BEST MANAGEMENT PRACTICES:
Guide for Producing Nursery Crops
Third Edition
2013

WATER & NUTRIENT MANAGEMENT PRACTICES

Introduction

The Federal Clean Water Act of 1972 requires that all sectors of agriculture develop effective procedures to prevent pollution of our nation’s water resources. Container nurseries, though considered non-point source polluters, are no exception. Nutrient management plans formulated for a container nursery must consider both water and nutrient applications, because container-grown plants require irrigation on a daily basis during the majority of the production cycle. Thus, nutrients can leach from containers before being used by plants. Watering too often or excessively during each irrigation event results in nutrient loss from the container via leaching.  Reapplication of fertilizer is often necessary to maintain desired plant growth rate, potentially increasing nutrient loading to the environment.

Due to necessity to irrigate and fertilize container-grown crops on a frequent basis, precise water and fertilizer application are the primary practice to minimize fertilizer runoff.

In the absence of specific state legislation providing guidance for developing a nutrient management plan, container nurseries are advised to implement the best management practices outlined in this manual.  Documentation that a nursery follows these practices will help provide strong evidence that the nursery is minimizing the amount of contaminants (nutrients, pesticides, and sediments) entering surface and groundwater. Furthermore, collecting date to document the effectiveness of these implemented BMPs could be valuable in exonerating a nursery if specific environmental problems are attributed to the nursery.

Overview of the Water and Nutrient Management

Planning Process

The factors that need to be considered when developing a nutrient management plan for a container nursery are given in Figure 43. Attention should focus on four main BMPs:

Applying fertilizers at recommended rates, according to species.
Monitoring of nutrient levels (electrical conductivity; EC) in containers.
Managing irrigation to reduce the amount of nutrients leached.
Collecting and recycling runoff from production areas, or reducing nutrient levels in runoff before it leaves the nursery property.

Factors to Consider


Site Evaluation

A site evaluation involves examination of geographical factors including the topography, surface conditions that contribute to water movement, and those factors that mitigate the effects of surface water runoff. Provisions for collection structures and vegetative filters should be considered. Consider these geographic factors before developing new nursery sites (see section on Nursery Site Selection).

 

Collection Structures

When collection structures are used, the goal is to capture the runoff and recycle or treat the water before it is released from the property. Additional provisions should be made for stormwater runoff, if the collection structures are also used for this purpose. Determine the storm event magnitude you would like to manage (25, 50, 100 year storm, etc.) and consult with a qualified engineer and the Soil Conservation Service to design management structures.

Runoff collection structures are an effective means to capture and reuse/treat water leaving the production area.

Several factors should be considered when developing a nutrient management plan for a container nursery.

Vegetative Zones

Grass or tree and wetland vegetative buffer zones are an alternative to collection structures for producers not capturing and recycling water. Vegetative zones facilitate reduction of sediment, pesticide, and nutrient loads leaving the property in runoff. Containment structures installed before the vegetative zones slow the flow of water and trap soil or substrate particles extending the life and efficacy of the vegetative zones. Some nutrient reduction of nitrogen (by denitrification) and phosphorus (by adsorption) may also occur in the containment structure (see section on Runoff Water Management).


Runoff collection structures are an effective means to capture and reuse/treat water leaving the production area.

Containment structures installed before the vegetative zones slow the flow of water and

trap soil or substrate particles extending the life and efficacy of the vegetative zones.

Irrigation Management

The overriding objective is to design and operate an irrigation system that will supply adequate and uniform application of water to the plants with minimal nutrient leaching from containers and minimal runoff from the production area.

 

Plant Water Requirements

Plants are grouped according to water requirement (Table 2) (e.g. species, container size, and plant age) to maximize water use efficiency (see section on Irrigation Application Amount).

 

Minimal distances are maintained between overhead-irrigated containers without sacrificing plant quality (see section on Overhead Irrigation System Design).

 

Irrigation Systems

Existing irrigation system is checked bi-annually to determine if the system is delivering water uniformly (see sections on Overhead and Microirrigation System Design).

 

Irrigation is applied only when needed for just long enough to uniformly wet the container substrate with minimal leaching (see section on Irrigation Application Amount).

