Collaborating Producer: Lawrence & Lori Andruchiw, Happy Valley
Research Coordinator: Dr. Akim Omokanye
Corn grazing for extending the grazing season in the Peace is gradually expanding, with PCBFA playing a major role in creating awareness on its potential and suitability in cow-calf operations. Corn hybrids with lower corn heat unit (CHU) requirements, which are suitable for silage and grazing, are now available from a variety of sources including Pioneer Hybrids, Pickseed/Champion Feeds and BrettYoung. Corn has a high total input cost, which could be slightly below or above $200/acre depending on the fertility status of the site and seeding rate. Corn has a high fertility requirement, but fertilizer costs may be lower if manure is used. At RedStar farms in Fairview, a late fall soil tests in 2010 following corn grazing for 3 out of 4 years on the site showed sufficient amounts of N, K and S for subsequent corn crop. Then, we estimated a savings of at least $30/acre in fertilizer cost for the site. Here, in this report, the effects of manure application and inorganic fertilizer on corn growth, forage yield and feed value will be examined.
Methods
Site: The trial took place at Double LA Farms in Happy Valley (RGD Road 75, SW-05-78–07-W6), near Spirit River, Saddle Hills County. A total of 27 acres was seeded to 4 different corn hybrids, but for this trial we used about 3.0 acres of the site. The corn hybrids planted consisted of Pickseed 2501RR, Pickseed 2219RR, Pioneer P7213R, and Pioneer 39F44. We had 2 fertility sources, which were made up of:
1. Commercial fertilizer blend (85 lb actual N/ac + 42.5 lb actual P/ac) - fertilizer rate following soil tests.
2. Manure plus 1 /2 commercial fertilizer blend from 1 above. Here in this report, both 1 and 2 above will respectively be referred to as CF and M+CF.
Prior to any fertility treatments on the site, the site was worked and lightly harrowed. The commercial fertilizer was then broadcast and the manure spread. Then the site was re-harrowed. Following manure tests in a commercial laboratory (EXOVA), the manure application calculation indicated that the manure had 10.02 lb N/ton. We spread a total of 18.8 t/acre with a Hydra-spread (hydraulic push-gate manure spreader).
The corn hybrids were planted on May 20, 2012 in a randomized block design on 27 acres of land at the rate of 30,000 kernels/acre with a 6-row corn planter at 30-inch row spacing and at a seeding depth of 1.5- 2 inches. Weeds were controlled once with Roundup at 0.67 L/ac.
On October 5, 2012, corn hybrid forage yield was determined from three 17.5ft long corn rows per treatment. The corn forage samples were weighed fresh, then we chopped some corn plants with a corn chopper for determination of moisture content and feed value in a laboratory. On the sampling day, the number of cobs per plant, moisture content and cob maturity were determined.
The total direct input cost of corn was calculated for both fertility sources.
Results and Discussion
Number of Cobs and Cob Development
The mean number of cobs per corn plant was similar for the 4 corn hybrids tested (1.00 to 1.30 cobs per plant) (Table 1). Also fertility type did not affect the mean of cobs per corn plant (1.13 vs 1.23 cobs per plant). At sampling for forage yield determination on October 5, 2012, of the 4 corn hybrids, 39F44 and P7213R were the most advanced in cob development/maturity, with most cobs in the two-third milk line stage. A few cobs from 39F44 and P7213R were in the early dough stage. The other 2 hybrids (2501RR and 2219RR) were in the half milk stage.
Dry Matter (DM) Yield
The mean forage DM of corn hybrids was significantly higher for 2219RR (except for 2501RR) than the other hybrids (P7213R & 39F44, Table 1). Over the 4 corn hybrids, the mean forage DM was similar for both fertility sources (Table 1). Corn hybrid 2219RR significantly benefited from M+CF application better than the other corn hybrids. The mean yield advantage from M+CF over CF in the first year (2012) was little (7.92%).
Corn Feed Value
The mean protein content was highest for P7213R (9.18% CP) and lowest for 39F44 (7.62% CP). The mean protein content appeared to be slightly favoured by M+CF application. Some form of protein supplementation (using either a protein block or a good legume hay) would be required during grazing because of the low protein contents from most corn hybrids (regardless of fertility sources), which were just enough to meet the requirements of dry cows in the mid pregnancy stage. The mean forage energy (TDN) contents were >62% for all corn hybrids. Fertility source did not seem to have had any impact on forage energy content (Table 2). Generally, the TDN contents obtained in this trial were enough for cows’ requirements before calving.
The mean forage Ca content was significantly higher for corn hybrid P7213R (0.41% Ca) than the other corn hybrids, which all had <0.30% Ca content (Table 3). The mean Ca content appeared to be slightly improved by M+CF than CF. Overall, corn hybrid P7213R appeared to have higher Ca content regardless of fertility sources. With CF application, P7213R had 0.44% Ca compared to <0.27% Ca for the other corn hybrids. But when M+CF was applied, P7213R had the highest Ca content (0.38% Ca), closely followed by 2501RR with 0.35% Ca, while the other corn hybrids had <0.27% Ca. Of the 4 corn hybrids, only P7213R had adequate Ca content to meet the requirement of 0.31% Ca for growing and finishing beef. However, for dry pregnant cows, all corn hybrids had sufficient Ca (>18% Ca) content that is required by these classes of cows.
The mean forage P content was similar for the 4 corn hybrids. M+CF appeared to have slightly favoured P content. With the exception of P7213R, all corn hybrids had higher P content with M+CF than with CF. None of the mean P contents for the corn hybrids had sufficient P content to meet the P requirements of any classes of beef cattle. For the resulting Ca:P, only 2501RR and P7213R had >2:1 mean Ca:P for the corn hybrids. On a general note with the inconsistencies obtained for Ca, P and the resulting Ca:P, which were outside the requirements of beef cattle, some form of feed blends or commercial minerals would be needed during grazing.
Input Costs for Corn
The total input cost for both CF and M+CF are shown in Table 4. Majority of the total input cost came from seed and fertility with both contributing over $200 to the total cost of growing corn for grazing at this site. M+CF incurred an extra cost of $24.23 for the manure application.
Corn Grazing
The site was grazed with 77 cows and 2 bulls. Grazing started on November 18 and ended Dec 22, giving a total of 99 cow days/ acre. The lower number of cow days obtained here was because of lower corn yield, which resulted from low moisture during the growing season. The producer ran a-2500 volt fence line, but had a problem with cows breaking through the fence. So he thinks the fence should have 4-5000 volt to keep cows in.
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