- Authors:
- Qureshi, Z. A.
- Neibling, H.
- Source: Agricultural Water Management
- Volume: 96
- Issue: 1
- Year: 2009
- Summary: Agricultural production in irrigated areas is becoming more water-constrained. Scheduling the timing of the last irrigation on cereals is one effective method of reducing seasonal water use while maintaining crop yield and quality. The last irrigation application time and its impact on two-row malting barley ( Hordeum distichum cv. Moravian 37) yield, quality, and economic benefits were studied in the 2000, 2001, and 2002 cropping seasons. Irrigation was stopped for the season at Milk, pre-Soft Dough, Soft Dough, and post-Soft Dough grain formation stages. The Soft Dough water cutoff treatment produced the highest grain yield of two-row spring malting barley. Water cutoff before or after Soft Dough stage reduced the grain yield significantly at P
- Authors:
- Source: Crop Science
- Volume: 49
- Issue: 3
- Year: 2009
- Summary: Nitrogen uptake and partitioning in oat ( Avena sativa L.) are not well documented. A greenhouse study was conducted to determine the critical timing of N supply on the growth, N uptake, and partitioning. Plants grown in plastic pots were subjected to five N fertilization regimes: (i) control, N supply from seedling to physiological maturity (PM); (ii) N supply from seedling to flag leaf; (iii) N supply from flag leaf to PM; (iv) N supply from seedling to heading; and (v) N supply from heading to PM. Leaf chlorophyll content, plant dry matter (DM), and N uptake and accumulation were measured. Total plant DM was 21% greater for naked 'VAO-2' than for covered 'Prescott', while both genotypes produced similar grain yields. Varietal differences in total plant N were significant ( P
- Authors:
- Source: Geoderma
- Volume: 149
- Issue: 3/4
- Year: 2009
- Summary: Management of a black oat ( Avena strigosa [Schreb.]) cover crop by mowing method (none, flail mowing, or sickle bar mowing) affected soil micro environmental conditions and soil microbial and chemical properties. Soil temperatures at depths of 0, 5, 10 and 20 cm were highest in flail mowed treatment plots (up to near 45°C at 5 cm depth), followed by sickle bar mowed plots (averaging 10°C lower at 5 cm depth). Lowest soil temperatures were maintained in plots that were not mowed; averaging 5°C lower at 5 cm depth than the sickle bar mowed plots. Increasing temperature convergence was observed below 5 cm, with the highest temperature (flail mowed treatment) at 32°C and the lowest (not mowed) at 27°C. Microbial biomass increased significantly ( P150 mg C kg -1 in the early fall. beta-glucosidase and alkaline phosphatase activities decreased slowly throughout the experiment, and were significantly greater ( P
- Authors:
- Vyn, T.
- McIntyre, L.
- Brewer, J.
- West, T.
- Santini, J.
- Boomsma, C.
- Source: Soil & Tillage Research
- Volume: 106
- Issue: 2
- Year: 2009
- Summary: Research emphasizing slower plant growth and delayed maturity in continuous maize ( Zea mays L.), no-till (MM-NT) systems has often led to the conclusion that lower grain yields in this environment are associated with reduced plant heights. Yet prior research has shown that early-season and mature plants are not always shorter in MM-NT systems, suggesting that overall plant height may not be an accurate morphometric indicator of decreased yield in MM-NT environments. Given that plant-to-plant morpho-physiological uniformity is strongly associated with higher yield in maize, we hypothesized that greater plant height variability would provide a better agronomic explanation for yield loss in MM-NT environments than overall plant height reductions. This 14-year study primarily examined the effects of crop rotation {maize-soybean [ Glycine max (L.) Merr.] and continuous maize} and tillage system (no-till and moldboard plow) on the yield, 4-week plant population, and 4- and 8-week plant height and plant height variability of a single maize cultivar. Due to sizeable year-to-year variation, actual crop response means for the MM-NT; maize-soybean, no-till (MB-NT); and continuous maize, moldboard plow (MM-PL) treatment combinations were expressed relative to the accompanying means for the maize-soybean, moldboard plow (MB-PL) treatment. In numerous years, the MM-NT system exhibited reduced actual and relative yields and lower 4- and 8-week plant heights compared to the other treatment combinations. Both actual and relative 4- and 8-week plant height variability were rarely greatest for the MM-NT treatment, and in only a few years were actual and/or relative plant density lowest for this system. However, single-factor regression analyses between relative yield and the aforementioned relative agronomic measures revealed that a decline in relative MM-NT yield was most strongly associated with an increase in relative 4-week plant height variability. Multi-factor regression analyses between relative yield, relative 4-week plant height variability, and various weather parameters suggested that this strong inverse relationship was potentially a manifestation of (i) non-uniform germination, emergence, and early seedling growth and (ii) later-season intra-specific competition. Regression analyses between relative 4-week plant height variability and various weather parameters suggested that phenomenon (i) was potentially promoted by cool and moist or warm and dry pre-plant weather conditions while phenomenon (ii) was possibly encouraged by low precipitation and/or high temperatures during rapid stem elongation. While MM-NT systems should be managed to limit plant density reductions and minimize growth and developmental delays, increased focus should be placed on minimizing the occurrence of plant-to-plant variability in these environments.
