June Planting Research Articles

NC 98-608: MANAGING THE POTENTIAL NEW SWEETPOTATO (Ipomea batatas) CLONE RELEASE

The goal of this research was to determine the effects of in-row spacing and planting time on yield and root grade of NC 98-608 over time. Two plantings were made in two grower locations (four total). An early planting was made 19 and 25 May and a late planting 19 and 24 June. NC 98-608 was evaluated at the following in-row spacings; 23, 31, 38, and 46 cm. `Beauregard' spaced at 23 cm in-row and was used as the standard comparison. Roots were harvested and graded into canner, number one, jumbo and cull grades 90, 105, and 120 days after planting for each of the planting dates and locations. Each grade was weighed. An early planting in late May resulted in roots reaching the highest percentage grade of U.S. number one roots as early as 100 days after planting, while the late planting in June resulted in roots never reaching their full number one yield potential in some cases. For an early harvest after planting (90 days after planting) the 38 cm in-row spacing produced the most marketable number one yields compared with the 23, 31, and 46 cm in-row spacings. For a later harvest time after planting (105 days or later), it appeared as though the 31 cm in-row spacing was the most economical spacing to use. Roots from the early plantings (late May) and finer textured soils appeared to have shorter roots than roots harvested from later plantings (after 15 June) or coarser textured soil. Root shape and yield was more uniform with NC 98-608 than with the Beauregard clone. With yields comparable to Beauregard, the NC 98-608 clone provides an excellent opportunity to produce a quality sweetpotato with consistent shape.

Seeding Practices and Cultivar Maturity Effects on Simulated Dryland Grain Sorghum Yield

Typical planting recommendations for dryland grain sorghum [Sorghum bicolor (L.) Moench] in the southern High Plains are to delay until soil water is adequate for crop establishment, but no population or cultivar maturity class are specified. Our objectives were to use the SORKAM simulation model, long‐term (1958–1998) weather records at Bushland, TX, and known Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustolls) properties to identify an optimum planting date, population, row spacing, and cultivar maturity combination to maximize dryland grain sorghum yield. We simulated sorghum grain yields for combinations of planting dates (15 May, 5 June, and 25 June), populations (3, 6, and 12 plants m−2), row spacings (0.38 and 0.76 m), and cultivar maturity class (early, medium, and late). SORKAM consistently (r 2 = 0.69, RMSE = 792 kg ha−1) simulated grain yields that averaged about 5% more than measured values and correctly simulated row width and population effects on yield. Simulated grain yields increased with narrow row‐spacing ∼9%, independent of planting date or cultivar. Increasing plant population significantly decreased panicle seed number, seed mass, and plant tillers; however, the simulated grain yield was unchanged (3996–4106 kg ha−1) by plant populations. Mean simulated grain yields were greatest for the 5 June planting dates with early and medium maturity cultivars that avoided late summer heat or water deficit stresses and matured before freezing weather. Our results show early or medium maturity cultivars, planted 5 June, in 0.38‐m row widths, using 3 or 6 plants m−2, achieve the greatest dryland grain yield on a southern High Plains clay loam soil.

Soybean Development in the Midsouthern USA Related to Date of Planting and Maturity Classification

Soybean (Glycine max) is planted from late March through June in the midsouthern USA. Different developmental patterns that result from this range in planting dates will affect management decisions. Irrigated field studies were conducted at Stoneville, MS (33° 26′N) from 1979 through 2003 to determine effect of late March through June planting dates on developmental patterns of maturity group (MG) IV through MG VI soybean. In all plantings, time from planting to beginning bloom (R1) increased as MG increased from IV to VI. Time from R1 to full seed (R6; pod cavity filled) was sometimes but not always different among the MGs, and differences were always ≤ 7 days. The major difference in the length of growing season among cultivars of different MGs occured before reproductive development began regardless of planting date. Thus, performance of soybean cultivars of disparate MGs should not be affected by differences in time between stages of reproductive development, but rather by when the stages occur.

