Journal of the NACAA
ISSN 2158-9429
Volume 10, Issue 1 - June, 2017

Editor: Lee Stivers

Can Forage Producers Gain More from Oat Harvest Management by Targeting Greater Dry Matter?

Han, K., Forage Agronomist, LSU Agcenter, School of Plant, Environmental, and Soil Sciences
Smith, D., Research Assistant, LSU Agcenter, School of Plant, Environmental, and Soil Sciences
Harrison, S., Small Grain Breeder, LSU Agcenter, School of Plant, Environmental, and Soil Sciences
Alison, W., Forage Agronomist/Extension Specialist, LSU Agcenter, Macon Ridge Research Station
Twidwell, E., Forage Extension Specialist, LSU Agcenter, School of Plant, Environmental, and Soil Sciences

ABSTRACT

Cultivation of oats (Avena sativa) for forage can be a feasible approach in the lower southeastern regions of the USA where perennial cool-season pasture is not dependable for winter feeding. A field demonstration with six oat varieties having different growth habits was conducted in a randomized block design to compare dry matter (DM) yield and feed value changes at several stages of maturity. Oat varieties demonstrated visually unique characteristics such as uprightness, leafiness, winter hardiness, and leaf blade width. Oats that were more upright, leafy, and winter hardy tended to produce more DM than their counterparts. The DM yield of oat varieites was greatest at the dough stage and least at the boot stage. The crude protein (CP) yield per acre of all oat varieties was greater at the heading stage than the dough stage because of higher CP concentrations in heading vs. dough stage of growth, which negated the higher DM yield in dough vs. heading stage of growth. This field trial demonstrated the importance of both variety selection and harvest maturity when utilizing oats for hay or as a cover crop.             


INTRODUCTION

Small grains such as oats (Avena sativa) and wheat (Triticum aestivum) have been valuable cash crops to produce grain throughout the USA. Due to utilization demands as a cover crop and forage, options have become more versatile. Small grains have the potential to produce high feed value forage at vegetative stage of maturity. In contrast to grazing, harvest for silage and hay is suggested at more mature stages such as late boot or early heading for the purpose of producing more DM with a minor degree of feed value sacrifice (Smith et al., 2009). Cow-calf operations in the lower southeast regions requires high feed value forage for actively growing heifers and steers during the winter/spring season. Cattle operations in the regions commonly overseed winter annuals into bermudagrass (Cynodon dactylon (L) Pers.) pasture to produce winter forage. Feed value of winter annuals are usually superior to warm season grass hay or dormant warm-season grass pasture.  

Annual ryegrass (Lolium multiflorum Lam.) is the major winter annual species grown in Louisiana for winter forage. However, prolific annual ryegrass growth can be a problem on warm-season grass hay fields during the spring transition period. Cultivation of oats on dormant warm-season grass pasture during the winter season could be a feasible approach to producing high feed value forage while generating less weed competition to the warm-season grasses. Oats can produce around 7,658 lbs per acre of dry forage through a three cut system in Louisiana and mature several weeks earlier than annual ryegrass (Alison et al., 2009). The CP and TDN (total digestible nutrient) in oat pasture averaged around 20 and 71%, respectively. However, CP and TDN in oats hay utilized in the southeast region averaged 11 and 62%, respectively (Han et al., 2007). Researchers (Brundage, 1970; Cherney and Marten, 1981; Barnhart, 2011) reported a continuous decline of CP while a substantial increase in cell wall constituents in maturing oats. Because oats are not commonly grown for forage in the lower southern region, information on the forage production of oats is limited. Therefore, a field trial was conducted with oats harvested at different maturity stages to determine quantitative and qualitative aspects of the forage potential of this small grain species.