- Authors:
- Darbyshire, S.
- Clements, D.
- DiTommaso, A.
- Dauer, J.
- Source: Canadian Journal of Plant Science
- Volume: 89
- Issue: 5
- Year: 2009
- Summary: Hemp dogbane, Apocynum cannabinum (Apocynaceae), is a perennial herb with white to greenish flowers in terminal clusters that produces pencil-like pods 12-20 cm long. A highly variable plant, A. cannabinum may be distinguished from spreading dogbane ( Apocynum androsaemifolium) by its shorter corolla (2-6 mm compared with 5-10 mm), erect greenish-white petals (compared with recurved or spreading pinkish petals), seeds more than 3 mm long (compared with seeds less than 3 mm), and more erect leaves (compared with spreading or drooping leaves), although frequent hybridization between the two species obscures the identity of some individuals. Hemp dogbane is native to the United States and southern Canada, but most abundant in the upper Mississippi River Valley and east to the Atlantic coast. It has been increasing in other areas, and becoming more of a problem where conservation tillage is adopted. It infests crops such as corn ( Zea mays), soybeans ( Glycine max), wheat ( Triticum aestivum), sorghum ( Sorghum bicolor) and forages, and may cause livestock poisoning due to cardiac glycosides within its milky sap (but livestock generally avoid it). Potential medicinal uses of these compounds have been investigated, and the roots are a source of fibre. Control of A. cannabinum with various herbicides is difficult due to a thick cuticle, and one solution may be to target susceptible stages, such as seedlings or early spring growth. Cultivation may also control A. cannabinum, but care must be taken not to promote the proliferation of the plant through regrowth from fragmented roots and rhizomes. Rotation with alfalfa also reduces populations of A. cannabinum.
- Authors:
- Gentry, T.
- Aitkenhead-Peterson, J.
- Gonzalez-Chavez, M.
- Zuberer, D.
- Hons, F.
- Loeppert, R.
- Source: Soil & Tillage Research
- Volume: 106
- Issue: 2
- Year: 2009
- Summary: Tillage and crop rotation/intensity can influence soil biological properties and relevant soil processes including C sequestration. This study determined the effects of long-term (25 years) no till (NT) and conventional tillage (CT) management and cropping sequence [continuous wheat (CW; Triticum aestivum L.) and a rotation of sorghum ( Sorghum bicolor L. Moench), wheat and soybean (RW; Glycine max L. Merr)] on soil microbial community structure and labile and recalcitrant microbial bio-products in central Texas. Fatty acid methyl ester (FAME) profiles, microbial biomass (MB-C, -N and -P), hot water extractable soil carbohydrates (HWE-SC) and easily extracted- (EE-) and total-glomalin-related soil proteins (T-GRSP) were analyzed. Principal component analysis of the FAME data indicated that crop management modified and selected microbial populations. In general, NT-RW resulted in the greatest richness and biodiversity of the total microbial community, soil organic C, MB-P, HWE-SC, EE- and T-GRSP. No tillage increased labile and more recalcitrant bio-products, soil organic C and total N compared to CT. The soil microbial biomass C:N:P ratio, an indicator of ecosystem nutrient limitation, suggested that the CT-RW treatment may have a soil P limitation, which was not observed in the other treatments. The treatments preferentially selected for different microbial communities, which generated microbial products that significantly influenced soil C and N retention. Our results suggested that NT in conjunction with crop rotation (RW) can be recommended for increased soil C sequestration.
- Authors:
- Diaz-Zorita, M.
- Pena-Yewtukhiw, E.
- Grove, J.
- Blevins, R.