Effects of integrating host plant resistance with time of planting or fungicides on anthracnose and grain mould and yield of sorghum (Sorghum bicolor) in the Nigerian northern Guinea Savanna

Two field trials were conducted in the 1999 and 2000 cropping seasons to determine the effect of planting date and host plant resistance on grain mould and anthracnose, and host plant resistance with fungicides on anthracnose of sorghum in the Nigerian northern Guinea Savanna. Three sorghum varieties were used [SAMSORG 40 (ICSV 111), SAMSORG 4 (KSV 4) (both early maturing and susceptible to anthracnose) and SAMSORG 14 (KSV 8) (medium maturing and resistant to anthracnose)]. Results show that early planting in June and the first 2 weeks of July predisposed susceptible varieties to high level of anthracnose while planting in June predisposed SAMSORG 40 and SAMSORG 4 to high levels of grain mould but gave highest grain yield for the three varieties. The resistant variety SAMSORG 14 was resistant to both anthracnose and grain mould irrespective of planting date. Foliar application with benomyl controlled anthracnose and gave highest yields when combined with seed treatment using metalaxyl+carboxin+furathiocarb (MCF). However, seed treatment alone with MCF did not control anthracnose.

Yield and Relationships among Head Traits in Cabbage as Influenced by Planting Date and Cultivar. I. Fresh Market

Yield and relationships among head traits were recorded in order to better understand the effects of planting date and cultivar selection on crop quality characteristics and to help increase the efficiency of cultivar development, evaluation, and selection. A total of seven cultivars of fresh market-type cabbage (Brassica oleracea L., Capitata Group) were planted in May and June of 1999 and 2000 at the OARDC Vegetable Crops Research Branch in Fremont, Ohio. Total and marketable yield, head traits (e.g., size, weight, density), and core dimensions were recorded at harvest. Main effects of year (Y), planting date (PD), and cultivar (C) and the Y × C interaction significantly affected seven to 10 of 10 head and core traits. However, the PD × C interaction was significant for head density, the ratio of head polar and equatorial diameter, and core base width. The Y × PD interaction was significant for six of 10 head and core traits. May planting tended to result in greater yield and larger, heavier heads with greater polar/equatorial diameter values relative to June planting. However, head density was unaffected by planting date. The number of head and core traits affected by planting date differed among cultivars. For example, six of 10 head and core traits were significantly affected by planting date in `Cheers' and `DPSX315' while one trait was affected by planting date in `SuperElite Hybrid'. The weight of numerous, individual, market-ready, trimmed heads showed a strong (avg. R2 value = 0.92) quadratic relationship to average head diameter. These data suggest that large-scale germplasm evaluations may benefit by including multiple plantings, as head weight, volume, diameter, and shape were affected by planting date, possibly due to variation in temperature and rainfall patterns. The data also suggest that routine measurement of numerous head traits in the same evaluations may be unnecessary, as selected traits (e.g., diameter and weight, head volume, and core volume) were strongly related.

Optimum Planting Procedures for Eastern Gamagrass

Eastern gamagrass (Tripsacum dactyloides L.) is a warm‐season, perennial bunch grass with great potential for use in grazing, cut forage, and conservation systems. Current recommendations for planting eastern gamagrass during the winter (November to February) are suitable for many areas but are inadequate in locales were the ground is frozen during most of this period. The objectives of this study were to determine the best combinations of planting date, planting depth, and seed stratification for eastern gamagrass in the northern range of its adaptation. Unstratified and stratified gamagrass seed was planted in mid‐August, late October–early November, mid‐April, mid‐May, and mid‐June at 2.5‐ and 5.0‐cm planting depths over two growing seasons. Planting in the late summer and fall resulted in better stand establishment than planting in the spring and early summer. The net seedling survival from plantings in April and May was 39 and 48% less than from summer and fall plantings of unstratified seed in 1999–2000 and 2000–2001, respectively. Seed stratification was beneficial to April plantings in only one year of the study and did not improve May or June plantings. At most planting dates, depth had little influence on final stand. Full stands contained at least one plant per 25 cm of row. Plantings producing stands above this level were the August, November, and June plantings in both years and the April planting of stratified seed in the first study year. While the June plantings resulted in adequate final stand numbers, stand establishment was delayed for more than 10 mo because most of the plants did not emerge until the following spring.

