Early Planting Dates Research Articles

気候温暖化が我が国の穀物生産に及ぼす影響

The purpose of this study is to assess the possible impacts of climatic warming on rice, maize and wheat production in Japan. Crop models (CERES-Rice, -Maize and -Wheat) were used to simulate the possible changes in crop yields and growing season lengths under different climate change scenarios derived from three general circulation models (GCMs). Increased temperature resulted in decrease in simulated crop yields and shortened growing season lengths in many regions under the present management systems. While the direct beneficial effects of CO2 may compensate for the yield decreases in central and northern Japan, the effects did not compensate for the yield decreases in Kyushu. The changes in crop yield varied largely among the GCM scenarios. In general, the GISS scenario is very favorable for crop production in Japan, but the UKMO scenario is not favorable, showing a considerable yield decrease. Wheat production would be very vulnerable to any GCMs climate change scenarios. Early planting and irrigation are possible adaptation strategies of the management systems to climate change. In most cases, simulated yields increased under climate change conditions if an early planting date was adopted; however, in Kyushu because of high temperature stress, an earlier planting did not improve simulated yields, and the introduction of new cultivars better adapted to the climate change conditions would be required.

Physiological responses of banana (MusaAAA; Cavendish sub-group) in the subtropics. IV. Comparison between tissue culture and conventional planting material during the first months of development

SummaryUniform tissue culture (TC) and conventional sucker (CON) planting material of cv. Williams were planted in adjacent rows on a late (28 January 1991) and an early (28 October 1991) planting date (PD) and managed similarly. Measurements of photosynthesis rate (A) between TC and CON plants were taken with portable photosynthesis measuring equipment on a total of five plants per month for each planting material type and repeated twice per month over the first six months after planting. The respective plants on which A was measured were analyzed for dry-mass production and carbohydrate status of all plant parts at the end of each month. TC plants produced a 77% larger root system than CON after five months of development, following October PD. During the same time TC plants had developed a 99% greater mean functional leaf area. A further advantage of TC plants was the earlier attainment of increased assimilation potential, having an average of higher A than CON during the first three months of developm...

Planting Date and Row Width Effect on Severity of Brown Stem Rot and Soybean Productivity

Early planting date and narrow rows increase the yield potential of soybean [Glycine max (L.) Merr.]. The purpose of this study was to determine the effect of these management practices on severity of, and yield loss due to, brown stem rot (BSR) (caused by Phialophora gregata W. Gams). Field studies were conducted for 2 yr (1988 and 1989) at the Hancock, WI, Agricultural Research Station, on a Plainfield loamy sand (mixed, mesic Typic Udipsamments). Treatments were three planting dates (1 May, 15 May, and 30 May), two row widths (7 and 30 in.), and two cultivars (BSR-susceptible cv. Corsoy 79 and BSR-resistant cv. BSR 101). Stem and foliar symptoms were less severe on plants in the delayed planting [...]

168 EFFECT OF PLANTING DATE AND ROW COVER UTILIZATION ON YIELD OF `CHANDLER' IN A HIGH-DENSITY ANNUAL SYSTEM

An RCB (4 replicates - 4 m plots) planting of `Chandler' was established to test the effects of planting date and floating row covers (FRC) in a high density strawberry planting system under NJ conditions. Transplant “plugs” from runner tips were planted on a double row (0.5 m × 0.3 m) on a raised plastic mulch bed (1.5 m centers), with trickle irrigation. Treatments included: plant 9/18/91 w/FRC on 10/7/92; plant 9/18/91 w/FRC on 12/2/92; plant 9/18/91 w/noFRC; plant 10/7/91 w/noFRC; plant 9/14/92 w/FRC on 10/7/92; plant 9/14/92 w/noFRC. In 1992, `Chandler' yield increased with earlier planting date and earlier FRC application (range: 8,600 to 13,400 kg/ha). There were no significant differences in cull or fruit weight. In 1993, there were no significant differences in 2nd year yield for 1991 treatments (range: 19,198 to 20,531 kg/ha). However, the 1992 treatments again showed the benefit of FRC (range: 13,437 to 20,531 kg/ha) for improved first year production. One year old plots had significantly larger average fruit weight than two year plots (range: 10.3 to 13.7 g). Early planting date with early applied FRC was the best treatment, combining high yield and good fruit weight.

