Variation in maturity among oats varieties and its implications for integration into the highland farming systems

Fekede Feyissa

Ethiopian Institute of Agricultural Research (EIAR), Holetta Research Center, Animal Feeds and Nutrition Research Program,
P.O.Box 2003, Addis Ababa, Ethiopia
ffeyissa@yahoo.com

Abstract

This paper presents the variation in maturity among 20 oats (Avena sativa L.) varieties assessed in terms of the durations required by the varieties to attain different physiological growth stages (boot, heading, milk, soft dough and grain maturity stages). The intention was to analyze the practical implications of differences in maturity among the varieties in view of peculiarities of the different farming systems and the various aspects of oats utilization in the highlands of Ethiopia.

There was marked variation among the varieties with respect to the durations required to attain the different growth stages. Taking the soft dough stage as a reference physiological maturity stage for forage harvest, there was on average a difference of 31 days between the early (117 days: Coker SR res 80 SA 130) and late maturing varieties (148 days: Grayalgeris). The study also revealed that most of the difference in maturity among the varieties was attributed to differences in the durations of the vegetative growth period (planting to heading) than the grain filling period. This feature has important practical implications for making proper choice of the varieties for successful integration into the farming system and feed production.

In general, the variation in maturity among the oats varieties allows the producers to grow the proper variety according to the farming system and intended purpose of production. Accordingly, early maturing varieties could be preferably grown as precursor crops to chickpea/lathyrus, to make efficient use of the small amount of moisture during belg cropping and in cases where cut-and-carry feeding is targeted to curb feed shortage during the main rainy season. On the other hand, late maturing varieties could be the better choice in cases where hay making and preservation for dry season is targeted.  

Keywords: Duration,growth stage, farming system, oats

Introduction

Oats (Avena sativa L.) is a well-adapted fodder crop grown for a long period of time in the highlands of Ethiopia. It is produced by some peri-urban dairy cattle producers and by smallholder farmers who own crossbred dairy cows. Its grain also makes part of the staple diet of human beings in some parts of central highlands of the country (Lulseged G H 1981). Oats being an annual forage crop is highly useful for integration into the prevailing mixed crop- livestock farming systems of the highlands on accounts of its short-term yielding characteristics, use in overcoming seasonal feed shortages, convenience in crop rotations and its fodder conservation characteristics. Moreover, farmers can easily grow it because its husbandry is similar to that of other cereals such as barley and wheat.

There are various cropping systems in the highlands of Ethiopia including double cropping within a season, rotational cropping and belg cropping all of which offer potential niches for integrating oats into the system. Similarly, oats has got different forms of utilization especially with respect to livestock feed (grazing, cut-and-carry green feeding, hay, silage and also as a source of cash income through sale of the green material). The grain aspect for human consumption is also an important dimension which deserves attention in oats utilization. The variation in maturity among the oats varieties has got a marked practical significance in view of peculiarities of the different cropping systems and the various aspects of oats utilization. However, previous recommendations on oats were made based on some general aspects of the varieties mainly environmental adaptation and herbage yield without an in depth information on other features of practical significance such as maturity. Therefore, this paper is aimed at assessing the variation in maturity among 20 oats varieties and highlights its practical implications for integration into the highland mixed farming systems.            

Materials and methods 

Experimental site

The experiment was conducted at Holetta Agricultural Research Center (HARC) in the central highlands of Ethiopia. The center is located at 38° 30`E, 9° 3`N and 30 km west of Addis Ababa and lies at an elevation of 2400 m above sea level. Based on an average meteorological data of 34 years (1969 – 2003) of the HARC, the annual rainfall of the area is 1066 mm with bimodal distribution, over 70% of which occurs during the main rainy season (June to September) and 30% during the small rainy season (February to April). The average annual minimum and maximum temperatures of the area are 6° to 22°C. The area is also characterized by occasional frost that occurs in the months of October to December, where temperatures below zero are recorded for few days during these months.

 The major soil type of the area is a red-brown clay loam nitosol, and analysis of composite soil sample taken from the upper 20 – 30 cm soil horizon of the specific experimental plot in this study indicated that the soil had a pH (1:1 H₂O) of 5.1, total N content of 0.2%, P content of 12.4 ppm, OM content of 2.2% and cation exchange capacity (CEC) of 17.0 meq/100 g soil. Similarly, values for the major climatic variables during the course of the experimental period (June – December 2003) were: total rainfall (686 mm), average minimum and maximum temperatures (6.5° and 21.2°C) and relative humidity of 60.6% (HARC meteorological data).