Planting Date and Hybrid Influence on Corn Forage Yield and Quality

Producers believe that corn (Zea mays L.) forage can be planted at later dates than corn grain because forage harvest does not have to wait until the grain matures fully. The objectives of this study were to determine relationships between planting date and corn forage yield and quality and to determine optimum planting dates of corn forage for the state of Wisconsin. Full‐ and shorter‐season hybrids were planted on six dates at six locations in Wisconsin during 1998 and 1999. Few significant hybrid × planting date interactions or hybrid differences were observed. The optimum planting dates for dry matter yield and quality for southern, central, and northern Wisconsin were 10 May, 27 April, and 8 May, respectively. Corn forage yields remained at 95% of maximum yields when corn was planted in late May for all zones. In all zones, early June plantings exhibited an accelerated rate of yield decline of 0.2 Mg ha−1 d−1 delay in planting. Corn forage quality decreased progressively as planting dates progressed into June. The optimum planting date for milk yield ha−1 was 2 May in southern and central zones and late April in the northern zone. As planting was delayed past mid‐May, rates of quality decline were more severe in central and northern zones compared with the southern zone. Therefore, planting of corn forage should occur between late April and mid‐May for all production zones in Wisconsin, but planting could occur into late May in the southern production zone because milk yield ha−1 declined by only 8%.

Dairy Diet Phosphorus Effects on Phosphorus Losses in Runoff from Land‐Applied Manure

Phosphorus losses from land‐applied manure can contribute to nonpoint source pollution of surface waters. Dietary P forms and levels influence P concentrations in animal manures and may affect P losses from land‐applied manure. The objective of this study was to determine the effects of dairy diet P concentration on P losses in runoff from land‐applied manure. Dairy manures from two dietary P levels were applied (24 May 1999) at 56 wet Mg ha−1 to a silt loam soil, to provide 40 and 108 kg P ha−1, respectively. The high P diet manure was also applied at 21 wet Mg ha−1 (40 kg P ha−1) to provide a P rate equivalent to the low P diet manure. Plots were subjected to simulated rainfall (75 mm h−1) just prior to corn (Zea mays L.) planting in June and again after harvest in October 1999. Runoff was analyzed for dissolved reactive P (DRP), bioavailable P (BAP), total P (TP), and sediment concentration. Natural runoff from the same plots was collected from November 1999 through July 2000 and analyzed for DRP. At equivalent manure rates, DRP concentration in June runoff from the high P diet manure was ≈10 times higher (2.84 vs. 0.30 mg L−1) than the low P diet manure, and four times higher (1.18 vs. 0.30 mg L−1) when applied at equivalent P rates. Phosphorus concentrations in October runoff and November to July natural runoff were lower (0.02 to 1.69 mg L−1), but treatment effects were the same as for the June runoff. These results show that excessive addition of inorganic P to dairy diets increases the potential for P loss in runoff from land‐applied manure, even at the same P application rate. Diet P effects on potential losses in runoff from land‐applied manure should be considered in P‐indexing and nutrient management planning.

Dairy Diet Phosphorus Effects on Phosphorus Losses in Runoff from Land-Applied Manure

Phosphorus losses from land-applied manure can contribute to nonpoint source pollution of surface waters. Dietary P forms and levels influence P concentrations in animal manures and may affect P losses from land-applied manure. The objective of this study was to determine the effects of dairy diet P concentration on P losses in runoff from land-applied manure. Dairy manures from two dietary P levels were applied (24 May 1999) at 56 wet Mg ha−1 to a silt loam soil, to provide 40 and 108 kg P ha−1, respectively. The high P diet manure was also applied at 21 wet Mg ha−1 (40 kg P ha−1) to provide a P rate equivalent to the low P diet manure. Plots were subjected to simulated rainfall (75 mm h−1) just prior to corn (Zea mays L.) planting in June and again after harvest in October 1999. Runoff was analyzed for dissolved reactive P (DRP), bioavailable P (BAP), total P (TP), and sediment concentration. Natural runoff from the same plots was collected from November 1999 through July 2000 and analyzed for DRP. At equivalent manure rates, DRP concentration in June runoff from the high P diet manure was ≈10 times higher (2.84 vs. 0.30 mg L−1) than the low P diet manure, and four times higher (1.18 vs. 0.30 mg L−1) when applied at equivalent P rates. Phosphorus concentrations in October runoff and November to July natural runoff were lower (0.02 to 1.69 mg L−1), but treatment effects were the same as for the June runoff. These results show that excessive addition of inorganic P to dairy diets increases the potential for P loss in runoff from land-applied manure, even at the same P application rate. Diet P effects on potential losses in runoff from land-applied manure should be considered in P-indexing and nutrient management planning.

