MSU seeks better ways to use water, nutrients

One of the hallmarks of Michigan agriculture is its diversity and the contribution of specialty crops to the state’s economy.

Most Michiganders know their state is a national leader in production of blueberries, tart cherries and apples. But Michigan is also a leading grower of ornamental landscape plants. According a recent national assessment, the Michigan nursery and greenhouse industry ranked seventh in the country with an annual economic impact of more than $900 million.

As with other types of agriculture, landscape nurseries in Michigan are faced with many challenges. These include rising costs of production and increased concerns related to environmental impacts of intensive agriculture.

Managing irrigation and fertilization are two of the most critical elements in any nursery production system. Effectively and efficiently managing water and nutrients can have a direct effect on the economic and environmental impacts of production, two of the three often-cited “triple bottom lines” of sustainability.

For example, if growers under-irrigate, trees may undergo water stress; if growers over-irrigate, it may result in leaching of nitrates and phosphorus from the site. Likewise, overfertilization can lead to adverse environmental impacts, such as surface water or groundwater contamination, while inadequate nutrition can reduce crop yield and quality.

Trials offer clues

Over the past six years, we have conducted a series of research trials at Michigan State University to improve nutrient and water management of landscape conifers and shade trees. The overall goal of the program is to improve our understanding of the growth and physiological response of landscape shade trees and conifers to varying water and nutrient inputs. Support for these projects has been provided by MSU Project GREEEN, the Michigan Department of Agriculture and Rural Development Horticulture Fund, USDA Specialty Crop Block grant program and nursery industry partners.

An innovative aspect of our research approach is the use of an automated leachate collection system to determine the amount of water and nutrient leaching from a container nursery at the MSU Horticulture Teaching and Research Center near East Lansing. The leachate collection system collects leachate from an individual row of containers in the production area.

Leachate from each row is collected, and the total runoff is measured by a series of tipping-bucket rain gauges and an automated data logger. By comparing the amount of water reaching the tipping buckets to the amount of irrigation applied, we can determine the fraction of irrigation water that leached through the system. In addition, we collect samples of leachate for chemical analysis periodically during the growing season. By knowing the volume of water leached and the concentration of nitrate and phosphorus, we can determine the amount of nutrients lost.

To date, the research program has yielded several key outputs for growers including refining fertilization rates, proving information on nutrient diagnostic techniques, comparing conventional and organic fertilizer sources, and developing crop coefficients (ratio of water need to reference evapotranspiration) from conifers and shade trees in Michigan.

We are initiating a new phase of research for the system with the addition of a sensor-based irrigation system. This system will connect irrigation values to a series of moisture probes, enabling the trees to be watered automatically based on container substrate moisture levels. Using the leachate collection system will enable us to evaluate the effect of different target moisture levels on water leached, in addition to our standard measures of tree growth and quality.

As with our earlier trials, the ultimate goal of the project is to help growers achieve a win-win scenario where they can optimize tree growth and quality with reduced costs, while at the same time minimizing potential environmental impacts.

Cregg writes for the MSU departments of Horticulture and Forestry.

07123056B.tifON-SITE RESEARCH: MSU researchers are investigating the impacts of water and nutrient management in this container nursery at the MSU Horticulture Teaching and Research Center.

07123056C.tifTIP the BUCKET: Irrigation water that leaches from each row in this test nursery drains to a collection point, where it is measured using a tipping-bucket rain gauge.

07123056D.tifCRITICAL COMPONENTS: Managing irrigation and fertilization efficiently is critical to sustainable nursery production.

This article published in the July, 2012 edition of MICHIGAN FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.