Search

Thirteen hard red winter wheat cultivars were evaluated for their ability to suppress summer annual weeds in grain production systems near North Platte, NE, from 1993 through 1997. ‘Turkey’, a 125-yr-old landrace selection, suppressed both broadleaf and grass weeds more than other cultivars. Some relatively new cultivars, such as ‘Arapahoe’, ‘Jules’, ‘Pronghorn’, and ‘Vista’ suppressed summer annual grasses almost as well as Turkey. Total weed density was negatively correlated with number of winter wheat stems/m2, mature winter wheat height, and lodging. Weed density after wheat harvest was positively correlated with delay in winter wheat seeding date and was negatively correlated with precipitation 0 to 30 d after winter wheat seeding, during tillering, tillering to boot stage, and heading to maturity stage. Mean air temperature 0 to 30 d after wheat seeding was positively correlated with weed density. In the spring, weed density was positively correlated with temperatures during the tillering stage, tillering to boot stage, and heading to maturity stage. Stinkgrass and witchgrass densities were positively correlated with severity of wheat leaf rust. The highest grain-producing cultivars included three medium height cultivars ‘Alliance’, Arapahoe, and ‘Niobrara’. Alliance wheat produced 53% more grain than Turkey, and the other two produced 43% more grain.

Iron deficiency chlorosis (FeDC) is a major problem for many crop and ornamental plants in Nebraska. The most severe conditions are in river valleys where soil pH may range from pH 5.0 or less, to areas with pH values over 10. The problem of FeDC in various degrees affects nearly 500,000 ha of corn (Zea mays L.) in Nebraska. On a global scale, millions of hectares are affected. Soils in most fields are not homogeneous, thus high pH areas, where crop chlorosis prevails, are intermixed with areas of excellent soils that are capable of producing high yields. Corn breeding germplasms and experimental and commercial corn hybrids were grown on four sites of Cozad silt loam, saline‐sodic (Typic Haplustolls) with pH ranges from 7.4 to 8.6. Marked differences in response to the pH 8.6 site resulted in no surviving plants in some genotypes to relatively normal appearing growth in others. No hybrids were found that yielded as well on the pH 8.6 soils as they did on better soils. However, several that did be...

In Nebraska, nearly 0.4 million hectares (ha) of maize (Zea mays L.) are subjected to varying degrees of iron (Fe) chlorosis from high pH soil. A factorial design with two maize varieties (tolerant and non‐tolerant) and seed row applied Fe treatments with four replications was used on three soil areas of Cozad silt loam with pHs of 8.6, 8.2, and 7.7. Iron treatments included a check, seed row applied FeSO4•7H2O, FeEDDHA, dried granular FeSO4‐polyacrylamide gel and foliar sprays of 1.5% FeSO4•7H2O. Chlorophyll meter readings at V8 and V10 separated treatment effects on the pH 8.6 site and were highly correlated with yield. In 1993, all Fe treatments on the pH 8.6 site produced significant yield increases on both varieties except the foliar treatment and FeEDDHA on the non‐tolerant hybrid. The FeSO4‐polyacrylamide gel was especially effective, but was not available in 1994. Most Fe treatments significantly increased yields on the pH 8.2 and 8.6 sites, but not the pH 7.7 site. In 1994, most Fe treat...

Winter wheat cultivars that are competitive with weeds help control weeds in crop rotations. Ten winter wheat cultivars were evaluated for interference with summer annual grasses in the wheat and the subsequent grain sorghum crop in a winter wheat-ecofallow sorghum-fallow rotation in which there are two 10–mo fallow periods and two crops in 3 yr during 1983 to 1987. The medium–tall (100 to 109 cm tall) and medium–statured (90 to 99 cm tall) winter wheat cultivars (‘Buckskin’, ‘Siouxland’, ‘Lancota’, ‘Centurk 78’, and ‘Brule’) were more competitive than medium-short (80 to 89 cm tall) and short (68 to 79 cm tall) cultivars (‘Eagle’, ‘Homestead’, ‘Colt’, ‘Vona’, and ‘TAM 101’). Atrazine plus paraquat was applied to all cultivars 30 d after wheat harvest. When grain sorghum was planted in areas previously seeded with medium–tall and medium-statured winter wheat, summer annual grass weed biomass in sorghum was 61% less than in grain sorghum seeded into areas previously planted with medium-short and short wheat cultivars. Use of pendimethalin plus 2,4–D in winter wheat and glyphosate plus alachlor in grain sorghum eliminated differences in summer annual grass weed density and weed biomass among wheat cultivars. Sorghum grain yields were improved 7% when herbicides were used in the winter wheat and sorghum but value of the increase was less than cost of herbicides. Substituting less costly herbicides for herbicides used in this study still would not have been enough to pay for cost of herbicides for five cultivars. Grain sorghum grown on weed–free stubble of medium–tall and medium–statured winter wheat produced more grain than grain sorghum grown after medium–short and short-statured winter wheat by 5%. Volunteer wheat density during the fallow period following grain sorghum was lower in areas originally seeded to Centurk 78 and Siouxland wheat while volunteer wheat density was higher in areas planted to Homestead and Vona.