Physiological parameters and grain yield as influenced by time of transplanting and rice (Oryzasativa) hybrids

A field experiment comprising 4 dates of transplanting (15, 25 June and 5, 25 July) in conjunction with 4 genotypes (3 hybrids : OR1 161 PMS2AlIR31802, PMSlOA/PR106 and 1 inbred variety HKR 126) was conducted during rainy season of 1993 and 1994. Crop-growth rate (CGR) prior to panicle-initiation (PI) stage was higher in July transplanting, whereas it increased significantly in 25 June planting during post-PI stage through flowering period. Leaf-area duration (LAD) during pre-PI stage was the longest in the most delayed planting, but 25 June planting excelled over other dates during flowering period of crop growth. Leaf-area ratio (LAR) was the highest in June-planted crop at all the time intervals. Panicles/m2, grain and straw yields were higher in 25 June-planted crop, followed by 5 July. Spikelet sterility was maximum in 25 July and minimum in 25 June-transplanted crop. Hybrid OR1 161 (PHB 71) exhibited superiority to other genotypes in CGR, LAD, grain yield and straw yield. Spikelet sterility (%) was lowest in OR1 161, followed by HKR 126.

Management of Corn Earworm and Fall Armyworm (Lepidoptera: Noctuidae) Injury on a Sweet Corn Hybrid Expressing a cryIA(b) Gene

Research was conducted to evaluate transgenic sweet corn containing a modified cryIA (b) gene from Bacillus thuringiensis (Bt) and a minimal number of insecticide applications for management of injury to ears by corn earworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda (J. E. Smith). GH-0937 (Bt+), Bonus (Bt-), and Silver Queen (Bt-) sweet corn hybrids were planted 15 April, 1 May, 15 May, 1 June, and 15 June 1997 to provide different intensities of insect pressure as populations increased during the season. During ear development, methomyl was applied in 0, 1, 3, or 5 applications beginning when 50% of the plants were silking. GH-0937 exhibited a high level of resistance to leaf feeding in the whorl stage by fall armyworm and to ear injury by the corn earworm and fall armyworm. With extreme insect pressure on plants for the 15 June planting, as evidenced by the extensive damage to Bonus and Silver Queen in the whorl stage, injury to ears of GH-0937 averaged only 7.9 cm 2 of kernel damage when no insecticide was applied, and was reduced to an average of only 1.7 cm 2 of kernel damage with 5 applications of methomyl. In this same test, Silver Queen and Bonus averaged 323 and 168 cm 2 of kernel damage, respectively, with no insecticide applications, and 172 and 50 cm 2 , respectively, with 5 applications of methomyl. Injury to ears on GH-0937 was not eliminated, but was minimal and confined to a few kernels at the ear tip. Most of the observed injury was from feeding by nitidulid beetles, or to an occasional large fall armyworm larva that migrated from a susceptible plant to an untreated ear of GH-0937 where it fed before dying. Bt sweet corn offers an excellent opportunity to develop more environmentally compatible approaches for sweet corn production.

Does the Systemic Insecticide Imidacloprid (Gaucho) Have a Direct Effect on Yield of Grain Sorghum?