 

Cyclic irrigation is used to reduce leaching and runoff (see section on Methods of Application).

A well designed and adequately maintained irrigation system is essential to minimize water use, and as a result will also minimize the amount o fertilizer leaving the production area. Plants grouped according to water requirement will maximize water use efficiency.

Substrates

Substrate Selection and Management

Select container substrates that are best adapted to the plants species and management (see section on Container Substrates). Avoid substrates that are too porous and require frequent watering (see section on Container Substrate Physical Properties). Methodology for determining substrate physical properties is given in Appendix B.

 

Plant Nutrient Requirements

Fertilizer Type and Rate

The general principle is to apply the least amount of fertilizer to maximize plant growth, but in a way that minimizes nutrient leaching. This can be accomplished with different management strategies using dry granular fertilizer or solution fertilizer applied at various rates, depending on the intensity of management (see sections on Pre- and Post Plant Fertilizer Applications and Controlled-Release Fertilizer).

 

Plant Nutrient Requirements and Application

Fertilizer applications should be made at recommended rates based upon plant requirement (species), container size, plant age, growth rate, and the time of year (see sections on Pre- and Post Plant Fertilizer Applications and Controlled-Release Fertilizer).

 

Fertilizer applied through the overhead irrigation system should be properly managed, so it does not greatly increase the chance of significant nutrient runoff from the nursery (see section on Fertilizer in Irrigation Water).

 

Monitoring Substrate Nutrients

Nutrient levels in container substrates should be monitored to assure levels are appropriate for desired growth. This should be performed on representative plants of similar size and with similar fertilizer and irrigation programs (see section on Monitoring Container Substrate Nutrient Status).

 

Fertigation application rates and reapplication of granular fertilizer should be based on monitoring the electrical conductivity (EC) of substrate solution. EC should be checked at least monthly during plant production (see section on Monitoring Container Substrate Nutrient Status).

 

Record of Fertilizer Application

An accurate record should be made of fertilizers applied for each plant type (high, medium or low nutrient requirement) and container size. This data should be recorded in such a way that total nitrogen and phosphorus applied for the nursery could be calculated on an area basis or on a crop basis (see section on Record of Fertilizer Application). Another approach would be to keep fertilizer receipts to calculate per acre application amounts of N and P for the nursery. See Appendix C for examples. Fertilizers can be applied through the irrigation system or directly on the substrate surface (granular or controlled-release. Fertilizer type, plant species, container size, and time of year are factors affecting fertilizer application amount.

Regardless of application method, the goal of a fertilizer program should be to apply the least amount of fertilizer to maximize plant growth in a manner that minimizes nutrients exiting containers and leaving the production area.
The container substrate EC should be regularly monitored (at least monthly) to determine the substrate solution fertilizer levels.

Developing a Water and Nutrient Management Plan

The management strategies outlined above provide the components of a Water and Nutrient Management Plan. Implementation and documentation of these suggested nutrient and irrigation management practices such as fertilization records, monitoring EC of substrates, and determining irrigation application uniformities demonstrates that you are applying water and nutrients in an environmentally conscious way. A checklist (Table 10) is given to help evaluate your practices and identify risks.

Developing a Water and Nutrient Management Plan documents fertilizer and water use as well as the methods of fertilizer and water application. Such information will help you evaluate your management practices, identify cost-efficiencies and reduce risk.

Table 10. A checklist of practices used to develop a nutrient management plan.


Conducted site evaluation?

Yes

No

Runoff water from production area is contained or directed through vegetative filters?

Yes

No

Plants are grouped according to water need?

Yes

No

Minimal distance is maintained between overhead irrigated containers?

Yes

No

Irrigation system has adequate uniformity?

Yes

No

Irrigate only when needed with minimal leaching?

Yes

No

Use cyclic irrigation to reduce leaching?

Yes

No

Substrate has acceptable water-holding capacity?

Yes

No

Fertilizer applied according to crop need and recommended rates?

Yes

No

Electrical conductivity of container substrate is recorded at least monthly?

Yes

No

Amount and type of fertilizer recorded for each container size and plant type?

Yes

No