213 A COMPARISON OF STRATEGIES FOR SCHEDULING IRRIGATION OF VEGETABLES

The effect of irrigation scheduling method (variable crop factor, 1; constant crop factor, 2; empirical, 3), soil water tension (25, 50, 75kPa SWT), tillage (disc arrow, DA, moldboard plow, MP) and planting dates (PD) on total irrigation (TI), number of irrigations (NI), useful (UR) and lost rainfall (LR) was studied using a Pascal program that simulated water budgets of 720 crops of snap bean over 10 years. NI and TI were significantly (p<0.01) lower with met.1. Met.3 had the lowest LR and highest UR, but did not allow the complete calculation of the water balance. TI was significantly higher at 25kPa. MP tillage requested fewer NI and less TI, had lower LR and higher UR. Early PD requested fewer NI and TI, and had higher LR. Hence, when water supply was not limiting and weather data were available, a combination of Met.1, MP at any PD provided a continuous supply of water to the crop while controlling water deficit.

Response of forage yield and yield components to planting date and silage/pasture management in spring seeded winter cereal/spring oat cropping systems

Spring-planted mixtures of spring and winter cereals in a silage/fall pasture system have been shown to extend the grazing season in the Parkland of the Canadian prairies. Experiments were conducted at Lacombe, Alberta to determine the effects of planting date on yield and yield components of spring-seeded spring oat (Avena sativa L.), winter wheat (Triticum aestivum L.), winter triticale (X Triticosecale Wittmack) and winter rye (Secale cereale L.). The cereals were grown as monocrops or as binary mixtures of the oat and winter cereals. Treatments were planted in early May and mid-June and harvested twice for forage. The initial harvest for early and late planting dates occurred when oat reached the early-milk and heading stages, respectively. Regrowth was harvested in mid- to late September. The planting date x treatment interaction did not affect (P ≤ 0.05) annual yield (initial + regrowth) even though oat was harvested at different developmental stages. Averaged over treatments, late planting reduced annual yield by 42%. The annual yields ranked: mixtures = oat monocrop > winter cereals. Late planting date reduced the initial yield of all treatments, but the winter monocrops were reduced less than oat. Oat dominated the initial yield of all mixtures. Although oat tiller density was lower in the mixtures than monocropped oat at the initial cut, oat constituted a greater proportion of the mixture than would have been expected from the seeding ratio (1:1). A larger tiller weight in the oat mixture vs. the monocrop may have compensated for low tiller density in the mixture. Mixture regrowth yields tended to be greater in late-planted treatments and were dominated by the winter cereals. Although the winter cereal component of the mixture had more tillers at the regrowth cut, they still had lower yields when compared with their respective monocrops. Thus, late planting reduced annual yields of mixtures and monocrops, but did not limit regrowth of winter cereals in mixtures given equal regrowth periods. Key words: Oat, winter rye, winter wheat, winter triticale, forage yield, tillering

Influence of Planting Date and Seeding Rate on Winter Wheat Grain Yield and Yield Components