Declining groundwater levels in irrigated areas of the Great Plains may require a shift to limited irrigation or a return to dryland production. A field study was developed to determine the yields that could be attained in minimum till cropping systems that included winter wheat (Triticum aestivum L.), corn (Zea mays L.), soybean [Glycine max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench] under dryland farming, and limited and full irrigation. The limited irrigation allocation was 6 in./crop/year. The experiment began in 1981 on a Cozad silt loam (fine-silty, mixed, mesic Fluventic Haplustoll) at North Platte, NE, where average annual precipitation was 19.4 in. Management practices for fertilizer, herbicide, variety selection, and pest management were modified as improved varieties, technology, and products became available [...]

Iron deficiency chlorosis (FeDC) in various degrees affects nearly 500,000 ha of corn (Zea mays L.) in Nebraska, primarily in the river valleys, but also on eroded uplands. Corn hybrids produced from 27 public released and 45 experimental inbreds were grown on a Cozad silt loam, saline‐sodic (Typic Haplustolls). This soil is slightly calcareous with average pH of 8.3, organic matter 1.8%, DTPA‐iron 2.59 ppm, SAR 1.75, and electrical conductivity (EC) of 1.97 in the top 28 cm. Salinity and sodium increase in the next 28 cm with pH at 8.6, SAR 3.44, and EC 2.12. Under these conditions, corn grain yields ranged from 0 to nearly 7600 kg/ha. Yields of the most tolerant hybrids were still only 60–65% of those hybrids grown on a Cozad silt loam with lower salinity and sodium. Susceptibility to FeDC is very genotype specific with the most extreme case being MO17 by N192 yielding 6400 kg/ha, while MO17 by N195 gave 0 yield. Average yield of the six hybrids made with N139 as a parent was 398 kg/ha. Several...

A maize inbred line (Purple 3036–1) with tolerance to nigh‐pH soils was crossed with susceptible homozygous translocation stocks that marked all chromosome arms, except the short arms of 3 and 7 and the long arm or 10. F2’s and test crosses to the appropriate translocation stocks were used in the analysis. A randomized complete block design with eight replications was used to evaluate the height difference between paired rows grown from normal and mutant seeds. Six replications were grown on land that had formerly been a creek bed and ranged in pH from 8.2 to 9.1 at 0 to 20 cm. Two replications were grown in a nearby field with a pH of 7.9 at 0 to 20 cm as a control. The treatment design was a split‐split‐plot with the translocation being the whole plot, the F2 and test cross involving the same translocation as the subplot, and the normal and mutant (sugary or waxy) rows as the sub‐subplot. The results were evaluated using a t‐test that combined data from both the F2 and the test cross of a parti...

Twenty-five winter wheat (Triticum aestivumL.) cultivars were sprayed with herbicides when in the tillering stage in April at North Platte, NE. In 1978, ‘Lindon’ and ‘Vona’ stands were reduced and grain yields of ‘Larned′, Lindon, ‘Roughrider′, 'Sage′, 'Scout 66′, 'Sentinel′, ‘Turkey′, and Vona cultivars were reduced by metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] plus pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] at 0.3 plus 2.8 kg ai/ha. There were no differences among cultivars in response to herbicides in 1979, 1981, and 1982. During 1980, wheat was more tolerant to a mixture of pendimethalin and 2,4-D [(2,4-dichlorophenoxy)acetic acid] than metribuzin plus pendimethalin. In 1981 and 1982, combinations of 2,4-D with pendimethalin or metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] did not reduce wheat yields. The mixture of pendimethalin plus 2,4-D performed satisfactorily in 4 yr of use.

Maize (Zea mays L.) germplasm with good tolerance to high pH soil has been noted. This tolerance was found in agronomically poor germplasm. Efforts are underway to determine the genetics involved in the tolerance and its transfer to more elite lines. The germplasm was evaluated in 1985 under pH environments ranging from 8.0 to 9.6 at the 0–20 cm depth and 8.3 to 10.0 at the 20–40 depth.

Several fungal species were isolated from stalks and roots of grain sorghum (Sorghum bicolor) during the 1980 and 1981 growing seasons. Fungi were isolated with increasing frequency from anthesis through the grain-filling period. Fusarium moniliforme was the predominant species recovered from stalks. Several other Fusarium species were also found along with Alternaria spp. and Nigrospora sp. The fungi most commonly isolated from roots were F. equiseti, Trichoderma spp., and Alternaria spp. A similar sequence of colonization was observed in stalk tissue during the two seasons. Roots also appeared to be colonized by fungi in a pronounced sequence