Washington State University

WSU Dairy

January 2012
Volume 21, Number 1
Intercropped Biennial Canola for Silage
This work is a demonstration of concept that in year 1 canola can be intercropped with peas and the forage ensiled 70 days later, and a canola oilseed crop subsequently harvested in year 2. Justification for the work is that biodiesel production has increased demand for oilseeds such as canola. Oilseed crops have been used in rotation with wheat since the late 1970s (Painter et al., 2009) with winter canola having a higher yield potential than spring canola (Herdrich, 2001). Botanically, when winter canola is seeded in the spring or early summer, it will grow as a biennial crop, in that it will remain vegetative and produce prostrate shoots and an extensive root system in the first year, undergo shoot dieback during the winter, and resume vegetative and reproductive growth in year 2 (Kirkegaard et al., 2008). A dense plant population is not required for winter canola because the plants can get quite large after flowering (Young, 2009). This provides a possibility for intercropping with an annual crop that would not be in severe competition for space in the first year and would not be present in the second year. Intercropping with a legume may have the added advantage of supplying nitrogen to the canola crop, especially in its second year as the legume roots and residues decompose.

Thus, winter canola, when seeded in spring or early summer will grow as a biennial crop that allows for a forage crop to be harvested in year one. The aim of this experiment was to evaluate biennial canola as a dryland forage for silage production and to incorporate the silage into a total mixed ration (TMR) for lactating cattle. A mixture of peas (100 lb/acre) and canola (4.5 lb/acre) were planted in early July and 70-d later the standing forage was cut and ensiled into an air-tight plastic silo bag. The harvested forage contained 31% DM and yielded about 1 ton DM/acre. The ensiled canola/pea forage contained 13.3% CP, 29.8% NDF, 24.1% ADF, 38.6% NFC, 0.31% S, 6.92% lactic acid, 1.97% acetic acid, no detectable butyric acid, and a pH of 4.3. The nitrate-N concentration in the pre-ensiled forage (139 ppm nitrate-N) was reduced about 80% (28 ppm nitrate-N) in the ensilage as the nitrate presumably was converted to nitrous oxide and emitted. The estimated NEL value of the canola/pea silage was 0.71 Mcal NEL/lb, DM. A feeding study was done using 36 multiparous Holstein cows in which cows were group-fed either a control TMR or a TMR that contained 9% canola/pea silage (DM basis). In the TMR, the canola/pea silage replaced a portion of the alfalfa hay and corn silage such that CP and NDF percentages were similar between treatments. After 21-d the canola/pea silage was increased to 15% (DM basis) of the TMR. Neither daily milk yield nor milk composition were affected by the partial substitution of canola/pea silage for alfalfa hay and corn silage in the TMR. The intercrop of canola and peas yielded an ensilage that was palatable in a TMR and had good feeding value as indicated by the chemical composition, in vitro digestibility, and results of the feeding study with lactating cows. In year 2, the yield of canola oilseed was 2200 lb/acre.

Creating sustainable systems for agriculture in dryland regions should include economical options for producers to diversify. The intercropping of canola and peas yielded an ensilage that was palatable with an acceptable feeding value as indicated by the chemical composition, in vitro digestibility, and feeding study with lactating dairy cows. Ensiling the forage crop and feeding it as part of a TMR avoided potential problems that might occur with direct grazing. Thus, biennial forage canola appears to be a viable option in crop rotation systems in dryland areas to diversity crop production and obtain forage for ruminants.

This study was supported by the College of Agriculture, Human and Natural Resources at Washington State University and by a grant from the BioAg Program, WSU Center for Sustaining Agriculture and Natural Resources.
Ron Kincaid, Professor Emeritus
WSU Puyallup Interior Plantscaping, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA, 253-445-4524, Rita Hummel