Knowing Your Roots

Archive for April, 2015

Drip Irrigation: Doing More with Less

Blog 19

Most people are already familiar with drip irrigation—they’ve used soaker hoses in the garden or seen those thin tubes in greenhouses or even in orchards. However, on large-scale agricultural lands within Wisconsin, drip irrigation is rarely seen.  Since water is usually plentiful in the state, irrigation is delivered to crops with overhead sprinklers, traveling water guns or with rotating center pivot systems. This doesn’t happen in areas where water supplies are scarce.  In other grower regions – either in the U.S. or worldwide – growers use watering systems that can be controlled to only deliver the exact amount of water the plants need, via the system known as drip irrigation.

Drip irrigation was first used commercially in Israel in the mid-1900s when the advent of plastics made it possible. It continues to be a dominant form of irrigation in many arid (dry) regions where water is the most limiting factor in crop production. In the U.S., drip irrigation is found predominantly in dry agricultural regions, such as California and Florida, where hundreds of thousands of acres of high-value crops are produced using drip irrigation.  Historically, drip irrigation had been primarily used with permanent tree and vine plantings, but new research and applications have made it increasingly desirable for specialty crops, vegetables and even row crops like cotton and corn.

In Wisconsin, less than 1% of the 500,000 irrigated acres use drip irrigation (under surface drip, subsurface, trickle or other forms of micro irrigation) and much of this acreage is in small-scale vegetable production. Wisconsin growers may not face the level of water scarcity seen in the western part of the country, but as concerns over groundwater quality and quantity increase, it may be necessary to explore alternative production strategies.

Drip irrigation has been shown to allow for significant reductions in water and nutrients by better localizing applications in the crop root zone where they can be delivered only when needed by the plant. Also by creating a drier micro-climate in the plant canopy, the risks posed by plant diseases, which thrive in moist conditions, are also greatly reduced. Drip irrigation can provide additional advantages such as a precise delivery system for plant protectants without harming beneficial insects or the environment.  With these benefits, why don’t we see more drip irrigation used in Wisconsin?   Simple, the high costs of implementing this technology have limited its use, and it remains unclear if these benefits could justify its use in more humid climates with a drought-sensitive crop like potatoes.

Looking to the future where sustainable use of water resources in potato production has emerged as one of the industry’s highest priorities, Sarah Page, a UW-Madison Masters student in Agroecology and Horticulture under the direction of AJ Bussan, has conducted research trials at the Hancock Agricultural Research Station to address just those questions. She compared tuber yield, size and processing quality under standard center pivot irrigation practices and three rates of drip irrigation for commonly grown potato varieties. She found little effect of irrigation treatment and in most years and with most varieties, there were no differences in total yield or tuber size distribution. Surprisingly, the lowest water application rate for drip irrigation yielded slightly higher than the other two rates. This was likely due to increased nutrient leaching under the more heavily irrigated plots, which was supported by nitrate levels detected in plant tissues. A potential negative consequence of lowering irrigation amounts could be drought and heat stress on the tubers, which could have negative consequences for processing quality. However, when Sarah looked into this, she found little effect of irrigation treatment on reducing- sugar content – a contributing factor to undesirable dark colors when potatoes are fried.

Sarah’s research shows that it was possible to reduce water application rates by 25% without negatively affecting potato yield and quality attributes. That’s a lot! There are many steps that need to happen before drip irrigation could be economically feasible and sustainable on a large scale in the sands of Wisconsin, but it’s one more potential tool to add to the box.

For more information, contact Sarah Page at sapage@wisc.edu.

Environmental Modeling: Use, Implications and Public Trust in the Little Plover River Basin

New Family Farm water New Family Farm Map 2Have you seen the term ‘model’, ‘groundwater flow model’, ‘computational model’ or ‘environmental model’ when reading about water resources issues in Wisconsin, particularly in articles discussing the Central Sands region? Likely, the answer to this question is yes. Yet, you may wonder what modeling is and why it is important.  Questions occur, such as does modeling play a role in maintaining Wisconsin’s agricultural productivity? Will modeling aid long-range water resource planning? Are models trustworthy and do they have implications for short and long-term goals you have for your property?

Environmental modeling is a mathematical tool for investigating scientific questions involving complex environmental processes. Modeled processes may be related to geology, groundwater recharge and discharge, surface-water flow, groundwater pumping or other land use changes. Models mimic environmental processes at a time scale and spatial resolution that is defined by the user. By focusing on a key question (or set of questions), models can provide a way to assess, measure and predict what factors most readily affect a system as well as how and/or when a system is affected.  In Wisconsin, state agencies routinely develop and use environmental models for science-based decision support.

Recently, Dr. Ken Bradbury at the Wisconsin Geological and Natural History Survey; Dr. Mike Fienen at the U.S. Geological Survey, doctoral candidate Maribeth Kniffin at UW-Madison, and master’s candidate Jake Krause at UW-Madison have been collaborating to construct a groundwater flow model for the Little Plover River Basin and surrounding area in a study funded by the Wisconsin Department of Natural Resources. In parallel, Ms. Kniffin has been conducting a soil water balance model to estimate rates of groundwater recharge in different vegetation types, which were used in the groundwater flow model. The Little Plover River Basin was chosen for this pilot study because the river has been the focus of recent management concerns and because a great deal of hydrogeologic data already exists for this area. A working version and initial results of the groundwater flow and soil water balance models will be complete in June 2015.The Little Plover River groundwater flow and soil water balance models will enable researchers to test potential decision-making scenarios that affect regional agricultural productivity and sustainability of water resources. This will determine which types of land use and water management practices would be effective within the Little Plover River Basin.

Research has shown, however,  that in order to use environmental modeling for local decision-making purposes, the stakeholder participation in the development and evaluation of the model is just as, if not more, important as the model results. Stakeholder participation in model development and evaluation process provides the opportunity to raise questions about technical information used in the model, which can improve the model itself. Stakeholder participation can also create a greater public trust in model results and investment in potential decision-making options.

With this in mind, Dr. Bradbury, Dr. Fienen and Ms. Kniffin have been interacting with stakeholders during the development of the Little Plover River groundwater flow model. The stakeholders include a broad group that encompasses potato and vegetable growers, the village of Plover, local citizens, Trout Unlimited, the River Alliance and others to provide balanced inputs that represent all view-points. These interactions have greatly improved model inputs, such as irrigation pumping rates, land use and stream flows. Moving forward, Ms. Kniffin’s doctoral research will continue to engage stakeholders in a discussion about water resource management for the Little Plover Basin under different timescales ranging from very short (rainfall events, daily irrigation pumping) to very long (seasonality, climate change, landscape design). Through interviews and small group meetings, Ms. Kniffin will work with stakeholders to develop relevant performance criteria (i.e. minimum streamflows, agricultural productivity) and alternative management practices (i.e. pumping rate adjustments) for model testing. Ms. Kniffin will then conduct a series of model simulations to evaluate the ability of management practices to meet performance criteria and will present the results to the community. This project will help determine the spatial and temporal scope of future groundwater flow models necessary for decision-making in other areas of Central Wisconsin.

 

For more information about this project, see http://fyi.uwex.edu/littleplovermodel/ or contact Maribeth Kniffin at kniffin@wisc.edu. Ms Kniffin is the recipient of the prestigious Wisconsin Potato Industry Distinguished Graduate Fellowship for 2015-2016.

 

 

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