Mesic Typic Haplaquoll Research Articles

Corn Hybrid Responses to Reconstructed Mine Soils in Western Illinois

AbstractFederal law requires that surface‐mined prime farmland be reclaimed and restored to productivity for row crops equivalent to that present before mining (Surface Mining Control and Reclamation Act, 1977. Public Law 95‐87. U.S. Code Vol. 30, Sect. 1265). Success of reclamation of such cropland shall be determined on the basis of crop production from the mined area compared to an approved reference area or other technical guidance procedure (Surface Coal Mining Land Conservation Act, 1981. Illinois Public Act 81‐1015). The objective of this study was to evaluate a wide range of corn (Zea mays L.) genotypes grown on mined land compared to corn grown on an adjacent natural soil. Forty corn hybrids in 1984 and 38 hybrids in 1985, with 29 hybrids being common to both years, were planted on two reclaimed soils and an undisturbed tract. The two mine soils consisted of: (i) 45 cm of topsoil replaced over graded wheel spoil, and (ii) graded wheel spoil only. Both soils are Typic Udorthents. A nearby tract of Sable soil (fine‐silty, mixed, mesic Typic Haplaquoll) was used as the unmined comparison. Results indicate that hybrid yield variation is associated more with weather variation on mine soils than on the undisturbed Sable soil. Pollination dates were delayed, and yield potential varied among hybrids grown on these disturbed soils. Those hybrids with the highest yield potential on the Sable soil did not necessarily produce the highest yields on the disturbed soils. No significant yield response to topsoil replacement was observed for any hybrid in 1984, and only one hybrid had a significant positive response and two hybrids responded negatively to topsoil replacement in 1985.

Combining Ability of High Lysine Sorghum Lines Derived from P‐721 Opaque

The P‐721 opaque (P‐721Q) endosperm of sorghum [Sorghum bicolor (L.) Moenchl has better protein quality (lysine/protein ratio) than normal sorghum endosperms. However, sorghum with opaque endosperm has not been readily accepted for wide cultivation due to its lower yield potential and some other problems associated with its soft endosperm. The objective of this study was to determine whether hybrids between high yielding opaque lines resulted in heterotic response for grain yield and kernel weight without loss in protein quality. Each of 10 high lysine lines derived from P‐721Q was mated with the same three cytoplasmic male‐sterile lines, also derived from P‐721Q by backcrossing to sterile cytoplasm. The F1 hybrids derived from these matings were field‐evaluated for grain yield, 100‐kernel weight, protein concentration, and lysine concentration in protein on a fine‐silty, mixed, mesic Typic Haplaquoll. Significant differences among general combining ability effects were observed for all characters except grain yield, whereas significant differences among specific combining ability effects were observed for only grain yield. Correlation between grain yield and protein in the 30 hybrids was negative and significant (r = −0.63); correlation between grain yield and lysine concentration in protein was also negative but not significant. The best male parent, R‐3 (P‐850314), also produced hybrids with the highest lysine concentration. Among the female parents, A‐3 (P‐851063) gave hybrids with the highest protein quality. The best single‐cross hybrid, A‐3 ✕ R‐3, for agronomic and protein quality, had 35% more lysine than the normal cultivar P‐721N and yielded as much as the NK‐180 check. Thus, this hybrid has the potential of substituting for other expensive protein and lyslne sources in the semiarid tropics.

Measuring Seed Yield in Soybean Populations Segregating for Male Sterility1

Using genetic male sterility to facilitate intermating in a recurrent selection scheme requires that either the male‐sterile allele be removed from the population before yield testing or that the effects of male‐sterile plants be known and considered in evaluating seed yield. This study was conducted to determine the effect of male‐sterile plants on seed yield and to test methods of estimating the yield of fully fertile plots from data collected on plots segregating for male sterility in soybean [Glycine max (L.) Merr.] populations. Nine F2 populations were grown in both hill and row plots. Each population was tested with and without segregation for genetic male sterility. Plots were established, in a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudolls) in 1981 and a Drummer silty clay loam (fine‐silty, mixed, mesic Typic Haplaquolls) in 1982. Data were collected on maturity, seed yield, and number of fertile and sterile plants. The yield of plots segregating for male sterility was adjusted by four procedures: (i) mean yield of fertile plants ✕ total number of plants, (ii) plot yield divided by 0.75, (iii) least square means (LSM) calculated using total number of fertile plants as a covariate, and (iv) LSM calculated using total number of fertile plants and total number of plants as covariates. Seed set was very low on male‐sterile plants and the presence of male sterility significantly reduced yield. Methods of adjusting the yield of plots with male‐sterile plants were more successful with hill plots than with row plots. The presence of male sterility is a complicating factor in measuring seed yield and the statistical procedures tested did not successfully remove the detrimental effect of barren or near‐barren plants.