Gaucho1 (imidacloprid; l-[(6-chloro-3-pyridinyl)methyl]-N-nitro-2-imidazolidinimine) is a seed treatment insecticide widely used on sorghum [Sorghum bicolor (L.) Moench] to control a number of pests, including greenbugs [Schizaphis graminum (Rondani)], chinch bugs [Blissus leucopterus leucopterus (Say)], and wireworms (Limonius sp.). A series of tests was conducted at five locations in Kansas during 1996 and 1997 and three locations during 1998 to determine whether a yield response results even in the absence of pests when Gaucho is used as a seed treatment on grain sorghum. Results varied. Gaucho improved yields at Hesston, especially in the June plantings but some hybrids benefited more than others. These differences may have been due to chinch bugs that were observed in the plots and were known to be troublesome in the area. Because their numbers were low, other factors may have played a role. At the other locations and in the absence of chinch bugs, Gaucho had less of an influence on yields. At Garden City, where some greenbugs developed, Gaucho provided early-season control, but infestations were too light to influence yields. At Hays, Gaucho treatments appeared to have some influence on the numbers of corn earworms [Helicoverpa zea (Boddie)] in sorghum heads in one planting, although yield differences were not significant. Overall, this study found no consistent yield increases in fields treated with Gaucho in the absence of observable pest activity. Research Question Gaucho is the trade name for imidacloprid, a systemic insecticide commonly used as a seed treatment on sorghum for control of chinch bugs, greenbugs, and other insects. Its ability to control these insects and protect sorghum yield potential is well documented. However, the effects of Gaucho on sorghum growth, development, and yield in the absence of noticeable insect populations are less well understood. Growers and others using this product have suggested that a yield increase can occur in the absence of insect attack. We were interested in determining whether this is true and under what conditions it would occur. Literature Summary The insect controlling effects of imidacloprid are well documented. The insecticide is registered for control of such pests as greenbug, chinch bug, and wireworms. Other systemic insecticides such as disulfoton and carbofuran have been shown to have direct effects on plant growth and crop yields. For example, yields of peanut, tobacco, and sorghum were increased in soil treated with disulfoton and yields of tobacco, corn silage, corn grain, rice, and grain sorghum were increased with carbofuran soil treatments. However, other studies have shown no yield response to carbofuran by corn or to disulfoton or phorate by soybeans. Study Description Tests were conducted at five locations representing various soil types and agronomic practices in Kansas in 1996 and 1997 and three locations in 1998. Treated and untreated seed of five sorghum hybrids were obtained. Each treated lot was treated with Gaucho at a rate of 4oz. ai/cwt. Additional hybrids were evaluated at one location in 1996 and 1997. Plant stands were recorded at the 2-leaf stage of development. Head counts were made approximately 3 wk after the bloom stage. Plots were harvested with a modified two-row Gleaner combine, and yields and test weights were determined. Plots were examined at various intervals for the presence of insects. When infestations occurred, the numbers per plant were determined by examining several plants in each plot. Applied Questions Were insect populations present in these tests? Small numbers of chinch bugs were detected at Hesston and greenbugs were detected at Garden City but in general insect activity was not detected. When insects were present, did the insecticide treatments have any effect? Imidacloprid gave good control of greenbugs early in the season and caused about a 50% reduction in greenbug numbers late in the season at Garden City. At Hesston, chinch bugs were present but numbers were too low to quantify. Did the insecticide treated plots have a higher yield in the absence of insect attack? In general, no consistent yield increase occurred in Gaucho treated sorghum at five locations in Kansas. The exception was at Hesston, where significant increases were noted with some hybrids in both 1996 and 1997. Recommendation Our study suggests that yield improvement following use of Gaucho in fields with no noticeable pest activity is overrated. A consistent yield response was only observed at one location, which frequently experiences problems with chinch bugs. Low insect numbers were observed in the plots at this location. Some hybrids respond to the Gaucho treatment more than others.

Use of resistant and susceptible potato cultivars in the trap cropping of potato cyst nematodes, Globodera pallida and G. rostochiensis

SummaryThe effects of planting date and growing period of potato cultivars on their efficiency as trap crops for potato cyst nematodes (PCN) were studied. Plots were planted with susceptible or resistant cultivars in April, June and August and these were grown for 5, 6 or 7 wk before removal of the plants by hand lifting. Crops planted in June provided the best overall reductions in PCN population density of up to 95%, with cv. Santé significantly more effective than the other cultivars. Population reductions from the August planting were only slightly less than from planting in June but the tuber yields obtained were much greater: Maris Piper and Maris Bard produced 16.4 and 21.4 t ha‐1 respectively, with 37% and 43% respectively, of a size useful for canning (i.e. between 20 and 40 mm diameter).