Winter wheat (Triticum aestivum L.) is commonly seeded over a 60-d period in the Midwest depending on crop rotation options, weather, and other farm operations. This study was conducted to determine whether winter wheat seeding rates should be altered depending on planting date and cultivar. Seeding date and planting rate responses of the cultivars, Merrimac and Cardinal, were evaluated at the University of Wisconsin Arlington Research Station during the 1988 to 1991 growing seasons. Eight planting dates ranged from 24 August to 3 November and seeding rates were 14, 28, 42, and 56 seeds/sq ft. Grain yield and yield components were influenced by all variables and specific interactions. Heads per square feet and kernel weight, two primary yield components, decreased as seeding was delayed after 12 September. Maximum grain yield occurred when planting Cardinal on 3 September using 28 seeds/sq ft. Delaying Cardinal planting to late September required a seeding rate of 42 to 56 seeds/sq ft to maximize yield. When planted in September and early October, Cardinal had higher yields than Merrimac due to heavier kernel weight. Changes in yield components allowed plants to adjust to varying conditions as planting was delayed. As grain yield decreased with a planting delay into October, kernel weight and heads per square feet continued to decrease for both cultivars. When planting was delayed past 3 October in 2 of the 4 yr, Merrimac had greater kernel weight, which translated into higher Merrimac grain yields than Cardinal. Grain yields of wheat planted in late October decreased due to yield component response to environment and to stage of plant development when growth ceased. These results can be used to improve establishment and yield of winter wheat, especially when planting at dates that are not always optimum. Research Question Producers aiming for maximum winter wheat grain yields need to begin with successful establishment of the wheat crop in the fall. Optimum planting date and seeding rate are necessary if one wants to attain high yields. This study compared planting date and seeding rate of two cultivars of varying winterhardiness to determine which combination produced maximum grain yields. Literature Summary Previous planting date research has determined that early seeding allows better stand establishment leading to greater yields. Research in Canada established that once planting date is determined, maximum yield for that date will be attained if yield components are managed by adjusting the seeding rate. Cultivars with different degrees of winterhardiness may influence optimum planting date and seeding rate. No published literature was found that examined the interaction of cultivars with planting date and seeding rate for the soft red winter wheat growing region of the Midwest. Study Description This study was conducted for 4 yr, 1988 to 1991, at Arlington, WI, using wheat management practices to maximize grain yield. Date: Eight planting dates in 10-d increments from late August through early November Cultivars: Merrimac-very winterhardy Cardinal-moderately winterhardy Rates: 14, 28, 42, and 56 weeds sq ft Applied Question Are optimum winter wheat seeding rates influenced by planting date and cultivar? Cardinal produced higher yields than Merrimac at all seeding rates when planted prior to 1 October when averaged over all 4 yr of our study (Fig. 1). While cultivars frequently responded differently to planting dates and seeding rates we did not find significant three-way interactions for grain yield. As planting was delayed into October, Merrimac grain yield decreased less rapidly than Cardinal. Merrimac planted in mid-to-late October also provided more consistent yields than Cardinal. We found maximum grain yields could be obtained by seeding Cardinal at 28 to 56 seeds/sq ft up to the third week in September. Growers could save seed costs, however, by using 28 to 42 seeds/sq ft, since the higher rate offered no advantage with early planting dates. When planting date is delayed past 1 October, yields are consistently higher at seeding rates of 42 to 56 seeds/sq ft for both cultivars; however, growers could reduce their risk of crop failure by switching to a more winterhardy cultivar, such as Merrimac. Profitability of winter wheat in the Midwest was the primary objective of our work. We recommend planting higher yielding, less winterhardy cultivars, using lower seeding rates early in the fall for maximum yields. If planting is delayed into October, we recommend that growers switch to more winterhardy cultivars and increase seeding rates. Figure 1Open in figure viewerPowerPoint Effect of planting date and seeding rate on yield of a. Merrimac and b. Cardinal SRWW, averaged over 4 yr, 1988–1991.