MATERIALS AND METHODS

Location and Field Management

A field trial was conducted at the Louisiana State University AgCenter’s Ben Hur Research Station in Baton Rouge, LA (30°4’ N, 91°2’ W). Six oat varieties, including five commericial oat varieties and one genetic line variety, were chosen based on forage production potential. Oats were planted on November 4, 2014. Each oat variety included three subplots to be harvested at boot, heading, and dough stages of growth. Regrowth harvest was made only from boot stage harvested plots. Therefore, six oat varieties were harvested at the four development stages and the treatments were replicated four times. The oat seeding rate was 120 lbs per acre, and oats were planted on a prepared seedbed in 6- by 14-ft plots using a 7-row plot drill set at 7-inch row spacing. Each treatment plot alternated with a border plot of oats to reduce border effect. Soil type at the planting site was Cancienne silt loam. Soil pH was 6.16. Oats received pre-plant fertilization with 16-46-60-10 lbs /acre (N-P-K-S) of diammomium phosphate (DAP) and potassium sulfate fertilizer on November 12, 2014, then 90 lbs /acre N as urea ammonium nitrate (UAN) in mid-February.

Growth habit of oat varieties was visually evaluated based on relative scores on a scale from 1 to 10, with higher scores (10) corresponding with more upright, leafy, and winter hardy treatments. Leaf width was evaluated on a scale from 1 to 5, with higher scores (5) corresponding with wider leaves. This rating scale was used to quantify morphological differences among the oat varieites. Oats were harvested beginning on March 16, 2015 and ending on May 6, 2015 when variety reached growth stages of boot, heading, dough, and regrowth. 

Harvest, Sample Collection, and Feed Value Analysis

Harvests were made with a rotary cutter mower with a 30-inch cutting width and blades set 3 inches from the ground. An attached mulching bag was used to collect and weigh the herbage. A single center strip was collected from the entire length of each treatment plot. A grab sample of the herbage was taken from the mulching bag, placed into a paper bag, weighed, dried for three days at 55º C in a forced-air drying oven, then reweighed. Dried samples were ground in a Wiley mill (Thomas Scientiļ¬c, Swedesboro, NJ) to pass through a 1-mm sieve. Duplicate 0.50-g samples were used to determine in vitro true digestibility (IVTD) by the methods of Goering and Van Soest (1970). Neutral detergent fiber (NDF) and acid detergent fiber (ADF) concentrations were determined with an Ankom Model 200 fiber analyzer (Ankom Technology, Macedon, NY, USA) using a sodium sulphite procedure (Robertson and Van Soest, 1981). Crude protein (CP) was calculated as total N × 6.25 by rapid combustion using a LECO FP-528 Protein Analyzer (LECO Corp. St. Joseph, MI).  

Experimental Design and Statistical Analysis

Statistical analysis was conducted with Proc Glimmix of SAS version 9.2 software (SAS Institute, 2004). Oat variety and maturity at harvest, and the interaction between them, were considered fixed effects. Treatment differences were tested using pair-wise comparisons with Satterthwaite approximation for the denominator degrees of freedom as an option. Unless otherwise stated, all differences noted are at the 0.05 probability level.

 

RESULTS AND DISCUSSION

 

Growth Habit of Oat Variety and Impact of Oat Variety and Harvest Maturity on Performance

Monthly aerial temperatures during the 2014-2015 growing seasons were similar to the normal average temperatures. However, monthly rainfall of the site was lower than that of a normal year (Fig. 1).

Figure 1. Monthly precipitation and aerial temperature of Louisiana State University Agricultural Center Ben Hur Research Station in Baton Rouge, LA during 2014 – 2015 oat growing season, and normal year (30-year average).

 

Field observations found that oat varieties demonstrated unique growth habits as shown in Table 1. For example, Horizon 270 and LA99016 demonstrated less erect, less leafiness, more sensitive winter stress, and narrower leaf blades than FL0720-R6 and Horizon306. 

 

Table 1. Summary of growth habit (uprightness, leafiness, winter hardiness, and leaf width) of oat varieties.

