Frequent inquiries about the response of small grains to atrazine (2‐chloro‐4.ethylamino‐6‐isopropylamino‐s‐triazinc) have been made, but research in this area has been very limited. If atrazine carryover is expected, harley (Hordeum vulgate L. emend Bowden) and spring wheat (Triticum aestivum L. em Thell) might be more suitable small grains to grow if they produced more grain and straw in residual atrazine than oats (Avena sativa L.). The objectives of this research were to evaluate the response of barley and spring wheat to atrazlne, to compare the response of these two small grains to the response of oats, and to test for genotyplc differences for grain yield response to atrazine in barley and spring wheat.Atrazine applications of 0, 1.12, 2.24, 3.36, and 4.48 kg/ha were applied postemergence to corn (Zea mays L.) in 1975, and the small grains were sown during the spring of 1976. This procedure was repeated in 1976 and 1977. The soil was a silt loam (Typic Arguidoll, finesilty, mixed, mesic) with 3.5 to 4.0% organic matter.Grain and straw yields of all genotypes were reduced by atrazine carryover, and species differences were evident. Barley produced higher grain and straw yields in residual atrazine than spring wheat in both 1976 and 1977. Oats, which were not included in 1976 comparisons, also had higher grain and straw yields than spring wheat in 1977. Oats did not yield as much grain and straw as barley in high levels of residual atrazine in 1977, but on the basis of tolerance (yield in soil containing atrazine/yield in soil with no atrazine), there was little difference between barley and oats. However, barley was significantly more tolerant of atrazine than spring wheat on the basis of seedling dry matter production in a greenhouse test. Variation among genotypes for response to atrazine in the 2 years of testing was limited in both barley and spring wheat.The results of this research indicate that if small grains are grown in soil with an anticipated atrazine carryover problem, barley would be preferable to oats. and both harley and oats would be preferable to spring wheat.
This study was a continuation of an earlier study which showed that spring barley (Hordeum vulgare L. and H. distichum L.) produced higher grain and straw yields in soil containing atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) carryover than spring oats (Avena sativa L.). and spring wheat (Triticum aestivum L.). The objective of this study was to evaluate the effect of atrazine carryover on malting quality of barley.In 1976 and 1977, six barley genotypes were grown to maturity in soil containing atrazine carryover, and the seed was analyzed for malting quality. Atrazine treatments (0, 1.12, 2.24, 3.36, and 4.48 kg of active ingredient/ha) had been applied postemergence to corn (Zea mays L.) 1 year prior to growing the barleys.Light atrazine carryover had a minor effect on malting quality, but heavy carryover reduced quality considerably. Heavy atrazine carryover reduced kernel weight, kernel plumpness, kernel color, malt extract, and wort color, and increased barley and wort protein percentages, diastatic power, and alpha amylase activity. With the possible exception of the increases in the two enzyme systems, all of these changes detracted from malting quality.Although genotype × atrazine level interactions were significant for several quality parameters, only one interaction had special importance. In both years, the genotype ‘Morex’ maintained a high malt extract despite increasing atrazine carryover.
The popularity of atrazine [2‐chloro‐4‐(ethylamino)‐6‐ (isopropylamino)‐s‐triazine], a persistent corn (Zea mays L.) herbicide, has caused problems for oats (Avena sativa L.) grown in rotation with corn. Despite frequent inquiries about the response of oats to atrazine, very little testing for cultivar differences to atrazine has been conducted. Therefoxe, the objective of this study was to evaluate the response of current oat genotypes to atrazine. Twenty oat genotypes were evaluated for response to atrazine for 2 years. Five atrazine treatments, 0, 1.12, 2.24, 3.36, and 4.48 kg/ha, were applied postemergence to corn land during each of the years prior to growing the oats. Atrazine damage to oats grown in 1976 was light because of wet conditions during the last half of 1975, while damage to oats grown in 1977 was more severe because of dry conditions during the last half of 1976. Grain and straw yield responses of the genotypes were evaluated on the combined data from the 2 years of testing with a regression procedure. Tolerant genotypes were expected to have a high mean and a regression coefficient less negative than −1.0, while intolerant genotypes were expected to have a low mean and a regression coefficient more negative than −1.0. There was significant genetic variability for grain yield response to atrazine. Froker, Lang, Mackinaw, X2078‐1, and X1839‐1 were more tolerant of atrazine than Dal, Lyon, Otee, and Allen. There also was significant variability for straw yield response to atrazine, but grain and straw yield responses (regression coefficients) were not significantly correlated. Straw yield response to atrazine was closely associated with plant height. The influence of atrazine on kernel quality was evaluated in a subset of eight genotypes. Groat protein percentage was increased by higher levels of residual atrazine, but groat protein yields were reduced because of the grain yield reductions. Groat percentage and 100‐seed weight were not reduced in 1976 when atrazine damage was light, but both were reduced in 1977 when damage was severe. Although there was significant genetic variability for response to atrazine among the 20 genotypes tested, the variability probably is not sufficient to warrant intercrossing them in an effort to develop genotypes with improved tolerance. A thorough search of the World Oat Collection for more tolerant genotypes is recommended.
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