Wheat Planting Date Effects on Soil Water Extraction and Grain Yield

AbstractDue to a wide range of irrigated and dryland production systems and highly variable weather, planting date of winter wheat (Triticum aestivum L.) grown in the Southern High Plains varies from August to November. A 2‐yr field study was conducted at Bushland, TX, to evaluate planting date effects on soil water extraction and grain yield. ‘TAM 107’ wheat was planted in late August to simulate a grazed production system, early October to represent an optimum date for grain production, and early November on preirrigated Pullman clay loam soil (fine mixed thermic Torrertic Paleustoll) and grown to maturity without further irrigation. Gravimetric soil water content to 3.6 m depth was determined at the beginning and end of winter dormancy and at anthesis. Water extraction prior to winter dormancy occurred to a depth of 1.8, 0.9, and 0.15 m for the early, normal, and late planting dates, respectively. Depth of water extraction at anthesis was 2.4, 2.4, and 1.2 m for the three dates. The fraction of total preanthesis soil water extraction that occurred during a critical 60‐d period immediately prior to anthesis was 0.22, 0.59, and 0.91 for the early to late planting dates, respectively. Planting in August greatly increased depth and amount of soil water extraction prior to winter dormancy; however, water deficits in the spring contributed to low head density and grain yield. Wheat planted in early October extracted as much soil water as the August planting by anthesis and produced high grain yield. Wheat planted in early November rooted only one‐half as deep, extracted two‐thirds as much water, and yielded two‐thirds as much grain as the October planting date. In conclusion, planting in August as compared with October did not increase soil water extraction at anthesis and grain yield was reduced because the period of major soil water extraction was shifted from spring to fall. Planting in November reduced grain yield because of insufficient rooting to fully extract soil water from below 1.2 m.

Effect of Years and Planting Dates on Fatty Acid Composition of Soybean Genotypes

Soybean [Glycine max (L.) Merr.] genotypes with modified fatty acid composition in the seed oil are being considered for commercial production. The stability of fatty acid composition across a range of environmental conditions will be an important factor for end users of the new soybean oils. The objective of this study was to evaluate the influence of years and planting dates on the fatty acid composition of soybean genotypes with elevated palmitic acid, elevated stearic acid, or reduced linolenic acid. Ten soybean lines with modified fatty acid composition and two common cultivars were grown in 1988, 1989, and 1990 at the Iowa State University Agricultural Engineering and Agronomy Research Center near Ames. Planting dates were 2 May, 16 May, 30 May, and 13 June. For the genotype with elevated palmitic acid, A21, there were significant differences among years, but the maximum difference was only 10 g kg−1. Effects of planting dates were not significantly different for the palmitic acid content of A21. For the genotype with elevated stearic acid, A6, differences among years, planting dates within individual years, and years × planting dates interaction were significant, but the effect of planting dates averaged across years was not significant. Differences among years were significant for the linolenic acid content of most genotypes; however, the maximum difference among years was only 3 g kg−1 for genotypes with an average of <25 g kg−1 linolenic acid. Early planting dates favored lower linolenic acid content, but the maximum difference between 2 May and 13 June for any genotype with <25 g kg−1 linolenic acid was only 4 g kg−1. Average daily high temperature during the seed‐filling period did not consistently explain the differences in fatty acid content among planting dates or years. Our data indicated that different planting dates could not be used as a substitute for years in determining environmental stability of fatty acid composition.

Influence of Planting Date on the Seasonal Abundance of Tobacco Budworms (Lepidoptera: Noctuidae) and Tobacco Aphids (Homoptera: Aphididae) on Georgia Flue-Cured Tobacco

The influence of planting date of flue-cured tobacco, Nicotiana tabacum L., on the seasonal abundance of tobacco budworms, Heliothis virescens (F.), and tobacco aphids, Myzus nicotianae Blackman, was examined in field plots in Georgia during 1987–89. Tobacco aphid population densities (aphids per plant) were influenced by yearly effects; however, tobacco budworm populations (budworms per 10 plants) were similar among the three years. A planting date (PD) effect (late March, mid-April, late April) was observed for tobacco aphids only in 1989, when higher population densities occurred in the late-planted tobacco. Planting date influenced tobacco budworm population densities in two of the three years. Significant differences in tobacco aphid populations were detected between PD's in all three years for the weekly samples in June and July, the period when seasonal aphid densities were the highest. Population peaks were higher in the mid-and late planting dates, except in 1987 when high aphid densities (3000 per plant) occurred only during the early planting date. Weekly differences in tobacco budworm populations also were detected among planting dates on many sampling dates throughout the season in all three years. Tobacco budworms occurred earliest in the early-planted tobacco, but peak densities were highest in the late-planted tobacco. Both tobacco budworm and tobacco aphid populations declined after the plants were topped (terminal floral branch removed) and a fatty alcohol sucker control was applied.

