Corn Intercrops to Improve Forage Protein Content for Beef Cattle

Trial Site: Fairview Research Farm

Research Program Manager: Dr Akim Omokanye

From: Peace Country Beef & Forage Association 2018 Annual Report

Corn forage can fit well in the grazing system, as it meets the nutritive composition requirements for many categories of cattle, particularly those of beef cows in mid-and late-stage pregnancy. Corn forage protein levels would not normally be adequate for beef cattle diet at all physiological stages. Corn forage CP and fibre content may decrease from silking to milk–dough stage. In addressing the shortfall in corn forage CP for both young and mature beef cattle, producers may add some form of CP supplement or good legume hay. Corn intercropping with legumes or other annual crops is an option to consider for improving forage corn CP content at minimal cost. Intercropping allows efficient use of resources, which allows a reduction of production costs and offers greater total forage yield, as well as improved forage nutritive value. The objective of this study was to compare corn intercropped with annual legumes and non-legume crops to corn monocrop in terms of forage yield and quality. This report provides a summary of a 2-year trial (2017 and 2018).

Methods

The trial site was at the Fairview Research Farm in 2017 and 2018.

A randomized complete block design with four replicates was used each year. The following eight treatments were investigated:

CM: Hybrid Pioneer 3944 corn (2000 corn heat units, CHUs). This was seeded as a monocrop (Check)

C-FP: Corn intercropped with CDC Horizon forage pea

C-CC: Corn intercropped with crimson clover

C-HV: Corn intercropped with hairy vetch

C-FB: Corn intercropped with Tabasco fababean

C-SB: Corn intercropped with soybean variety TH 33003, with 2400 CHUs

C-TR: Corn intercropped with tillage radish

C-ACM: Corn intercropped with the following annual crop mixture:

The C-ACM seeding rates were 19.2 lbs/acre barley (variety: CDC Maverick), 3.20 lbs/acre peas, 1.60 lbs/acre hairy vetch, 0.40 lb/acre crimson clover, 0.40 lb/acre Winfred forage brassica, 0.40 lb/acre green spirit Italian ryegrass, and 0.40 lb/acre sunflower.

The same Hybrid Pioneer 3944 corn was used for treatments 2 to 7 above.

Seeding was done with a plot drill equipped with disc type openers on May 25, 2017 and on May 28, 2018. The corn in all treatments was seeded at 27 inch row spacing, to achieve final stands of about 32,000 plants/ acre. Between rows of corn, we seeded two rows of companion crops, which were 9 inches apart. Both corn and the companion crops were seeded simultaneously. The companion crops in the corn-intercropping treatments were seeded at 40% of their respective recommended monocrop seeding rates.

Small plots measuring 1.15 m wide and 8 m long were used. We only applied 50% of the recommended fertilizer rates, based on soil tests done before seeding. The fertilizer blend was only applied to the rows with corn each year. The companion crops/annual crop mixtures were not fertilized. The legumes were inoculated at seeding with appropriate rhizobia inoculants. Pre-emergent weeds were controlled with glyphosate herbicide at 0.67 L/acre. Except for the corn-annual crop mixture and the corn-tillage radish intercrops, postemergence (in crop) weed control was with Basagran® Forte herbicide at 710 mL/acre when the corn was at 5-6 leaf stage. The corn-annual crop mixture and corn-tillage radish intercrops were hand weeded the same day the other plots were sprayed.

Two corn rows and two rows of each companion crop were hand-harvested per plot and weighed on September 15, 2017 and on September 24, 2018. Corn was harvested at kernel half milk line stage in 2017 and at kernel blister stage in 2018. All harvested materials were shredded using a wood chipper.

Two 1-kg fresh composite forage sub-samples per treatment - one for replications 1 & 3, and the other for replications 2 & 4 were shipped out for quality analysis to A&L Canada Laboratories Inc., London, Ontario.

Results

Intercropping corn with other annual crop species significantly affected corn plant height, corn forage DM yield, and total forage DM yield (Table 1). Significant differences also existed among the companion crop DM yields and the botanical forage contribution of companion crops towards total production (yield).

The CM had the highest plant height (230 cm), while C-TR had the lowest corn height (160 cm).

The corn forage DM yield was significantly higher for CM than all of the intercrops (Table 1). Out of the intercrops investigated, C-SB produced significantly higher corn forage DM yield than the other intercrops (except for C-CC). Both C-TR and C-ACM had significantly lower corn forage DM yields than CM. The C-ACM produced significantly higher companion crop forage DM yield than the other companion crops. Overall, except for CTR, total forage DM yields were not decreased by the additional seeding of other crops with corn, but the figures were rather maintained or slightly increased when compared with CM.

The companion crop forage DM yield from C-ACM constituted 65% of the total forage DM yield in the C-ACM intercrop, which was the highest, followed by that of C-TR, which constituted 54%. In comparison, other companion crops only made up 20-37% of the total forage production (DM yield).

The forage CP was significantly influenced by intercrops. Both C-HV and C-ACM had significantly higher forage CP content than the other intercrops, as well as CM (Table 2). The C-ACM and C-HV respectively had 40 and 44% increases in forage CP over CM.

A mature beef cow requires 7-11% CP, while 12-14% CP is needed by growing and finishing beef calves. All corn intercrops tested had adequate CP for a mature beef cow, but only corn-hairy vetch and corn-annual crop mixture intercrops met the CP requirements of young and mature beef cattle. This shows that for backgrounding and finishing calves, corn-hairy vetch and corn-annual crop mixture intercrops are a potential protein alternative (protein-rich diet) to the low protein corn monocrop.

For the forage macro minerals measured, only Na and S were affected significantly by intercropping (Table 2), with C-TR showing significantly higher Na and S (except for C-ACM) than the other intercrops and CM.

Energy is also one of the important criteria for forage quality evaluation, particularly in beef cattle production in cold climates. The forage energy determined here by total digestible nutrients (TDN) was significantly influenced by intercropping (Table 2). The C-SB had higher TDN than C-FB, but had similar levels to other intercrops and CM. All intercrops and CM produced higher TDN yield than C-TR.

Although the corn-soybean intercrop had the highest forage TDN, all treatments tested had adequate TDN for mature beef cattle, which require 55-65% TDN from mid-pregnancy to during lactation. Also, the treatments tested were well within the 65-70% TDN recommended for growing and finishing calves. Intercropping with soybeans produced a 2.5% increase in forage TDN over corn monocrop. This improvement in energy is crucial for winter range forage and could be translated into less supplements and reduction in feeding costs.

Conclusion

Corn-annual crop mixture and corn-hairy vetch intercrops seemed to have potential to improve total forage DM yield and CP content (no supplementation necessary for young and mature beef cattle). Both Corn-hairy vetch and corn-annual crop mixture intercrops were the only ones that had sufficiently met the protein requirements of young and mature beef cattle. All intercrops, as well as corn monocrop, had sufficient TDN for young and mature beef cattle. For improved corn forage protein for beef cattle, corn-hairy vetch and corn-annual crop mixture intercrops would be recommended.