is changing how many farmers water their crops, turning irrigation into high tech systems. Efficient irrigation comes down to a key factor: applying only the amount of water plants needs, and ensuring they have it when they need it. Irrigation scheduling, in simple terms, is determining the “when” and “how much”.

The key factors in managing irrigation scheduling are:

  • Looking at how much water gets into the soil from rainfall
  • How much water the soil can hold overall, and
  • How much water the plant is using

Looking at these factors paints a picture explaining when and how much to water so crops don’t experience water stress and can efficiently utilize water available in the root zone.

Agriculture is changing, at what sometimes seems to be a rapid pace and more tools are becoming available for farmers to improve cropping systems management. A growing demand for increased food production, on less acreage and with fewer resources means the agricultural industry in general is constantly looking at ways to benefit production.

In irrigated cropland systems, irrigation scheduling and precision irrigation are becoming commonplace and provide many benefits:

  • Applying water to fields before plants experience water stress leads to yield maximization down the road
  • Efficiently scheduling irrigation so it’s only done when needed reduces water and labor costs
  • Fertilizer costs are reduced due to a minimization of runoff and leaching through to groundwater because water isn’t over applied and allowed to move out of the root zone
  • Water logging problems are minimized, helping to reduce soil salinity concerns in affected regions

Most importantly though, all of the benefits of precision irrigation are coming together to increase the net returns of farms.

When looking at irrigation scheduling for increased water use efficiency and plant growth, there are different approaches, varying in their methods and cost:

  • Checkbook method (Pro: easiest, Con: doesn't account for environmental factors)
  • Soil moisture sensors / probes (Pro: real-time data to make irrigation decisions, Con: some investment)
  • Modeling software (Pro: more complicated, Con: lots of data to consider)

The simplest route is to use basic calculators to roughly determine when to schedule irrigation. A common calculator used by farmers is the checkbook method1. This is a manual soil water balance accounting method taking into account available moisture levels and the amount of water a crop needs during each week of its life-cycle. The soil in the field is like a bank checking account; the checkbook method considers rain and irrigation as deposits to the account and crop water use as withdrawals from the soil water. Irrigation is scheduled to keep the checkbook balance in a range just below field holding capacity to prevent water stress, without over watering and causing leaching or runoff. It does not account for other environmental factors but simply uses mathematics to determine crop irrigation needs.

A slightly more technical method used for precision irrigation and scheduling involves using sensors to measure field conditions. They provide real-time readings of the amount of water available in the soil and the amount being lost to evapotranspiration through the plants.  Watching sensor measurements gives producers the ability to turn on water when plant and soil moisture levels drop below a certain threshold, and then shut it off when the desired level is obtained. Over application of water is significantly reduced reducing waste, input costs, and potential environmental impacts by only applying water when needed. Plant sensors take into account the water balance method; they measure water loss through evapotranspiration, showing crop use and then balance incoming and outgoing water levels to maintain adequate soil moisture for the plant. Soil moisture sensors assume that the soil moisture content largely determines the moisture status of the plant. If there is low soil moisture, the plant must work harder to take up that water, causing the plant stress. When soil moisture levels drop below a recommended threshold, irrigation is scheduled to prevent stress and yield reductions.

The most technologically advanced – and expensive – method of irrigation scheduling uses modeling software, and is a growing trend in cropping systems. Sophisticated tools combine soil and plant sensors, weather data, soil characteristics, historical trends, aerial and satellite imagery, and complicated computer algorithms to advise farmers when to water, and how much water volume to apply. Cloud computing brings the data directly to the farmer allowing access to it through a web or mobile platform. Farmers can control all aspects of their irrigation systems from turning pumps on and off, monitoring weather stations, viewing real time soil moisture levels from their smart phone or tablet allowing them to quickly assess irrigation needs and react accordingly.

Irrigation is a vital aspect of crop production for many farmers, without it their cropping systems would struggle to thrive and produce little harvestable commodities. It is though an expensive part of farming and producers are constantly looking for ways to reduce their inputs costs, increase the efficiency of their cropping systems, while maximizing yields and net returns. To better manage irrigation systems, many implement irrigation scheduling and precision irrigation to ensure water is applied when the plants need it most to reduce plant water stress and to reduce the problems that arise from overwatering. There are many options for irrigation scheduling ranging from simple calculators to intricate modeling software, providing farmers with choices to best fit their farming systems. Smart irrigation: yet another advance helping farmers to foster sustainable, efficient agriculture systems.

 

1 Irrigation scheduling checkbook method

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