Page 279 - Nutrient Management Planning Guide

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Chapter 8.2

To eliminate the need for winter application, producers may have to increase their manure storage capacity. Adequate storage is required to contain the manure produced during the winter months and allow for application at more appropriate times. This may require the construction of larger and more costly manure holding facilities than presently used by some producers. Alternatively, a small group of producers may work together to construct and share a larger storage facility. This approach reduces the costs associated for individual farms while providing the benefit of an increase in storage capacity.

Apply Manure to Meet Crop Nutrient Requirements

Crops require approximately three to seven times the amount of N than they do P. As a result, applications of manure, which may have a 2:1 or even a 1:1 ratio of N to P can result in the over-application of P. The over applying of P above crop need results in the build-up in the soil. Applying fertilizer and manure at rates that meet crop nutrient requirements will reduce the risk of nutrient build-up in the soil. By reducing the concentration of nutrients on or near the soil surface, the amount of nutrients available for transport in runoff water will be reduced.

A significant implication to applying manure based on P requirements is the affect on land requirements and transportation costs. Since crops use significantly less P than N, a larger land base maybe required for manure application based on P requirements compared to N requirements. Operators may need to purchase more land, rent additional land or build partnerships with surrounding landholders to secure the land-base required for a P-based manure application program. An expanded land base may also result in increased transportation costs if manure has to be hauled greater

distances. Other manure management strategies such as composting or generating bio-fuels may offer alternatives to transportation.

A NMP may be adopted that calculates manure application rates based on multi-year crop P demands matching P uptake to crop removal in a rotation over three to five years. Operations may need to improve their MMP and feeding strategies to either reduce the opportunity of N loss from the manure or increase the amount of P retained in the animal to maintain a higher N to P ratio. Manure with a higher N to P ratio provides a better nutrient balance for crops, making it easier to manage and reduces the risk of P accumulation.

Time Manure Application to Maximize Crop Uptake

Apply manure just prior to seeding or as close as possible to the time of active crop growth. Nutrients from the manure application can be used and taken up by the crop reducing the opportunity for loss from the system. The crop canopy will also provide protection from erosion and loss by rainfall and volatilization. Application on unfrozen surfaces increases the opportunity for the movement of dissolved nutrients into the soil through water infiltration. In addition, there is a greater opportunity for spring applied nutrients to be absorbed by the soil compared to late fall manure applications reducing the risk to surface runoff losses. Avoid application without incorporation of manure in the late fall as this increases the risk of nutrient loss during spring snowmelt.

The challenge to early season manure application is time, conflict with spring seeding and the risk of soil compaction if soils are wet. Custom applicators may be used to manage time constraints. Field and crop selection are important considerations when managing seeding and manure application. Select crops that will be seeded