Thursday, March 28, 2013

Winter Small Grain Silage Fertility

Many farmers planted winter triticale, winter rye, or winter wheat last fall in order to take a spring harvest to make up for the low haylage yields in 2012. Applying enough nitrogen at green-up will be crucial to raising the yield potential from 2 to 4+ tons of DM per acre. Supplying enough spring nitrogen will also increase crude protein from about 14% to nearly 20% DM if the silage is harvested by the flag leaf stage (Feeks 9, Figure 1) The application rate of spring nitrogen needed for high yielding, high quality winter small grain silage may range from 0 to nearly 100 lb. per acre depending on the previous crop in the rotation, and the field manure history.

Figure 1: Growth Stages of Winter Small Grain Silages

Fertility Management at Planting
Typically rates of 10-20 lb. of nitrogen per acre are applied at planting for wheat that is grown for grain. Fall nitrogen rates for small grains grown for silage are currently being re-evaluated across NY with support from the New York Farm Viability Institute (grant summary). Too much fall nitrogen leads to excess fall growth, leaving the small grains more vulnerable to damage over the winter. If the small grain is greater than 6 inches tall going into the winter, the crop will likely be partially or completely damaged by snow mold. Placing enough phosphorus with the small grain seed at planting is also critical for winter survival and spring growth if the fields do not a have a history of manure. Work by Peter Johnson in Ontario has shown that mixing 100 lb/acre of MAP with the wheat seed had higher yields (92.5 bu/acre vs. 82.9 bu/acre) and better winter survival (85% vs. 35%) than wheat without phosphorous. 

Spring Fertility Management Depends on Field History
One of the most common planting situations for winter grain silage last fall was after corn silage. The amount of spring nitrogen needed will depend on the amount manure applied before planting the small grain. Winter grain silage fields with high manure rates (>5,000 ga/acre) may still respond to a small nitrogen application at green-up (20-30 lb/per acre). Fields where 3,000 to 5,000 ga/acre of manure was applied may respond to up to 50 lb/acre of nitrogen. If little or no manure was applied at planting than small grain silage yields and quality may respond up to 75-100 lb. of nitrogen per acre. Manure nitrogen content can vary greatly from farm to farm and should be taken into account before deciding how much nitrogen fertilizer should be applied to small grain silages in the spring. 

Small grain silage following a haylage field that contained over 50% alfalfa or clover and had at least 6 inches of growth will probably not require much spring nitrogen fertilizer. Lodging can occur from over fertilization of nitrogen without responses to yield or quality. In these situations farmers may still want to apply 20-30 lb. nitrogen per acre at green-up as the nitrogen from the previous legume will not start to mineralize and become available to the small grain until temperatures increase later in the spring. The nitrogen from manure and soil organic matter will also not start to become available until the temperatures rise. If fields were mostly grass and did not receive manure, then at least 75 lb. per acre of nitrogen should be applied.

Small grain silage planted after soybeans, field peas, or snap beans will likely to respond to a middle range of nitrogen rates (40-60 lb. per acre) as there will be some legume nitrogen that should be available to the small grain silage.

Small grain silage planted after a small grain will likely require between 75 & 100 lb. of nitrogen per acre. Yields of small grain silage following a small grain will likely be lower due to higher disease, insect, and weed pressure compared to the other scenarios described above.

Currently a state-wide effort in New York is underway to fine-tune these general recommendations for nitrogen application to small grain silages. This blog entry will be updated as appropriate. The Google Map for the Winter Small Grain Silage Nitrogen Study 2013 is now online at Photos will be uploaded from now until these trials are harvested in May 2013. Click on the individual markers for more information and photos from each on-farm location.

Spring Applications of Phosphorous, Potassium, and Sulfur
Small grain silages may also benefit from applications of other nutrients besides nitrogen in the spring. While fertilizer response rate trials studying phosphorous, potassium, and sulfur have not yet been conducted on small grain silages, results from previous research on winter triticale, rye, barley, and oats grown for grain will likely meet all the nutrient requirements of silage

Bottom Line
1. Managing nitrogen fertility can increase winter small grain silage yields from 2 to over 4 tons of DM/acre.

2. The amount of nitrogen fertilizer needed is very dependent on field history.

Phosphorus Response in Wheat Production
Peter Johnson, Ontario Ministry Agriculture and Food

Winter Forage Triticale
Tom Kilcer, Jerry Cherney, Karl Czymmek, Quirine Ketterings Cornell University
Cornell Agronomy Fact Sheet 56

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