- Source: Better Crops with Plant Food
- Volume: 93
- Issue: 4
- Year: 2009
- Summary: This long-term Kentucky study evaluated the impact of tillage and N rates on crop yield and soil organic matter (SOM). After 29 years of continuous corn with a winter cereal cover crop, the combination of no-till cropping and fertilizer N use resulted in SOM levels similar to those in adjacent grass sod. There was no evidence that fertilizer N caused SOM loss.
- Authors:
- Elliott, N.
- Michels, J.
- Ansley, J.
- Mirik, M.
- Source: Southwestern Entomologist
- Volume: 34
- Issue: 2
- Year: 2009
- Summary: The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a severe pest of wheat, Triticum aestivum L.; barley, Hordeum vulgare L.; other small grains; and grasses. Although the Russian wheat aphid is a significant pest of small grains, its feeding effects on grain yield and vegetative biomass in large-scale wheat fields have not been well documented. Data were collected for 3 years in dryland and irrigated wheat fields in Texas and Oklahoma. The insect reduced grain yield 50.2 to 82.9% and biomass by 55.4 to 76.5%. These results suggested that winter wheat suffers significant economic loss from Russian wheat aphid.
- Authors:
- Rhinhart, K.
- Ong, C.
- Ohm, J.
- Flowers, M.
- Corey, A.
- Petrie, S.
- Hayes, P.
- Rey, J.
- Ross, A.
- Source: Crop Science
- Volume: 49
- Issue: 1
- Year: 2009
- Summary: Grain beta-glucan content is the most important attribute for barley ( Hordeum vulgare L.) varieties destined for the human food market. This trait is important because of the blood glucose and cholesterol-reducing properties of beta-glucans. High levels of grain protein content, test weight, and seed size and endosperm color may also add value. Seed yield potential, in part, determines the economic feasibility of producing human food varieties. To determine the potential of food barley production in the dryland production areas of the Pacific Northwest of the United States, 33 cultivars and advanced lines reported to vary in beta-glucan content were grown in 2006 and 2007 at two locations in northeastern Oregon under dryland cropping conditions. Seed yield, test weight, percentage of plump kernels, grain beta-glucan, and grain protein were measured on replicated samples from the four environments, allowing for assessment of average performance as well as genotype * environment interaction. Estimates of variance components showed that ~66% of the variability in beta-glucan content was attributable to genotype. Cultivars and lines with waxy starch had an average beta-glucan value of 55 g kg -1 compared with 35 g kg -1 for cultivars and lines with nonwaxy starch. We found significant two- and three-way interactions, but these accounted for much less of the total variation in the measured phenotypes than the main effects of variety, year, and location. Hulless accessions produced an average of 3580 kg grain ha -1 compared with 4260 kg grain ha -1 for the hulled accessions. Hulled, waxy-starch varieties appear to have the greatest agronomic potential for dryland production, as they combine high yield potential and grain beta-glucan percentage.
- Authors:
- Jabro, J.
- Caesar-TonThat, T.
- Sainju, U.
- Source: Soil Science Society of America Journal
- Volume: 73
- Issue: 5
- Year: 2009
- Summary: Tillage and cropping sequence may influence C and N sequestration, microbial activities, and N mineralization in dryland soil aggregates. We evaluated the 21-yr effect of tillage and cropping sequence combinations on C and N fractions in aggregates of a Dooley sandy loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) at the 0- to 20-cm depth in eastern Montana. Tillage and cropping sequences were no-tilled continuous spring wheat (NTCW) ( Triticum aestivum L.), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat-barley ( Hordeum vulgare L.) (1984-1999) followed by spring wheat-pea ( Pisum sativum L.)(2000-2004)(FSTW-B/P), and spring-tilled spring wheat-fallow (STW-F). Carbon and N fractions were soil organic C (SOC), total N (STN), particulate organic C and N (POC and PON), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), NH 4-N, and NO 3-N. Aggregate proportion was greater in NTCW than in FSTCW in the 4.75- to 2.00-mm aggregate-size class at 0 to 5 cm but was greater in STW-F than in STCW in the 2.00- to 0.25-mm size class at 5 to 20 cm. After 21 yr, STW-F reduced SOC, STN, POC, and PON concentrations in aggregates by 34 to 42% at 0- to 5-cm and by 20 to 32% at 5- to 20-cm compared with NTCW and STCW. The PCM and MBC were greater in NTCW and STCW than in STW-F in the