The growth habit parameters seem to be closely related in the oat variety. FL0720-R6 and Horizon 306 received high scores for all the growth habit parameters. Based on growth habits, utilization of oat variety can be differentiated. Rate of water loss from harvested forage declines when canopy is heavy, juvenile, and leafy due to reduced air circulation within windrow (McDonald and Clark, 1987). Some oat varieties may be more advantageous for field drying because of lighter windrow formation potential than others. The DM yield, fiber content (ADF & NDF), CP, and IVTD differed by oat variety, harvest maturity, and the interaction between them (Table 2). This indicates that some oat varieties’ responses for DM yield and their feed values to a certain harvest maturity differed from other oat treatments.

 

Table 2. Significance of effects on DM yield, nutrient value (NDF, neutral detergent fiber; ADF, acid detergent fiber; CP, crude protein), and in vitro true digestibility (IVTD).

 

Feed Value and Productivity of Oat Varieties

Comparison of feed value indicated significant differences among the varieties, and the degree of the difference became less as the harvest maturity advanced to dough stage (Table 3). The numerical content of NDF, ADF, and CP among oat varieites did not statistically differ at dough stage (P > 0.05). Overall ADF and NDF in oat treatments at boot stage doubled at dough stage. As harvest maturity advanced, NDF and ADF concentrations increased, while CP concentration and IVTD decreased (Table 3). 

 

Table 3. Nutrient content (NDF, neutral detergent fiber; ADF, acid detergent fiber; CP, crude protein as % DM) and in vitro true digestibility (IVTD, % DM) of oat variety (entry) by harvest maturity.

 

The inverse relationship between forage accumulation and CP content at harvest maturity indicated that heading stage harvest is the most balanced harvest maturity compromising forage yield and feeding value (Fig. 2a). Accumulation patterns of NDF and ADF varied among the oat varieties with the advanced maturity. Regrowth from boot harvest plots accumulated additional DM until later in the growing season, and CP and IVTD in regrowth were similar with those in dough stage. Actual economic gains from early boot stage harvest and regrowth harvest were not obvious in this study due to the relatively low feed value of regrowth and less sum of DM production from the two cut system than a single cut at dough stage. Pairwise comparison of CP content in the oat treatments varied within harvest maturity and pooled mean CP in oat treatments did not differ much compared with DM yield (Fig. 2b). 

 

 

Fig. 2. Mean DM yield and CP content of oats by harvest maturity (a) and by oat treatments (b).

 

In general, the dough stage harvest achieved the most DM yield among the varieties, however, Horizon 720-R6, Horizon 306, and Horizon 201 produced more DM at the heading stage than LA 99016 harvested at the dough stage (Fig. 3 a). In contrast to DM production, CP yield per acre indicated that the heading stage produced the most CP among the tested stages of maturity (Fig. 3b). In spite of higher DM yield of oat forages harvested at the dough or regrowth stages compared to the boot stage, significantly lower CP content at the dough or regrowth stages caused a similar CP yield per acre to that at the boot stage (Fig. 3b).

Fig. 3. Mean DM yield (a) and CP yield (b) of oats by harvest maturity.

 

Regrowth from boot stage oat harvest can be an indicator for a dual purpose utilization (early grazing/grain harvest) potential. As previously discussed feed value gains from regrowth, gains from additional DM production from regrowth need to be justified depending on production goals.

 

SUMMARY AND CONCLUSIONS

Oats can be an option for winter forage during the spring transition period. Dynamics of DM accumulation and feed value changes indicated harvest of oats targeting hay production needs to be done no later than heading stage. Dough-stage oats produced the most DM; however, the low protein and low digestibility indicate feed value is not high enough to justify dough stage harvest because feed value does not meet the nutrient requirements of most classes of beef cattle. The lack of feed value superiority among oat treatments revealed selection of an oat variety for hay production can be accomplished based on DM accumulation. Even though there was no extreme weather events during this trial, potential variation in growing environment may warrant multi-year or multi-location trials.

 
LITERATURE CITED

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