SENESCENCE IN SWEETCORN

Fungi can colonize senescent sweet corn (Zea mays var. rugosa Bonaf.) tissue. Senescence levels of tissues can be rated. Effects of four planting dates on senescence of standard (su, cv. Merit), and supersweet (sh2, cv. Florida Staysweet) corn at fresh market and seed harvest were determined. Stalk senescence was affected by cultivar (sh2 < su) and planting date (earliest was lowest). Shank senescence was affected by cultivar (fresh market < seed harvest) and planting date (lowest for plants of the earliest and latest plantings). Cob senescence was not affected by cultivar, slightly lower at fresh market than seed harvest, and lower for plants of the later than earlier planting dates. In a second experiment senescence was rated during development of sh2 cultivars. Formation of reproductive structures increased senescence rate. Cultivar had little effect on stalk and cob senescence at fresh market harvest. The cv. `Honey'n Pearl' had the lowest shank senescence rating. Delayed senescence should be incorporated in to corn genotypes.

Black Polyethylene Mulch Doubled Yield of Fresh-market Field Tomatoes

Field experiments were conducted to a) maximize total yield of fresh-market field tomato (Lycopersicon esculentum Mill.) cultivars using black polyethylene mulch (BPM), and b) increase fruit size and yield during the last 5 weeks of the production period by reducing the number of synthate sinks per plant through eliminating all flowers that appeared during this period. Unmulched treatments under trickle irrigation and multiple applications of soluble fertilizer yielded an average of 43 t·ha-1 for `Sunny' and `Pik-Rite' over the two planting dates. With BPM, total yield increased by 95% to 84 t·ha-1. Although total yield increases due to BPM over the control were highly significant in both cultivars and over the two planting dates, yield increases were higher for the early than for the optimum planting date. BPM also significantly increased early production of `Pik-Rite' but not `Sunny', and the increase in early production was more pronounced for the optimum than the early planting date. Sink reduction during the last 5 weeks of the growing season had no effect on yield or fruit weight during that period.

EFFECT OF PLANT SPACING AND PLANTING DATE ON YIELD OF ANNUAL STRAWBERRY SYSTEM IN NEW JERSEY

High density strawberry planting systems have increased yield and fruit quality, and allow greater production on small acreage. To adapt the system to New Jersey conditions, replicated plantings of `Chandler', `Tribute', and `Tristar' were established at 3 spacings and two planting dates (9/9, 9/15) in 1989, and two plant spacings and two planting dates (8/14, 9/7) in 1990. Plants were propagated as plugs from runner tips. The plantings were covered with floating row covers (polypropylene) in December, covers were removed in early April at 5% bloom. In 1990, `Chandler' yield increased as density increased, and decreased with later planting date. Fruit quality was very good; saleable % was over 90%. Size ranged from 8 to 21 g., and averaged from 12 to 17 g. for the various treatments. `Tribute' responded similar to `Chandler' but `Tristar' yield at 12″ was not significantly different than 6″, but greater than 9″. Size ranged from 9 to 19 g., and averaged from 10 to 14 g.; saleable % was over 85%. In 1991, 2 spacings (6″, 12″) and 2 planting dates (8/24, 9/7) were tested. The earlier planting date was superior to later; yields were not different between the 6″ and 12″ treatments (yield range: 3.8-5.4 T/A). Size was superior at wider spacing; day-neutral fruit size was small (avg fruit size range: 7.7-11.2g; high range: 10.1-17.4g).