Oats varieties

Twenty oats varieties that were selected on the basis of their adaptation to the highlands of Ethiopia from previous introduction and screening works were used for the experiment. The varieties and their respective origins are shown in Table 1. 

Sowing, data collection and measurements

The varieties were sown on 24^th of June 2003 in a Randomized Complete Block Design (RCBD) with four replications. Sowing was made by drilling the seeds in rows of 0.2 m wide on 4m x 3m plots spaced 0.5 m apart. A starter dose of fertilizer at the rate of 18/46 N/P₂O₅ kg/ha (100 kg DAP/ha) was applied to all plots at sowing. A uniform seeding rate of 100 kg/ha was used for all the varieties as per previous recommendation for pure stand of oats in the highlands of Ethiopia (Astatke 1979). All the plots were hand weeded once, a month after sowing and thereafter as required based on occurrence of weeds.

The varieties were closely examined beginning from the early vegetative growth and a reliable record of the different growth stages (boot, heading, milk, soft dough and grain maturity stages) was taken. The durations required by each variety to attain the different growth stages were determined as the period in days from sowing to the respective stages.

Definitions of the terms used to describe the different growth stages are stated below:

Boot stage – the growth stage of grasses in which the head is enclosed by the sheath of the upper most (flag) leaf.

Heading stage – the growth stage when the panicle emerges out of the flag-leaf sheath.

Milk stage – stage during which a white, milk like fluid can be squeezed from the developing kernel.

Dough stage – stage during which the material pressed out of the kernel is no longer a liquid but has the consistency of dough.

Grain maturity – stage during which the plant has become completely yellow, dry and brittle and the kernel is hard.

Statistical analysis

Analysis of variance was performed using the statistical analysis system (SAS) software (SAS 2001) and mean separation was carried out using the Duncans new multiple range test.

The following general linear model was used for the analysis:

Y_ij = m + B_i + O_j+ E_ij

Where, 

Y – the measured response

m  - the overall mean

B_i  – effect of the i^th block

O_j  – effect of the j^th oats variety

E_ij – the error term associated with each Y_ij

Results and discussion 

The durations required by each oats varieties to attain the different growth stages are shown in Table 2.

The result indicated that on average the varieties require a range of 71 to 102 days, 82 to 117 days, 100 to 129 days, 118 to 149 days and 156 to 187 days to attain boot, heading, milk, soft dough and grain maturity stages, respectively. Coker SR res 80 SA 130, SRCP X 80 Ab 2252, SRCP X 80 Ab 2806, 79 Ab 382 (TX) (80 SA 94), Clintland 60 MN 16016, SRCP X 80 Ab 2291 and Ky to 78394 Canada were significantly earlier (P<0.05) than most of the varieties and on average require 71 to 75 days to attain boot stage. On the other extreme, Grayalgeris and PI – 338517 were significantly late (p<0.05) to attain boot stage than all the other varieties. Likewise, CI – 8251, PI – 244475 and PI – 5800 were significantly late (P<0.05) than most of the varieties, but significantly earlier (P<0.05) than Grayalgeris and PI – 338517 to attain a boot stage. Varieties that require short durations to attain boot stage may be useful to provide cut-and-carry fodder early as per the requirement of the farming system. The earliness trait can be further exploited by early sowing and fertilizer application. The trend in days to boot was also reflected in the durations of the subsequent growth stages. Accordingly, Grayalgeris and PI – 338517 were significantly late (P<0.05) to attain head, milk, soft dough and grain maturity stages than all the other varieties, while Coker SR res 80 SA 130 and SRCP X 80 Ab 2252 were significantly earlier (P<0.05) in achieving these stages. 

The wide range of variations recorded among the oats varieties to attain the different growth stages could allow a sound classification of the varieties as very early, early, medium, late and very late in maturity. Taking the soft dough stage as a reference stage for forage harvesting, Coker SR res 80 SA 130 and SRCP X 80 Ab 2252 can be classified as very early maturing varieties, whereas Grayalgeris and PI – 338517 can be categorized as very late maturing varieties. Similarly, varieties such as SRCP X 80 Ab 2291, 79 Ab 384 (TX) (80 SA 95), SRCP X 80 Ab 2806, 79 Ab 382 (TX) (80 SA 94) and PI – 244480 could be categorized as early maturing varieties, while CI – 8251, PI – 5800, PI – 244475 and CI – 8235 can be classified as late maturing varieties. The rest varieties can be categorized as medium maturing. The variation in maturity among the oats varieties affects timing of harvest, which in turn may affect forage yield and quality. Moreover, it is a good indication of the range of options available for utilization of oats according to priority and nature of the different farming systems. For instance, early maturing varieties can progress through different development stages at a faster rate than late maturing varieties and may be useful for double cropping system in chickpea/Lathyrus growing highland areas where the chickpea/Lathyrus is grown using residual moisture in October. Varieties with such quality are highly preferable in improved forage adoption efforts because they can be introduced without disturbing the farming system and enable the farmer to get an added benefit from the same plot of land. On the other hand, late maturing varieties may help to extend the period of green feed availability and also could be useful to be preserved as hay for periods of feed shortage.