Long-Term Study of Planting Date Effects on Seed Yield in Soybean

Planting date in relation to subsequent crop development and yield are important determinants in realizing crop yield potential. This study was conducted to determine optimum planting dates for Oklahoma adapted maturity groups of soybean [Glycine max (L.) Merr.]. Effects of planting date on yield were investigated at Bixby, OK, in tbe Uniform Soybean Tests for Southern States. Field experiments were conducted from 1958 through 1994. Planting dates across years ranged between 10 May and 1 July, and were assigned to 5-d, planting intervals. Maturity groups IV, V, and VI were evaluated. Soil type was a Wynona silty clay loam (fine-silty, mixed, thermic Cumulic Haplaquoll). Significant interaction occurred between maturity group and planting interval for yield. Highest average yields produced by maturity group IV (2248 lb/acre) occurred with 9 to 18 May and 8 to 22 June planting intervals. Lowest average yields for maturity group IV (1524 lb/acre) occurred with 19 May to 7 June planting intervals. Highest average yields for maturity group V (2573 lb/acre) occurred with 14 to 18 May and 13 to 22 June planting intervals, and lowest average yields (1950 lb/acre) with 19 May to 12 June planting intervals. Maturity group VI produced highest average yields (2501 lb/acre) with 14 to 18 May, 3 to 7 June, and 13 to 22 June planting intervals. Maturity group VI yields for all other planting intervals averaged 2073 lb/acre. During the range of planting dates available from early May to early July, for maturity groups IV, V, and VI, definite optimum planting dates occur for highest yields. Knowledge of optimum planting dates can be one crop management tool applied to enhance crop productivity, facilitate cropping patterns, and better utilize environmental conditions. Problem Determining optimum planting dates for maximum seed yield is fundamental for successful crop production. This study was conducted to identify optimum planting dates based on seed yield for adapted maturity groups. Background Growers have a relatively long period between early May and early July for planting soybean in Oklahoma. Different maturity groups may produce different seed yields and change in relative rank for various dates of planting. This requires evaluation of maturity groups within planting dates and planting dates within maturity groups rather than considering either maturity group or planting date alone. Identification of optimum planting dates for different maturity groups would enable minimizing the effects that temperature, water stress and photoperiod may have on seed yield. Study Description This study was conducted from 1958 through 1994 on a Wynona silty clay loam at the Oklahoma Vegetable Research Station in Bixby, in the Uniform Soybean Tests for Southern States. Genotypes used each year were dependent upon entries in the Uniform Soybean Tests. Maturity groups IV, V, and VI were included. Maturity group IV contained both determinate and indeterminate genotypes. Maturity groups V and VI consisted of only determinate genotypes. All maturity groups were planted on the same date in a particular year, but planting dates changed from year to year. Planting dates ranged between 10 May and 1 July across the years. Planting periods between 9 May and 2 July were assigned to groups of 5-d intervals. Experiments were conducted under normal dryland conditions using cultural practices considered standard for the region. Seed yield was measured on each entry for the planting date in each year. Applied Questions Using genotypes representing maturity groups grown in Oklahoma, when are optimum planting dates for each maturity group? For each maturity group in this study, mid-May and mid- to late June plantings produced highest average seed yields. Lowest yields obtained for all maturity groups generally occurred for plantings between 19 May and 7 June. An exception was maturity group VI producing a high yield at the 3 to 7 June planting interval (Fig. 1). Figure 1Open in figure viewerPowerPoint Mean seed yield of each maturity group for each planting interval at Bixby, OK, from 1958 through 1994. What maturity groups produced highest yields for the various planting dates? For several planting intervals, maturity groups V and VI tended to produce higher seed yields than maturity group IV, but statistical significance did not exist at all planting intervals. Maturity group VI genotypes produced better seed yields than maturity group IV when planted in very late May or early June.

Risk Analysis of Planting Date, Seeding Rate, and Grain Sorghum Hybrid Maturity in Kansas Using Simulated Yields

Many variables influence yields of grain sorghum [Sorghum bicolor (L.) Moench] and make it difficult to provide appropriate recommendations to managers concerning planting dates, seeding rates, and hybrid maturity classes. General recommendations in extension publications provide a wide range of possible planting dates and seeding rates and usually suggest planting the latest maturing hybrid within the limitations of projected moisture availability and average length of growing season. Most research related to these issues focuses on just one variable, while holding others constant. This study used simulated grain sorghum yields to provide an economic risk analysis of planting date, seeding rate, and hybrid maturity for grain sorghum production in Kansas. The results showed that optimal planting dates, seeding rates, and maturity classes vary by location and risk preference. In general, the results indicate that extremely risk-averse managers would choose somewhat later planting dates, earlier maturing hybrids, and lower seeding rates than less risk-averse or risk-preferring managers.

