Evaluation of Low Heat Unit Corn Hybrids Compared to Barley for Grazing

Research Coordinator: Dr. Akim Omokanye

Collaborator: Dr. Bart Lardner, Western Beef Development Centre (WBDC), Humboldt, Saskatchewan

Trial Site: Fairview Research Farm, MD of Fairview

From: Peace Country Beef & Forage Association 2014 Annual Report


Using corn to extend winter grazing in the Peace Country (PC) region of Alberta is gaining popularity. Corn is a good option for producers looking to extend the grazing season and reduce feed costs per cow per day. Well managed corn production and grazing plans will reduce or eliminate labour, feed and manure handling costs during the winter. One of the initial concerns was getting corn hybrids with corn heat units (CHUs) requirements that will match the CHUs of the PC region and elsewhere in Alberta and parts of Saskatchewan. Advances in plant breeding have resulted in hybrid corn hybrids that require less CHUs and therefore can be grown (for grazing or silage) more successfully in these areas. In 2012, PCBFA in collaboration with WBDC started a trial on the evaluation of low CHUs corn hybrids compared to barley for grazing in Fairview and area for 3 years (2012- 2014). The main objective was to evaluate 3 different corn hybrids (1 Monsanto; 1 Pioneer; 1 Hyland) and 1 forage barley (AC Ranger) for quality and yield grown at different sites in the Parkland area of Western Canada.


Methods

The trial was carried out at Fairview Research Farm, MD of Fairview (NW5-82-3W6) on RR #35. Prior to seeding, the site was harrowed and then sprayed with Credit® for pre-seed weed control. Soil analysis that was done for 0-6” soil depth by Exova laboratory, Edmonton, showed an OM of 7.1% and a pH of 5.8.


We seeded 3 corn hybrids (Monsanto corn DKC 26-25, Pioneer corn P7443R & Hyland corn 2D093) and AC Ranger barley variety. The CHUs for P7443R, 2D093 and DKC 26-25 are respectively 2100, 2350 and 2125. AC Ranger is a 6-row feed barley and has smooth awns. The crops were arranged in a randomized complete block design with four replications. Small plots measuring 1.4 m x 8.5 m were used. Corn and barley were both seeded and fertilized on May 30, 2014 with a plot drill. Seeding rates were 30,000 seeds/acre for corn hybrids and 100 lbs/acre for AC Ranger barley seed. All plots received equivalent amounts of fertilizer, based on the soil tests recommendations (corn - 93 lbs actual N/acre + 21 lbs actual P/acre + 22 lbs actual K/acre & barley - 67 lbs actual N/acre + 14 lbs actual P/acre + 16 lbs actual K/acre). Soil temperature at seeding was 9 degrees Celsius. In crop spraying of Roundup® at 0.67 L/ac application rate at the 4-5-leaf stage was carried for corn hybrids. For barley, 2-4 D amine® at 0.67L/acre at the 4-leaf stage was used. Hand weeding of volunteer canola took place twice in the corn plots.


On July 29, 2014, barley plots were harvested at the soft dough stage, weighed to obtain wet yield, sub-sampled and subsequently dried for dry matter (DM) yield estimation. On September 25, 2014, each corn hybrid was harvested for estimation of wet and dry forage yields. Five random corn plants were selected from each corn hybrid plot and then chopped with a small wood chipper for determination of feed quality in a commercial laboratory (Central Testing Laboratory, Winnipeg). On the sampling day, the numbers of cobs per plant and cob maturity were assessed.


Results

Forage Dry Matter (DM) Yield

Pioneer corn P7443R had significantly higher forage DM yield (4.36 ton/acre) than other corn hybrids and AC Ranger barley. The forage DM was similar for both Hyland 2D093 and Monsanto DKC 26-25. AC Ranger barley had 0.53 to 1.79 ton DM/acre less forage yield than the three corn hybrids tested. The DM obtained for the three corn hybrids is a reflection of their respective CHUs requirements. Pioneer P7443R with the least CHU produced the highest corn forage DM.


Forage Quality

The forage protein (crude protein, CP) was generally higher for barley (16.7% CP) than corn hybrids (7.32- 10.1% CP). The CP obtained for barley was adequate for both growing and finishing calves, and for a dry gestating cow in the mid and late pregnancy stages. For corn hybrids, the protein requirement of a cow in mid pregnancy was sufficiently met by the 3 corn hybrids. Both P7443R and DKC 26-25 corn hybrids had adequate protein for a cow in late pregnancy.


The forage energy (total digestible nutrients, TDN) of corn hybrids and barley was well above the energy requirements of a mature beef cow (55-65% TDN). Likewise, the energy requirements of growing and finishing calves (65-70% TDN) have been met by all corn hybrids and barley.


Barley had higher macro-mineral contents (Ca, P, Mg, K and S) than corn hybrids. The requirements of Ca, P, Mg and K by a dry gestating cow have all been met by barley and corn hybrids. But only barley had sufficient S content needed by a dry gestating cow.

The results (particularly on forage yield) show that early maturing silage type corn hybrids (e.g. P7443R) can provide substantial forage material for late fall and winter grazing. The role for grazing corn can be a flexible late fall or winter crop to balance off with existing winter graze options. It is important to control animal access to the crop with electric fencing. This will improve utilization of the crop while reducing trampling and wastage. In years of heavy snowfall, cattle may have better access to standing corn in comparison to swathed crops under the snow. With multiple inputs of seed, herbicide, fertilizer and fencing it is important to maximize the full potential of silage corn varieties to extend the winter grazing period. Intensive grazing of grazing corn can also provide adequate returns for producers. The key to successfully maximize profits is to manage costs effectively.

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