End of Project ReportQuality evaluation of oats relies primarily on hectolitre weight and, while it is an
important characteristic, work carried out at Oak Park and elsewhere has shown
that it does not accurately measure grain quality. Consequently, the selection of
oat lots and varieties which have a high milling value has been limited, as present
techniques fail to accurately determine the characteristics most closely related to
milling quality. In this regard the kernel content and the ease of husk removal,
termed the hullability, are the most important. This study has developed a new
test for assessing oat kernel content, which is more rapid and cheaper than
techniques currently available. Despite its obvious importance, oat hullability has
not been assessed to date in quality evaluation due to the absence of a test
procedure. However, this obstacle has now been overcome. The results of this
work also provide a much better understanding of how hullability of individual
varieties can be assessed, as well as investigating how this could be manipulated
at field level. Using the methods developed, the selection of varieties with
enhanced processing characteristics can now be carried out more precisely for
Irish conditions. The field trials conducted to evaluate the effect of agronomic
practices on quality indicated that the effect of factors such as nitrogen rate and
seed rate was small in comparison to variety, which had the largest and most
consistent effect. The variation in quality could not be completely explained by
variation in the panicle characteristics studied. Increasing the nitrogen rate
increased yield with the optimum being 160 kg N/ha in 1998 and 1999. However,
lodging became a very significant factor at nitrogen rates above 100 kg N/ha in
1998, although it did not occur in 1999. This work supports the current Teagasc
nitrogen recommendations for oats where levels of 110-140 kg N/ha (Soil Index
1) are advised

Browne, R.

Burke, James I.

White, E.M.

