There is no known published work on the use of pea (Pisum sativum L.) in mixture with oat (Avena sativa L.) or barley (Hordeum vulgare L.) as a companion crop for the establishment of alfalfa. The objective of this field study was to determine the effect of field pea [Pi*, sativum L. var. arvense (L.) Poiret] on alfalfa (Medicago sativa L.) establishment when seeded in mixtures with oat or barley. In addition, forage yield and quality of oat and barley and their mixtures with pea were assessed. Sixteen oat and nine barley genotypes were grown alone and in mixtures with ‘Trapper’ field pea to produce oat, oat‐pea, barley, and barley‐pea companion crops. The companion crops were underseeded with ‘Blazer’ alfalfa. No single oat or barley cultivar or experimental genotype, whether mixed with pea or not, was distinctly superior for forage yield, forage quality, and subsequent alfalfa yield in the year after alfalfa establishment. Pea did not significantly affect alfalfa yield in the establishment year nor in the year after establishment. The addition of pea to oat decreased neutral detergent fiber (NDF) by 7.1 percentage units and increased crude protein (CP) by 4.4 percentage units, while adding pea to barley decreased NDF by 6.2 percentage units and increased CP by 3.0 percentage units. The oat‐pea forage mixture was significantly lower in NDF and significantly higher in CP than barley‐pea forage mixture. Although barley‐pea was highest in forage yield, we concluded that oat‐pea was the best companion crop in this study because it had superior forage quality.

Knowledge of cultivar response to N is helpful to the small grain grower, who can increase yields and profits, and to the small grain breeder, who can manipulate heritable traits to develop cultivars with improved response to N. The objective of this research was to identify morphological and physiological traits influencing grain yield response to N for three oat (Avena sativa L.) cultivars that differed in height. The cultivars were grown at five rates of N fertilizer (0, 28, 56, 84, and 112 kg N/ha) in each of three environments. ‘Stout’ was relatively short and early‐maturing, while ‘Marathon’ and ‘Lodi’ were taller and later‐maturing. The experimental design was a split plot, with N rates as whole plots and cultivars as subpplots. Stout had the largest grain yield response to N (pattern of change across rates of N) because it had better responses for spikelets per panicle and weight per kernel. Consequently, Stout accumulated more dry matter after heading. Panicle number was not positively associated with differential grain yield response to N. Stout also had thicker, heavier leaves than Lodi and Marathon, but none of the three leaf traits measured appeared to contribute significantly to the differential grain yield response among the cultivars. Determining yield component responses to N could be useful in oat breeding programs that are attempting to release cultivars which respond well to highly productive environments. Lines with favorable responses for one or more yield components should be included in a crossing program for high yield response.

Forage yield and several quality parameters of oat (Avena saliva L.) have been addressed in the literature, but the effect of N fertilizer rate on forage yield and quality of oat cultivars, and the possibility of cultivar by N interactions, has received little attention. The objective of this study was to evaluate oat cultivar responses to N fertilization when harvested as forage at heading. Nine adapted oat cultivars ranging from early to late in heading date were grown in four field environments from 1982 to 1984 with five N application rates (0, 28, 56, 84, and 112 kg ha−1). Nitrogen application rates up to 84 or 112 kg ha−1 increased forage yield and increased N concentration in two of three environments. Increasing N application rate increased neutral detergent fiber (NDF) 46 g kg−1 in one environment but decreased it slightly otherwise. In three of four environments, forage yield at heading increased (r2 = 0.66−0.94) linearly with later heading date. Nitrogen concentration generally decreased and NDF, acid detergent fiber, and acid detergent lignin concentrations increased with later heading date. The difference in NDF between the earliest and latest cultivars could affect forage utilization by affecting forage intake. In situations where high quality is important, early maturing oat cultivars might be preferable because they produce higher quality forage. Early harvest would also alleviate competition with an underseeded perennial legume earlier in the season. Application of 84 to 112 kg ha−1 of N produces maximum yields and increases N concentration with generally small effects on fiber concentrations and without increasing lodging.

The success of barley (Hordeum vulgare L.) cell and tissue culture research depends upon reliable callus culture and plant regeneration procedures. The objective of this study was to identify callus‐inducible genotypes, to evaluate media for effectiveness in promoting callus growth, and to identify genotypes capable of regenerating plants. Ninety‐one barley genotypes were evaluated for initiation and maintenance of callus growth. Forty‐five of the genotypes initiated callus, while 46 did not. Callus cultures were maintained by subculturing onto fresh media at monthly intervals. Genotypic variation was noted for longevity and rate of growth of callus cultures. Calli of several genotypes were maintained for more than 2 years. Murashige and Skoog's (MS) media promoted more callus initiation and provided better callus maintenance than media of Blaydes (B), Gamborg et al. (B5), Norstog (N), and Shenk and Hildebrandt (SH). Frequencies of callus initiation were high when either 0.5, 1.0, or 2.0 mg/L of 2,4‐D (2,4‐dichlorophenoxyacetic acid) were added to the media. There were significant genotype ✕ media interactions for callus initiation. Established calli were transferred to differentiation media to promote plant regeneration. Although there were genotypic differences in regeneration, the overall frequency was low (15%). Seventy percent of the regenerated plants were from calli of the cv. Akka and Wisconsin experimental selection X2387‐3.

