Considerations for spreading manure during warm weather: When spreading manure during the summer, it is important to consider the impact of high temperatures on nitrogen (N) loss from manure. Volatilization of ammonia during and shortly after application is greatly increased when temperatures are high. Several other factors including manure composition, time to incorporation, wind, soil pH and moisture, and application method will impact ammonia loss as well. Losing ammonia from manure is a direct loss of its fertilizer value and should be considered when planning application timing and calculating manure’s contribution to crop N requirements. Spreading manure when temperatures are above 25°C can result in a loss of 50% of the ammonia N within three hours of application.

It is acceptable to apply manure on established grasses, fields being seeded within two weeks of application, and berry fields IF: Expected precipitation and manure applications will NOT create nutrient or pathogen runoff to surface water (by overland flow or through tile drains)* T-Sum value in your area is greater than 200, Soil temperature is greater than 5oC, and Crop is actively growing (for established crops only)

“in general, manure application on any crops is not advised.” With the T-sum value hovering near 200 in several areas across the Fraser Valley, it is important to remember the other factors to consider before a forage field is suitable for spreading manure.

Refer to Manure Spreading Advisory #3 of 2017 (Nov 1, 2017) for the current Advisory: “in general, manure application on any crops is not advised.” The following Update does not change the Advisory. The T-Sum is one factor used to determine appropriate timing for the first manure application on grass fields. More importantly, however, decisions about the first manure application should consider the overall risks of runoff from the field, not just the state of the grasses. On some but not all fields, conditions will be suitable for manure application before T-Sum reaches 200. On other fields, conditions will not be suitable even after T-Sum reaches 200 (e.g. if fields are still saturated from rains). T-Sum values, a sum of daily mean temperatures above 0°C, for the region are listed below and compared with values for the same time last year and the historical average.