T-Stór

FACTORS AFFECTING YIELD ANDQUALITY OF OATSAuthorsJ.I. Burke1, R.A. Browne1,2and E.M. White21Crops Research CentreOak Park, Carlow2 Queen's University,Department of Applied Plant Science,Plant Testing Station,Crossnacreevy,Belfast BT6 9SHISBN  1 84170 207 2May 2001____________________________________________CONTENTSSUMMARY ......................................................................................1INTRODUCTION............................................................................1METHODS AND RESULTS ..................................................................... 2The assessment of milling quality ................................................................. 2Hectolitre weight ............................................................................................ 2Kernel content................................................................................................. 3Hullability ....................................................................................................... 4Effect of agronomic factors ............................................................................ 5Yield and Lodging........................................................................................... 6Kernel content................................................................................................. 6Hullability....................................................................................................... 7Hectolitre weight and screenings ................................................................... 7Panicle conformation and implications for quality ..................................8Characteristics of an ideal variety ................................................................. 9CONCLUSIONS ........................................................................................... 10REFERENCES .............................................................................................. 111SUMMARYQuality evaluation of oats relies primarily on hectolitre weight and, while it is animportant characteristic, work carried out at Oak Park and elsewhere has shownthat it does not accurately measure grain quality.  Consequently, the selection ofoat lots and varieties which have a high milling value has been limited, as presenttechniques fail to accurately determine the characteristics most closely related tomilling quality.  In this regard the kernel content and the ease of husk removal,termed the hullability, are the most important.  This study has developed a newtest for assessing oat kernel content, which is more rapid and cheaper thantechniques currently available.  Despite its obvious importance, oat hullability hasnot been assessed to date in quality evaluation due to the absence of a testprocedure.  However, this obstacle has now been overcome.  The results of thiswork also provide a much better understanding of how hullability of individualvarieties can be assessed, as well as investigating how this could be manipulatedat field level.  Using the methods developed, the selection of varieties withenhanced processing characteristics can now be carried out more precisely forIrish conditions.  The field trials conducted to evaluate the effect of agronomicpractices on quality indicated that the effect of factors such as nitrogen rate andseed rate was small in comparison to variety, which had the largest and mostconsistent effect.  The variation in quality could not be completely explained byvariation in the panicle characteristics studied.  Increasing the nitrogen rateincreased yield with the optimum being 160 kg N/ha in 1998 and 1999.  However,lodging became a very significant factor at nitrogen rates above 100 kg N/ha in1998, although it did not occur in 1999.  This work supports the current Teagascnitrogen recommendations for oats where levels of 110-140 kg N/ha (Soil Index1) are advised.INTRODUCTIONIn Ireland, oat crops are grown mainly for the horse feed and milling markets.Both require well-filled grains that are sound and free from contamination,although the particular requirements vary between both markets.  For the horsefeed sector, grain must have a minimum hectolitre weight of 52 kg/hl and be freefrom diseases with good colour.  For the milling market, oats should have a highhectolitre weight, high kernel content, good hullability and low screenings, as wellas minimum kernel blackening and breakage.  In order to meet these requirements,2it is essential for modern varieties to have, in addition to suitable qualitycharacteristics, a high yield and stiff straw, as well as good resistance to diseases,particularly mildew, crown rust and oat mosaic virus.Recent work at Oak Park has focused on exploiting the potential of oats as a breakcrop in integrated crop production systems, as well as elucidating the factorsinvolved in the production of high yielding and enhanced quality oat crops.  Thislatter work was conducted in a collaborative research programme with QueensUniversity Belfast at the Department of Applied Plant Science, Plant TestingStation, Crossnacreevy.METHODS AND RESULTSThe assessment of milling qualityHectolitre weightCurrent quality evaluation relies mainly on measuring the hectolitre weight of thegrain.  Hectolitre weight is a measure of the density or specific weight and isthought to be an indicator of grain quality, particularly potential extract yield.However, it is not a direct measure of a processing characteristic and has beenshown by Meyer and Zwingelberg (1981) to be unsuitable for the prediction ofextract yield.  McGarel and White (1996) reported that hectolitre weight onlyaccounted for 19% of the variation in kernel content across a range of varieties.  Inthis research, a relationship was found between hectolitre weight and millingquality, particularly kernel content, within each variety but a poor relationship wasfound between the two when comparing between varieties Fig.1.  For any givenhectolitre weight variety A had a higher kernel content to that of variety Billustrating the failure of hectolitre weight to accurately measure milling quality.The failure to assess characteristics directly related to value for milling, such askernel content and the ease of husk removal, termed the hullability, is related tothe absence of rapid and reliable tests.  The poor relationship between quality andhectolitre weight between varieties presents particular difficulties in the selectionand recommendation of oat varieties, where hectolitre weight is one of the mainselection criteria as it does not necessarily mean the variety will have good millingquality.  