On-farm Experiments as a Diagnostic Method: Constraints to Nitrogen Fertilizer Use on Sorghum in Semi-arid Tropical India

SUMMARYOn-farm diagnostic experiments were used to study constraints to nitrogen fertilizer use, define recommendation domains, and test fertilizer management techniques for two sorghum cropping systems in semi-arid tropical India. In the post-rainy season sorghum cropping system, nitrogen fertilizer use remains negligible because crop response is poor when sorghum is planted after the end of the monsoon, as is traditional. An earlier planting date would introduce high risks. In the dependable rainfall region, nitrogen fertilizer use on hybrid sorghum could be enhanced by tailoring recommendations to broad farmer-designated soil groups, and by educational programmes on the use of complex fertilizers. Additional research on fertilizer efficiencies on shallow Vertisols is needed. Diagnostic experiments proved a useful, relatively rapid and low cost method of research when complemented by farm management and on-station research data.

Stand Establishment of Fluid-drilled Tomato in Rye and Wheat Tillage Systems

Tomatoes (Lycopersicon esculentum Mill.) were grown in conventional tillage (CT), rye (Secale cereale L.) mulch no tillage (RNT), and wheat (Triticum aestivum L.) mulch no tillage (WNT). Either germinated seeds (GS) or raw seeds (RS) were fluid drilled on several dates in 1981 and 1982. Tomato stands in no tillage (NT) generally were equal to or higher than in CT, and stands improved with later plantings in each year. Plant stands were unaffected by GS and RS. Time to 50% emergence (T50) was up to 4 days less in NT than in CT and 2 to 3 days less from GS than RS. Yields with CT were twice as high as those with NT for early planting dates. Yields decreased in CT with successive planting dates to levels equal to NT plantings. Use of GS increased fruit yields as compared to RS, regardless of the planting date.

Agronomic Practices for Production of Ethanol from Sweet Sorghum

Sweet sorghum [Sorghum bicolor (L.) Moench] is a potential alternative feedstock for ethanol production, but its viability will depend upon knowledge of cultural practices which optimize energy yield. Several field studies were conducted in 1987 and 1988 to evaluate the influence of planting date, harvest date, N fertilizers, and plant density on performance of sweet sorghum for ethanol production in the northern Corn Belt. Four sweet sorghum cultivars were planted in late April, early May, mid-May, and late May of 1987 and 1988 at Waseca, MN. Percent fermentable carbohydrate (°Brix or °B) and stalk moisture content were measured at two week intervals from August through October and stalk dry matter and ethanol yields were determined at harvest In mid-October. Dry matter yields ranged from 8 to 10 tons/acre and ethanol yields from 326 to 423 gal/acre with the best cultivar, ‘Keller’. Dry matter yield decreased as planting date was delayed, but °B and stalk moisture were only slightly affected by delayed planting. Fermentable carbohydrate and ethanol yields were about 13% higher at earlier planting dates than at later planting dates. Keller, a late-maturing cultivar, had greater °B and ethanol yields than three other cultivars, but was nearly 100% lodged at harvest. Maximum stalk °B was produced mid- to late September. Neither N fertilizers nor seeding rate significantly affected fermentable carbohydrate or ethanol yield. Early planting dates and late-maturing cultivars with high °B levels are recommended for sweet sorghum, when grown for ethanol in the upper Midwest.

Seed Quality Effect on Corn Performance under Conventional and No-Tillage Systems

In northern regions, no-tillage corn (Zea mays L.) planting often results in reduced and/or delayed seedling emergence and growth. The objective of this research was to evaluate the effects of seed quality on the performance of three commercially available corn hybrids grown with conventional-tillage (CT), no-tillage (NT), and no-tillage with in-row residue removed (NT-R). Field studies were conducted under the three tillage systems with seed lots having high (95–99%), medium (89–98%), and low (84–95%) warm and cold germination test values. Hybrids used were FR20A × FR31, LH74 × LH51, and A632 × LH39. The studies were conducted from 1986 to 1988 on Piano silt loam (fine, mixed, mesic Typic Arguidoll) soils near Arlington and Janesville, WI. There were also early (mid- to late April) and late (mid- to late May) planting dates at Arlington. Increased residue cover with NT and NT-R systems resulted in 2 to 4 °F cooler soil temperatures at planting compared to CT, which reduced average percentage corn emergence by 3%, delayed emergence by 2 to 5 d, reduced vegetative dry weight at 45 d after planting by 30 to 60%, delayed silking 5 to 7 d, and increased harvest grain moisture 1 to 5%. Average grain yields were also reduced by 9% under NT compared to CT. Compared to high quality seed, medium and/or low seed quality caused 4 to 6% lower emergence, delayed emergence less than 1 d, reduced vegetative dry weight by 10 to 15%, extended days to silking by 1 to 2 d, increased grain moisture about 1%, and decreased average grain yield by 4% (despite thinning to constant final stands). Seed quality effects were usually smaller than tillage system effects, and tillage system by seed quality interactions were infrequent. Special concern about seed quality under NT is unwarranted, but to optimize probability for high yields growers should plant high quality seed regardless of the tillage system used.