Hellewell et al (1979) attested that the major difference in maturity among oats cultivars relate to differences in the length of the vegetative growth stage (sowing to heading), not the grain filling period (heading to grain maturity stage) and thus the fast growth of early maturing cultivars is explained in terms of a shortened vegetative growth stage rather than a shortened grain filling period. They also reported that the length of grain filling period is not associated with the relative maturity of any given cultivar as the latest maturing cultivar could have the shortest grain filling period. The result of the present study also agrees with the above finding in that the duration required for vegetative development (shown in Table 3) ranged widely from 82 to 117 days, while the duration of grain filling period ranged from 64 to 80 days among the 20 oats varieties. Moreover, late maturing varieties tended to have comparatively shorter grain filling period than early maturing varieties. 

The choice of which oats variety to grow for silage or hay, and the decision whether to harvest at the boot or dough stage are dependent on the resources available for production and the purpose for which the forage is being grown. Moreover, weather conditions and cropping patterns may dictate when the forage must be planted and when it must be harvested. With those constraints, the objective is to choose a variety and harvest stage to maximize the value of the harvested forage pertaining to its intended use. Collar and Aksland (2001) suggested that for silage and hay, the boot and dough stages are two key stages for evaluating, choosing and managing varieties of small grain forages. On account of their superior combination of yield and digestibility compared to other stages of development, boot and soft dough stages are the two recommended stages at which to harvest for silage and hay, respectively. The boot stage has been reported to be significantly higher in digestibility and protein than dough stage, but significantly lower in yield (Collar and Aksland 2001). The choosing of boot harvest versus dough harvest should include comparing the best variety for boot stage versus the best variety for dough stage, not necessarily the boot versus dough stage for any one variety. Fohner (2002) suggested that the best varieties for boot stage harvest are high tillering varieties that are late maturing and produce dense leafy growth, while the best choice for dough stage harvest are early maturing varieties with a high grain yield and high grain to stem ratio. But under Ethiopian context, early maturing varieties may be preferred for boot stage harvest and late maturing varieties for dough stage harvest. This may enable to obtain a double harvest from re-growth of the early maturing varieties and in the case of late maturing varieties, weather conditions may be conducive for hay making by the time they attain physiological maturity for harvest. Moreover, the prevailing livestock feed situation in the country demands oats varieties that attain a given harvestable stage for cut-and-carry feeding during the main rainy season and those with longer growth duration with high eventual forage yield for preservation as hay for the dry season. Early maturing oats varieties are also useful to be grown in combination with vetch as they mature in synchrony with the companion legume. Curing oats as silage has not been much experienced in the country, but there is a need to demonstrate silage making as one option of extending its utilization at least at government institutions. Similarly, although some farmers preserve oats hay, the variety they are producing, the extent of utilization and whether they harvest the crop at the recommended stage for hay is not known and requires further assessment.

Practical implications of the variation in maturity 

From double cropping point of view

Land shortage for sole cropping of a forage crop has been one of the bottlenecks for wide adoption of improved forage crops despite critical livestock feed shortage in mixed farming systems of the highlands. One of the feasible options for introducing improved forages into the system could be through integrating feed production with the cropping venture. Intercropping, rotational and/or double cropping within a season are some of the available mechanisms for feed-food crops integration. A considerable portion of land is used for growing chickpea and/or lathyrus using residual moisture in most of the highland vertisol areas. Traditionally, farmers in such areas usually plough the land once in June and leave it aside until the planting time of chickpea and/or lathyrus around mid September to early October. Growing early maturing oats varieties as a precursor to the main crops (chickpea and lathyrus) could help to optimize land productivity (in terms of feed and food production) through double cropping within a season. Highland farmers usually face critical feed shortage during the main rainy season (mainly around August and September) as the available land is covered with crops and the conserved feed reserve is exhausted. Introducing early maturing oats varieties could help to curb the feed shortage gap without competing with food crops for land in such areas.