The milling industry is interested in methods for better defining andassessing quality purchasing criteria to better quantify the impact the purchasedoats will have on mill efficiency.3Fig. 1: Relationship between hectolitre weight and kernel contentThe first priority of this research was to develop and assess methods to moreaccurately determine milling quality.  A laboratory dehuller (Streckel andSchrader KG, Model BT459/e) was utilised to mimic the dehulling stage of themilling process.  With this, a protocol was developed to provide a rapid method bywhich kernel content and hullability could be assessed.  Test milling was carriedout over a range of varieties.  The kernel contents obtained from the dehuller werecompared with the current standard method of hand determination, and thehullability, which could not previously be assessed, was compared to millersobservations of particular varieties.Kernel contentKernel content is the characteristic most closely related to the millers extractyield of product.  The current hand method of kernel content determination is tootime-consuming and expensive to perform on commercial samples.  There was ahigh positive correlation between the hand and dehuller methods of kernel contentdetermination (r2=0.90) (Fig. 2) and, therefore, confirmed the suitability of thedehuller for use as an alternative method of kernel content determination.However, the dehuller kernel contents were consistently about 1 to 2% lower thanthose determined by hand, due to abrasion of the kernel that occurred in thedehuller.  There were significant differences between varieties in kernel content.Barra had the highest, while Aberglen, Aintree and Gerald were among the lowest.717273747576777850 52 54 56 58Hectolitre weight (kg/hl)  Variety A  Variety  B4Fig. 2: Comparison of hand and dehuller methods of kernel contentdeterminationHullabilityHullability, or the ease of husk removal, has important implications for millefficiency.  A variety with poor hullability will require greater impact speedswithin the dehuller during milling and result in greater kernel breakage, therebydepressing the millers extract yield.  In extreme cases, varieties, such as Mirabel,may even be unmillable because the husk is so difficult to remove.  Hullabilitywas assessed as the percentage of grain remaining unhulled after test milling.  Ahigh percentage of grain remaining unhulled indicates that the husk was difficultto remove and, therefore, has poor hullability.  The percentage of grain remainingunhulled, of a range of varieties, after test milling using the protocol developed, ispresented in Fig. 3.  Barra has particularly good hullability, with a low percentageof grain remaining unhulled, Image was intermediate, while the varieties Gerald,ACNN and Kingfisher had poor hullability and, therefore, poorer milling quality.The methods developed provide a useful tool for the evaluation of quality, inparticular by breeders developing new varieties and in the evaluation of varieties707274767880 Hand Dehuller5within variety testing for Recommended List status.  It also offers the prospect ofmillers using these methods to improve quality evaluation.Fig. 3: Effect of variety on hullability assessed by test millingEffect of agronomic factorsAgronomic guidelines for the oat crop are well-established in terms of yield andlodging.  However, the effects of agronomic factors on quality are less clear due tothe absence of methods to assess the processing characteristics directly related tovalue for milling.  Field experiments were conducted at Oak Park to investigatethe effect of agronomic factors on quality, using both the novel methodsdeveloped and conventional methods of quality evaluation.Factorial field experiments were conducted in 1998 and 1999, investigating theeffect of five nitrogen rates: 70, 100, 130, 160 and 190 kg/ha, two seed rates 200and 300 seeds/m2, on two commercially important varieties, Aberglen and Barra.The nitrogen rates were selected to give a range from low to high fertility and theseed rate to give a recommended rate of 300 seeds/m2 (Laverick, 1997) and alower seed rate. The effects of seed rate on yield, lodging and quality were smalland are, therefore, not presented here.0510152025303540456Yield and lodgingIncreasing the nitrogen rate increased yield with the optimum being 160 kg N/hain both years.  However, lodging became a very significant factor at nitrogen ratesabove 100 kg N/ha in 1998, although it did not occur in 1999 (Table 1).  In 1998,it must be noted that although lodging levels were high, weather conditions weregood and all plots were harvestable.  However, if conditions were poorer, thiscould have translated into considerable harvesting problems and reductions inyield and quality.  Current recommendations for winter oats are 110-140 kg N/ha(Soil Index 1).  Aberglen out-yielded Barra in 1998 but had a similar yield in1999.  Care should be taken in comparing the relative yield of these two varieties,as it is just over two seasons at one site.  More comprehensive yield performancedata is available from the Recommended List published by the Department ofAgriculture, Food and Rural Development, Backweston, Co. Kildare.Table 1: Yield (t/ha at 15 % moisture content) and lodging index, Oak Park1998 and 1999Oak Park 1998 Oak Park 1999N(kg/ha)Yield(t/ha)LodgingindexYield(t/ha)Lodgingindex70 7.34a 0.0a 8.48a -100 8.22b 5.0a 9.14b -130 8.62c 28.5b 9.82c -160 8.94d 64.6c 10.15d -190 9.08d 86.7d 10.32d -LSD 0.31 9.1 0.26VarietyAberglen 9.14 34.3 9.74 -Barra 7.74 39.7 9.43 -LSD 0.17 NS NS -Kernel contentThe effects of nitrogen rate and variety on grain quality at Oak Park 1998 and1999 are presented in Table 2.  The kernel content, while statistically significant,was only 0.5% lower at the highest rate of nitrogen than at the lowest rate ofnitrogen.  Nitrogen rate did not significantly affect the kernel content at Oak Park1999.  