Grain Amaranth Seeding Dates in the Northern Great Plains

AbstractAn understanding of crop response to planting date is essential when evaluating a potential new crop. A field study was designed to determine the optimum range of planting dates for dryland grain amaranth (Amaranthus cruentus L. and A. hypochondriacus L. ✕ A. hybridus L.) in the Northern Great Plains. Four grain amaranth cultivars, diverse for plant height and branching, were evaluated over four consecutive years from 1989 to 1992 at Prosper (46°58′ N, 97°4′ W, elevation 220 m) in North Dakota. Soil types at the test site are a complex of Perella (fine‐silty, mixed, superactive, frigid Typic Endoaquolls) and Beardon (fine‐silty, mixed, superactive, frigid Aeric Calciaquolls). Four or five planting dates were selected, ranging from 1 May to 1 July at approximately 15‐d intervals. Year‐to‐year differences in weather influenced the response of amaranth to planting date for grain yield, days to anthesis, harvest index, plant height, final plant population, and lodging. Plants sown in mid‐June produced the greatest grain yield in 1989 and 1990, when near‐ or above‐average temperatures occurred throughout most of the growing season. Seedling survival was greater with later planting dates in all years except 1989, when excellent stands were achieved with all planting dates. Greatest yields in 1992, an unusually cool year, were produced with May planting dates; in that year, most plants sown in mid‐June did not mature before first frost. Material planted on 1 July failed to mature in both 1991 and 1992. In years with near‐ or above‐average temperatures, the mid‐June planting date was best for maximizing both stand establishment and grain yield. Given the uncertainty in predicting weather conditions, planting in early June in the Northern Great Plains should achieve good stands and produce high grain yields, while minimizing the risk of yield loss associated with cool condition.

Early‐Maturing Soybean Cropping System: III. Protein and Oil Contents and Oil Composition

AbstractExpanding production of early‐maturing soybean [Glycine max (L.) Merrill] cultivars in the southeastern USA has exposed such cultivars to a wide range of environmental conditions during seedfill. Temperatures during this growth stage influence levels of specific fatty acids, particularly of the unsaturated fatty acids. Our objective was to evaluate the grain quality responses of early‐maturing cultivars to the wide range of planting dates in the southeastern USA. Protein and oil contents, along with fatty acid profiles, were assessed for cultivars from Maturity Group (MG) 00 through IV using late April, mid‐May, early June, and late June planting dates on a well‐drained Maury silt loam (fine, mixed, mesic Typic Paleudalf) in 1990 through 1993. Across years and cultivars, delayed planting increased protein content and linolenic acid levels and reduced oil content and oleic acid levels, but had little or no influence on palmitic, stearic, or linoleic acid levels. The higher seed‐fill temperatures associated with early planting were strongly correlated with increased oil content and oleic acid levels and reduced linolenic acid levels. Increasing seed‐fill temperatures were closely associated with reduced linolenic acid levels for all six cultivars. However, the oleic acid response to seed‐fill temperatures strongly depended on cultivar maturity. Oleic acid levels of early‐maturing cultivars were much more sensitive to seed‐fill temperatures than were those of later maturing cultivars. While overall effects of environment on grain quality characteristics may be relatively small, perhaps the quality of new low linolenic acid cultivars could be amplified through culture under the warmer conditions of the southeastern USA.