A series of early and midseason isolines of oats (Avena sativa L.) contain specific crown‐rust resistance loci, which were associated with significant grain‐yield deviations when tested in rust‐free conditions. To delineate specific causes for these yield deviations, yield components were measured in the isolines and their recurrent parents in six rust‐free environments.Increased grain yields in both isolines with the crownrust resistance allele from CI 8079, an Avena sterilis L. strain from Israel, were due primarily to significantly increased tiller production. A 3.0% increase in spikelets per panicle also contributed to the increased yield of CI 9170, the early‐maturing isoline.Although each donor parent was associated with contrasting yield‐component expressions in the early and midseason backgrounds in the remaining isoline sets, causes of deviant yields were evident. An increase in panicle number contributed to grain‐yield advantages of isolines derived from CI 7171, while seed weight improvement was the most important contributor to yield improvement in the midseason isoline. The significant yield reductions of X5501 and CI 9192, the early and midseason isolines with crown‐rust resistance derived from Arena strigosa Schreb., were caused primarily by fewer spikelets per panicle.

Growth analysis studies were made on sets of four early and four midseason isolines of oats (Avena sativa L.) that had significant grain‐yield deviations from their recurrent parent in each series. These yield deviations occurred when yield genes, tightly linked to crown rust resistance genes, were transferred from unadapted Avena germplasm into the recurrent parent backgrounds through backcrossing. The higher yielding C.I. 8079‐ and C.I. 7171‐derived isolines had increased growth trait means in each series. Generally, these increases were significant in the early series but not in the midseason series, which also had smaller grain yield increases. C.I. 9170, the early C.I. 8079‐derived isoline, had a significantly higher leaf area duration (LAD), leaf area ratio (), growth rate (), and relative growth rate () than the early recurrent parent. The midseason C.I. 8079‐derived isoline, C.I. 9183, had increases for these traits, but none was significant. Leaf growth increases in the early and midseason C.I. 7171‐derived isolines, C.I. 9178 and C.I. 9188, were very small and presumably did not contribute to the grain yield advantages of these isolines. The low‐yielding C.I. 7232‐derived isolines X550I and C.I. 9192, had significantly lower LAD's, and their 's and 's were reduced, but not significantly.Although isoline‐recurrent parent growth trait differences were not always significant, the trends for these traits in the C.I. 8079‐ and C.I. 7232‐derived isolines, when compared to the recurrent parents, indicated that yield differences within these sets of closely related lines have morpho‐physiological causes that can be explained by growth analysis. LAD, , and were growth traits associated with grain yield differences in these isoline‐recurrent parent comparisons. However, C.I. 7171‐derived isolines had higher grain yields but similar LAD's when compared to their recurrent parents.

Several researchers in the U. S. and Canada have investigated the effect of row spacing on yield and other agronomic traits of small grains with variable results. The objective of this study was to compare the performance of spring barley (Hordeum vulgare L. emend Bowden) seeded in a very narrow row spacing (7.5 cm) with two row spacings (15 and 30 cm) commonly used in production agriculture and in experimental research. Three genotypes were planted at Madison, WI, in 1975 and 1976, in a St. Charles silt loam soil (Typic Hapludalf, fine‐silty, mixed, mesic) and at Arlington, WI, in 1977, in a Plano silt loam soil (Typic Arguidoll, fine‐silty, mixed, mesic). A seeding rate of 134 kg/ha was used in all row spacings. The three environments had yield levels ranging from high to low, due primarily to differences in rainfall. When results were combined over environments, 7.5 cm‐rows yielded 4% more grain than 15‐cm rows and 12% more grain than 30‐cm rows. These differences were significant, but differences were not always significant for a single environment. Straw yield response to row spacing was similar in magnitude to the grain yield response. The increased grain and straw yields in narrower rows were attributed to greater tillering. There was significantly less lodging in 7.5‐cm rows than in 15 and 30‐cm rows in the two environments in which lodging occurred. Although the grain and straw yield improvements in this study may not be large enough to encourage changing to grain drills with a row spacing narrower than 15 cm, the reduced lodging in 7.5‐cm rows may be an added advantage when lodging is substantial.

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