In both years, Aberglen had a significantly lower kernel content than Barraby 2.9% and 3.0% in 1998 and 1999, respectively.7Table 2: Effect of nitrogen rate and variety on grain quality, Oak Park1998 and 1999Oak Park 1998 Oak Park 1999N(kg/ha)Kernelcontent(%)Unhulledgrain(%)Screenings(%)Hectolitreweight(%)Kernelcontent(%)Unhulledgrain%Screenings(%)Hectolitreweight(%)70 75.1a 21.5 5.16a 55.3a 74.4 20.0a 3.61a 57.4a100 75.0a 22.5 5.77a 55.0a 74.5 17.8b 4.20b 56.9ab130 74.9a 22.1 5.55a 54.6ab 74.5 16.2c 5.18c 55.9bc160 75.0a 21.3 5.62a 54.3b 74.5 14.4d 6.31d 55.4c190 74.6b 21.1 6.81b 53.5c 74.5 14.2d 6.39d 55.3cLSD 0.3 NS 0.80 0.5 NS 1.4 0.59 1.2VarietyAberglen 73.5 34.0 6.58 54.6 73.0 25.3 6.80 55.3Barra 76.4 9.40 4.98 54.5 76.0 7.7 3.48 57.0LSD 0.2 0.8 0.43 NS 0.3 2.2 0.44 0.8a,b,c,d Means with different superscripts in the same column are significantlydifferent (P<.05)HullabilityThe percentage of grain remaining unhulled after test milling was significantlyreduced at the higher rates of nitrogen at Oak Park 1999, as at Crossnacreevy1999, therefore improving the hullability, but was not significantly affected at OakPark 1998.  The percentage of grain unhulled in Barra was lower than that ofAberglen in all experiments, in agreement with previous observations of thehullability of these varieties.Hectolitre weight and screeningsHectolitre weight declined and screenings increased in both years at the higherrates of nitrogen (Table 2).  Aberglen had higher screenings than Barra.  Thehectolitre weight of Aberglen varied relative to that of Barra.  At Oak Park 1998,Aberglen had a lower hectolitre weight, while at Oak Park in 1999 they were8similar.  Overall, Aberglen was consistently poorer in the characteristics directlyrelated to value for milling.The higher rates of nitrogen had a negative effect on quality in respect of kernelcontent, screenings and hectolitre weight but did improve hullability, although themagnitude of the changes in quality were small, especially when consideredwithin the normal ranges of production.  Agronomic practices at present, whichare tailored to achieving a balance between yield and lodging, are thereforeappropriate to achieve both yield and quality.  Variety had the largest and mostconsistent effect on quality and is the key to producing quality oats.Panicle conformation and implications for qualityIn order to further our understanding of variation in grain quality betweenvarieties and due to agronomic practices, the conformation of the oat panicle wasinvestigated.  The oat spikelet contains basal, secondary and tertiary grain.  Withinthe spikelet, the basal grain is larger (Tibelius and Klinck, 1986) and has a lowerkernel content (Hutchinson, Kent and Martin, 1952).  The basal grain was alsofound to have poorer hullability.  Variation in the percentage of basal grain wastherefore investigated to evaluate its implications for quality and whether changesin the percentage of basal grain and changes in grain weight, within eachpopulation, explained variation in quality.At Oak Park 1999, the variety Aberglen had a lower percentage of basal grain(Fig. 4) than Barra but had poorer hullability, although the differences in thepercentage of basal grain were small.  Despite Aberglen having higher screenings,it had a higher basal grain weight (Fig. 5) and a higher, but not significantly,secondary grain weight.  Therefore, the percentage of basal grain and the grainweight within the grain populations between varieties are not adequate to fullyexplain variation in screenings, although they are likely to have some influence.Further work is necessary to identify the characteristics that determine quality,such as screenings, to allow breeders to develop suitable varieties.9Fig. 4: Effect of nitrogen rate and variety on the percentage ofhand harvested grain composed of basal grain, Oak Park 1999Fig. 5: Effect of nitrogen rate and variety on the basal grain weight,Oak Park 1999Characteristics of an ideal varietyAs the effects of agronomic practices on quality were small variety selection is thekey to producing high quality oats.  An ideal variety should have a high kernelcontent, good hullability and low screenings.  A high hectolitre weight is alsorequired, as it is the primary indicator of quality used at present.  It is alsoessential for modern varieties to have high yield, stiff straw as well as goodresistance to diseases.  It is proving difficult to find a replacement variety forBarra with comparable milling quality, and it will be necessary to measure other353637383940414270 100 130 160 190N (kg/ha)AberglenBarra50515253545570 100 130 160 190N (kg/ha)AberglenBarra10parameters, as discussed in this paper, such as kernel content and hullability, toactively select for a high quality variety and to prevent unsuitable varieties makingit through the evaluation system.  Further consideration must be given to the useof hectolitre weight, as it may prevent otherwise suitable varieties, in terms ofgrain quality and agronomic characteristics, achieving Recommended List status.CONCLUSIONS♦ Hectolitre weight is not an accurate predictor of milling quality.♦ This study has developed a new test for assessing oat kernel content, which ismore rapid and cheaper than that currently available.♦ Despite its obvious importance, oat hullability has not been assessed to datein quality evaluation, due to the absence of a test procedure.  However, thisobstacle has now been overcome.♦ Using the tests developed for kernel content and hullability, the selection ofvarieties with enhanced processing characteristics can now be carried outmore precisely for Irish conditions.♦ There were significant varietal differences in kernel content and hullability.♦ Variation in hullability and screenings could not be completely explained byvariation in the percentage of basal grain and grain weight.♦ Agronomic studies indicated that nitrogen level and seed rate effects onquality were small.♦ Variety had the largest and most consistent effect on quality and is, therefore,the key to the production of high quality oats.11REFERENCESHutchinson, J.B., Kent, N.L. and Martin, M.A. (1952).  The kernel content ofoats, variation in the percentage kernel content and 1000 kernel weight within thevariety.  Journal of the National Institute of Agricultural Botany 6: 149-160.McGarel, A.S.L. and White, E.M. (1997).  Effect of disease control and plantgrowth regulator treatment on quality characteristics of spring oat cultivars.Proceedings of the V International Oat Conference and VII International BarleyGenetics Symposium, Univeristy of Saskatchewan, Saskatoon, Sask., Jul. 30 Aug. 6.  Poster #29, 86-88.Meyer, D. and Zwingelberg, H. (1981).  Investigations for using home grownoats in oat milling.  Getride. Mehl und Brot 35: 230-234.Tibelius, A.C. & Klinck, H.R. (1986).  Development and yield of oat plantsgrown from primary and secondary seeds.  Canadian Journal of Plant Science 66:299-306.

Factors Affecting Yield and Quality of Oats.

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