CULTURAL METHODS AFFECTING YIELD OF EDIBLE DRY BEANS

The effects of planting date and plant density on total and marketable yield were examined for the edible dry beans `Aurora' and `Fleetwood', erect type I geneotype cultivars, over three years. For `Fleetwood' alone, fertilizer levels and application of a spray-on-soil polymer mulching material were examined for effects on yield. The mulching material was degraded by rain prior to canopy closure but patches were present at harvest. Using continous recording thermometers, temperatures over two week periods following sowing of `Fleetwood', from 23 cm below the surface of mulched and bare soil were converted to soil degree days (SDD). `Fleetwood' generally had higher yields than `Aurora'. Earlier planting improved yields. In one of three years increasing plant density increased yields. Increased fertilization did not affect yield. Application of mulch did not affect yield. However, spray-on-mulch did increase SDD after the earliest planting date. Cultural systems for existing production, or potential production areas, must be developed for the conditions of each location.

The Effect of Different Planting Dates on the Infestation of Soybean by Heterodera glycines Race 5

The effects of different planting dates on infestation of susceptible soybean cvs. Essex and Lee by Heterodera glycines were investigated during three growing seasons. Early planting dates of susceptible soybean cvs. at lower temperatures resulted in smaller nodules, lower nematode populations and field infestations, lower soybean cyst nematode (SCN) disease ratings, taller plants, and higher yields. SCN induced more nodules on soybean roots at 14 May plantings date. The development of SCN race 5 in the field was associated closely with soil temperature. The infestation of susceptible soybean cvs. at early planting dates by H. glycines greatly affected the agronomic performance of these cvs. in the field. Susceptible soybean cvs grown in infested soil with SCN race 5 planted earlier than the recommended planting dates escaped severe infestation of SCN in the field.

Rapid Isolation and Measurement of Adenosine Triphosphate Levels in Corn Embryos Germinated at Suboptimal Temperatures

The trend towards earlier planting dates and conservation tillage systems in corn (Zea mays L.) production has prompted interest in accurate methods for predicting cold tolerance in germinating seedlings. Measurement of nucleotide phosphate levels in germinating seed has been proposed as one such method, but has proven to be a tedious procedure to apply to plant materials. A nucleotide extraction technique was combined with high performance liquid chromatography (HPLC) and applied to the measurement of adenosine triphosphate (ATP) in germinating corn embryos. Embryo ATP concentrations were determined for seed lots of two corn hybrids imbibed over a 96‐h period at two temperatures, 10 and 20 °C. The lower temperature reduced ATP levels and accumulation rates for both cultivars. Differences in the embryo ATP concentrations of the respective hybrids were apparent after 32 h of imbibition at 10 °C. Differences in the ATP accumulation rate of those embryos were detectable 4 to 16 h into the germination process. Significantly lower quantities of ATP in one hybrid (Dekalb‐Pfizer XL 72B) germinated at 10 °C for 64 h were associated with a corresponding reduction in cold‐test germination percentage of that seed. Measurement of embryo ATP levels for six additional hybrid seed lots after 64 h of germination at 10 °C revealed significant variations in ATP concentration. Correlation of embryo ATP levels and cold‐test germination percentages with the field performance of these hybrids indicated that embryo ATP levels were a more reliable predictor of cold tolerance than the cold germination test.