Tone Ag Consulting Ltd.

Two people have called me disappointed with the way their corn crop yielded after manure application.  The issue seems to be that some parts of the fields got the nitrogen they needed, other parts were applied with manure that had a lower nitrogen value than average and that left the crop hungry for nitrogen.

How can we keep this from happening again?  Here are some suggestions.  Note that not all of these will work for every operation and some of them may add to the expense, so pick and choose the ones that work for you.

Applicator

• Make sure to agitate the manure storage very thoroughly to reduce variability in the nutrients in the manure.
• Make sure the entire field is covered at as even a rate as possible
• Record the gallons on a regular basis (40 acres or less would be ideal).  Manure applicators in Manitoba are required to record the gallons applied on a field basis, but the more precisely we know what gallons went on what areas, the better we can estimate nutrients
• Take at least 3 manure samples per application (roughly at 25% complete, 50% complete, and 75% complete) to give a better idea of what amounts of nutrients went on what parts of the field

Crop Scout

• Soil sample the field again prior to seeding to check soil nitrogen levels
• Take tissue tests in late spring / early summer so that supplemental nitrogen can be applied if needed
• Recommend additional synthetic nitrogen as needed

Manure Management Planner

• Recommend application rates based on barn averages rather than provincial averages
• Follow up on application with an updated estimate of the nutrients actually applied

Caveats

There are some things that must be kept in mind.

1. Ensure that nutrient application rates comply with the regulations.  Two key clauses to note here in Manitoba are:

12(1) No person shall apply livestock manure to land other than as fertilizer on land on which a crop (a)is growing; or (b)will be planted during the next growing season.

and

12(1.4) No person shall apply livestock manure to land in a manner or at a rate of application that, taking into account the crop that the person farming the land is fertilizing with the manure, may result in the concentration of residual nitrate nitrogen being

(a)more than 157.1 kg/ha (140 pounds per acre) within the top 0.6 m (2 feet) of soil at any place in the application area for soils (i)of soil class 1, (ii)of soil class 2, and (iii)of soil class 3, other than soil class 3M or 3MW;

(b)more than 101 kg/ha (90 pounds per acre) within the top 0.6 m (2 feet) of soil at any place in the application area for soil classes 3M, 3MW and 4; or

(c)more than 33.6 kg/ha (30 pounds per acre) within the top 0.6 m (2 feet) of soil at any place in the application area for soil class 5.

2. Applying manure to meet nitrogen needs means that there will be an excess of phosphorous.  Depending on the levels of phosphorous in the soil, these fields will have to be taken out of rotation for a number of years.
3. There will always be variability in the manure and field conditions.  No matter how precise the recommendations and testing, some areas of the field need more nitrogen than others and some areas of the field will get more nitrogen than others due to factors such as the tractors turning around, overlapping passes, variability in the manure, and so on.  For more on this, explore Precision agriculture.
4. All the normal agricultural best practices need to be followed – e.g. the perfect nutrients don’t help much if the seed has a 5% germination rate and what comes up is eaten by corn borers.

Looking Ahead

I’ve spoken with people who are working on an infrared sensor that allows applicators to analyze manure nutrients accurately in real time.  This would allow applicators to adjust the rate of manure application in to ensure an even and precise distribution of nutrients across a field.  For example, you could set your rate at 130 lbs. nitrogen/acre and have the sensor tell you to speed up or slow down to meet that requirement.  This would be a huge improvement over the current method which works from estimates and averages from previous years.  If you are interested in this, they are doing field testing this fall and I would be happy to pass on their contact information.  This is a development I’m watching closely as having a higher level of precision would be hugely useful.