Early‐Maturing Soybean Cropping System: I. Yield Responses to Planting Date

AbstractAn early‐planted, early‐maturing soybean [Glycine max (L.) Merrill] cropping system has been quite successful across the southeastern USA. This cropping system was intended to use early planting to improve yield by avoiding late season drought stress. However, producers in this region use planting dates ranging from late April through late June. Our objective was to characterize the yield response of early‐maturing cultivars to environmental conditions over a range of planting dates. Field studies were conducted on a well‐drained Maury silt loam (fine, mixed, mesic Typic Paleudalf) in 1990 through 1993 using cultivars from Maturity Group (MG) 00 through IV planted in late April, mid‐May, early June, and late June each year. Modest moisture stress was observed over the years tested; however, temperatures during soybean growth stages depended strongly on planting dates. When averaged across years and cultivars, yields were similar for the first three planting dates. Best overall yields were obtained using the MG IV cultivar for late April and mid‐May planting; however, its advantage over MG II and III cultivars diminished for the early June planting date and disappeared for the late June planting date. Early‐maturing cultivars (MG 00 to I) were less likely to achieve competitive yield levels. Lower yields of early‐maturing cultivars for the late April planting date were associated with low temperatures during vegetative growth and with high temperatures during seedfill. In the absence of pronounced moisture stress, low or high temperatures may become the key environmental factors limiting yield. Early planting, a centerpiece of previous successful early‐maturing soybean cropping systems in the southeastern USA, appears to be less important under more favorable moisture conditions.

Transplanted maize (Zea mays) for grain production in southern England. II. Effects of planting date, transplant age at planting and cultivar on growth, development and harvest index

Maize seedlings (cultivars Bastion, Ace, Anko and Mirna) were raised for 15, 30 or 45 days in a glasshouse and planted in the field between early May and mid-June in 1989 and 1990, at 10 plants/m2. Samples of transplants and direct-seeded crops of the same cultivars were taken at regular intervals throughout the growing season for growth analyses. In both years, the 15-day-old transplants established more rapidly in the field than older transplants, and the patterns of leaf production of these young transplants were similar to those of direct-seeded maize. Transplants flowered earlier than direct-seeded maize from the same planting date. At most harvests, transplants showed significantly higher dry weights than their direct-seeded counterparts, and May-planted maize had significantly higher dry weights than June-planted crops, while cultivar effects were small. Final biomass yields were consistently higher in 1989 (17 t/ha) than in 1990 (11 t/ha). In both seasons, particularly in 1990, there was a trend for a lower harvest index in direct-seeded maize which reflected its immaturity at final harvest. The lowest harvest index (0·07) in 1990 was recorded for direct-seeded maize of the late cultivar, Mirna (June planting), the highest harvest index (0·65) for 30-day-old Mirna transplants (May-planted). A comparison of the experienced effective temperature sums during the vegetative, reproductive and grain-filling phases suggested that the transplant nursery period provides an advancement in thermal time which can affect grain-filling and crop maturity. Year to year variation in climate seems to be of primary importance for yield advantages of transplanted over direct-seeded maize.

Transplanted maize (Zea mays) for grain production in southern England. I. Effects of planting date, transplant age at planting and cultivar on grain yield

Agroclimatic conditions in the UK are not ideally suited to maize (Zea mays L.) as a grain crop. An alternative growing technique to direct-seeded maize was investigated at Reading University over three growing seasons, using four cultivars (Bastion, Ace, Anko and Mirna) of different FAO maturity ratings. In the main trials conducted in 1989 and 1990, seedlings were raised for 15–45 days in a glasshouse and planted in the field between early May and mid-June, at 10 plants/m2. On each planting date, maize kernels of the same cultivars were also sown in the field. At the end of each growing season, transplanted and direct-seeded crops were assessed for grain maturity and grain yield components. Averaged over year and cultivar, transplants matured significantly earlier than direct-seeded maize and tended to give higher grain yields. Their grain dry weights (86% DM) averaged 7·0 t/ha in a preliminary study in 1988, 9·0 t/ha in 1989 and 6·1 t/ha in 1990, whereas those of direct-seeded maize averaged 4·0, 8·0 and 3·0 t/ha, respectively. The highest grain weights resulted from May plantings using 15-day-old seedlings of the late cv. Mirna, and from June plantings using 30-day-old seedlings. Yield benefits from transplanting were not significant in 1989, suggesting that in a very warm season transplants may not necessarily outyield direct-seeded crops. Differences in grain weight between transplanted and direct-seeded maize are discussed with respect to grain moisture content, 1000-grain weight, ear length, and number of grains and grain rows per ear; and applications of maize transplanting for cropping systems are outlined. It is concluded that suitable combinations of cultivar, transplant age at planting and planting date can meet the thermal time requirement for a grain harvest in southern England.