From belg (short rainy season) cropping point of view

Belg cropping using the short rains (February to May) is common in some highlands of Ethiopia. Since belg rain is usually short, erratic and uneven, looking for crop verities that could make use of and responsive to the small amount of available moisture is the best strategy for belg growing areas. Oats is one of the preferred crops grown for a dual-purpose use (food and feed) in such areas. Farmers are very strategic in using oats during the belg season such that:

i)    if the belg rain extends for long and the moisture is felt adequate for grain setting and normal maturity, the farmers maintain and manage the oats for grain production.

ii)    if the belg rain is inadequate to carry the crop to physiological maturity for grain, the farmers divert to use as livestock feed through cut-and-carry feeding system. Green oats marketing for feed is also common by farmers in which an estimated 2kg of green material (0.5 kg DM) costs 1 Ethiopian Birr with spatial and temporal variations. Based on this estimate, about 16, 000 Ethiopia Birr (an equivalent of about 1454 USD) could be obtained from green oats grown on a hectare of land with an estimated average forage yield of 8 t DM/ha. The fact that oats could be grown on a land marginal for growing other crops allows the farmers to make efficient use of the less fertile land with considerable economic gain.             

The above scenario of using oats during the belg season could be further optimized through proper exploitation of varietial differences in maturity. 

From utilization point of view (cut-and-carry feeding Vs hay making)

The variation in maturity of the oats varieties would allow farmers and other users to make the proper choice according to their intended use. For instance, early maturing varieties could mature for forage during times when weather conditions are not conducive for hay making such as during the main rainy season. Moreover, most highland areas of Ethiopia encounter critical feed shortage during the main rainy season (July, August and September) concomitant to exhaustion of conserved feed (crop residues and hay) and coverage of the available land with crops. In view of this, growing early maturing oats varieties could be an ideal strategy to improve livestock feed supply through cut-and-carry feeding. This significantly help smallholder farmers for maintaining in-door fed crossbred milking cows and working oxen which have less access to roam around and fetch feed. On the other hand, when the intention is hay making and feed conservation, medium or late maturing varieties will be the proper choice by farmers. 

From labour distribution point of view

In the highland areas where oats is grown for human food, the varieties which mature earlier than barley are preferred by farmers as labour required for harvesting and threshing operations do not coincide with that of barley. Moreover, early maturing oats varieties are well acknowledged by the farmers due to the fact that they could mature earlier than barley and provide them with a food grain early when they are needy.    

Conclusion  

• The variation in maturity among the oats varieties allows the producers to grow the proper variety according to the farming system and intended purpose of production. Accordingly, early maturing varieties could be preferably grown as precursor crops to chickpea/lathyrus, to make efficient use of the small amount of moisture during belg cropping and in cases where cut-and-carry feeding is targeted to curb feed shortage during the main rainy season. On the other hand, late maturing varieties could be the better choice in cases where curing hay and preservation for dry season feeding is targeted. To this effect, subsequent works need to be done to create farmers awareness on merits associated with different maturity classes and their applications within the different farming systems and intended uses.    

Acknowledgements 

I would like to acknowledge the financial support by the Agricultural Research and Training Project (ARTP) of the Ethiopian Agricultural Research Organization (EARO). We are also grateful to the staff of Feeds and Nutrition Research Program at Holetta Agricultural Research Center for their keen cooperation during the field work.

References 

Astatke Haile 1979 Forage Crops and Pasture Management in the Highlands of Ethiopia. Forage and Range Bulletin No. 2, Institute of Agricultural Research, Addis Ababa, Ethiopia. 

Collar C and Aksland G 2001 Harvest stage effects on yield and quality of winter forage. In 23^rd California Alfalfa Symposium. University of California Cooperative Extension. University of California, Davis.   http://alfalfa.ucdavis.edu/+symposium/proceedings/2001/01-133.pdf

Fohner G 2002 Harvesting maximum value from small grain cereal forages. In: proceedings of Western Alfalfa and Forage conference, 11 – 13 December 2002, Sparks, NV, UC Cooperative Extension, University of California, Davis 95616 . http://www.csuchico.edu/agr/grassfedbeef/research/daily-gain/files/Harvesting%20Maximum.pdf

Hellewell K B, Stuthman D D, Markhart A H and Erwin J E 1979 Determination of physiological maturity in oats. Crop Sciences 71: 931 – 935

Lulseged G H 1981 Summary of fodder oats research undertaken by IAR. Pasture and fodder forage, Bulletin no. 2, Institute of Agricultural Research, Addis Ababa.

SAS (Statistical Analytical Systems) 2001 SAS/STAT user’s guide release 8.1. Statistical Analysis Systems Institute, Inc, Cary, NC, USA.

Received 17 July 2009; Accepted 16 August 2009; Published 1 October 2009

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