Influence of Prestress Environment on Annual Bluegrass Heat Tolerance1

Annual bluegrass (Poa annua L.) turf quality is reduced during periods of high temperature. To predict heat stress injury and develop improved prestress maintenance practices, an understanding of the seasonal variation in annual bluegrass heat tolerance and the influence of soil moisture on heat tolerance is crucial. Annual bluegrass growing in the field on a Drummer silty clay loam (fine silty, mixed, mesic Typic Haplaquolls) was sampled on 23 dates over two growing seasons and brought to a laboratory for exposure to high temperature. Prestress environmental conditions (air and soil temperature, soil matric potential, plant water potential, daylength, rainfall and irrigation) were monitored. Plants were enclosed in plastic bags, exposed for 30 min to temperatures in the range 40 to 48°C in a water bath and placed in a greenhouse for a 2‐week recovery period. The dry weight of the stressed plants expressed as a percentage of the controls (heat tolerance indices, HTI) was used as a measure of heat tolerance. In a second experiment, field plots of annual bluegrass were maintained for one growing season under either a dry (rainfall plus irrigation to prevent severe wilting) or moist (dry treatment plus 10‐mm irrigation every other day) soil regime. Plants were stress‐tested on five dates when differences in soil matric potentials existed between treatments, and on five dates when matric potentials were identical (saturated soil). Turfgrass color, quality, and rooting depth were monitored. The best equation fitted to HTI using the results of the first experiment was: y = 15.6 ✕ A + 9.85 ✕ B − 0.22 ✕ A2 − 0.31 ✕ B2 − 0.25 ✕ A ✕ B ✕ 194.71 (R2 = 0.78, p = 0.0001), where A = mean maximum daily air temperature (°C) for the 2 days preceding sampling and B = mean total precipitation (mm) of the period 2 through 4 days prior to sampling. The second experiment revealed a nonsignificant trend for annual bluegrass maintained under moist soil conditions to be less heat tolerant than that under dry conditions. No differences were found due to treatment in rooting depth which negatively correlated (r = −0.83) with the soil temperature at 10 cm. Because of reduced turfgrass quality with the dry soil conditions, there appeared to be little potential for increasing heat tolerance through irrigation management.

A Nitrogen‐15 Microplot Design for Measuring Plant and Soil Recovery of Fertilizer Nitrogen Applied to Corn1

AbstractApplication of the stable isotope I5N to a small area, or microplot, within a larger field plot reduces the cost of measuring plant uptake and soil recovery of fertilizer‐derived N (FN). The objective of this study was to evaluate a specific microplot design for corn (Zea mays L.), including determining maximum plant sampling area. Nitrogen as (NH4)2SO4 was applied to 6‐ by 9‐m plots of corn at rates of 200 and 150 kg N ha−1 on a Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll) and a Mt. Carroll silt loam (fine‐silty, mixed, mesic Mollic Hapludalf), respectively, in 1982 and 1983. Enriched 15N was applied to 1.52‐ by 2.29‐m microplots located in opposite halves of the large plot in each year of the study. This allowed separate measurement of plant and soil recovery of FN for the two application years as well as for residual years. Each microplot was centered lengthwise on one row and bordered by the two adjacent rows, so that the center row was 0.76 m from each side of the microplot and the adjacent rows were on the microplot edge. To assure incorporation and uniform distribution, labeled N solution was injected with a syringe to a depth of 0.08 m on a grid pattern with 0.19‐m spacings. Grain and stover samples and soil samples to a 0.4‐m depth were taken at maturity from various positions within and outside the microplots, and percentage of N derived from fertilizer was determined. Results showed that this microplot design provided reliable FN recovery data for corn in 0.76‐m rows when plant samples were taken from the center row at least 0.38 m from the end of the microplot and when soil was sampled from a 0.76‐ by 1.14‐m area in the center of the microplot. Measurement of FN in plants from the two edge rows indicated that use of a microplot 0.76 m in width would not always provide reliable FN data.

Influence of Weather on Year‐to‐Year Yield Response of Corn to Ammonia Fertilization1

AbstractMulti‐year N studies have shown large year‐to‐year variation in the yield response of corn (Zea mays L.) to N fertilization. The objectives of this study were to (i) determine which normally predicted and measured weather variables account for this year‐to‐year variability; and (ii) to suggest a climate forecast design that will provide the most flexibility in planning N fertilization programs. Relative yield responses to N treatments were obtained from 6 yr of field research on a fine, silty, mixed mesic Typic Haplaquolls. Relative yields and spring N treatments were transformed using natural logarithms (In). The transformed N treatments accounted for more than 95% of the transformed yield responses in 5 of the 6 yr. The only year the regression failed to fit accurately was a very hot, dry year when there was a negative response to N. The analog of the equation was used to obtain α and β coefficients, where α is the fraction of maximum yield expected if no N is applied, and β is the rate of yield increase with each additional unit of applied fertilizer. The α and β values were then related to the ratio of precipitation/evaporation (P/E) from the 11 June to 15 July period in each of the 6 yr. The quadratic relationship explained 99% of the variation in α and 95% of the variation in β. When P/E is less than optimum, water is limiting and the plant is unable to use the applied nitrogen efficiently. When P/E is greater than optimum, N may be lost through denitrification and/or leaching and is thus, unavailable to the plant.

Dry Matter Partitioning as Influenced by Competition Between Soybean Isolines1

AbstractIntergenotypic competition has been shown to bias estimates of seed yield among soybean [Glycine max(L.) Merr.] genotypes. It is unknown how early in plant development intergenotypic competitive effects occur and what plant parts are affected. The objectives of this research were to determine what plant characteristics were affected by intergenotypic competition and how early in plant development these effects could be detected. Two soybean isolines ‘Clark’ and ‘Clark‐e2’, which matures 14 days earlier than Clark, were grown in hill plots at two spacings, 0.38 and 0.76 m between hills in 1981 and 1982. Plots were grown at Lafayette, IN on a Chalmers soil (finesilty, mixed, mesic Typic Haplaquoll). Three areas of hills were planted, (i) all hills of Clark, (ii) all hills of Clark‐e2, and (iii) alternate hills of Clark and Clark‐e2. At the fourth trifoliolate stage and at 2‐week intervals thereafter, three adjacent hills of Clark, of Clark‐e2, and three hills of each isoline in the area planted to alternate hills were harvested. Dry weight of stems, leaves, and pods plus seeds were recorded. Results were similar for the two spacings. Stem weight of Clark was significantly greater when bordered by Clark‐e2than when self‐bordered from the time of initial seed development through maturity. Stem weight of Clark‐e2was unaffected by the phenotype of surrounding plants. Leaf weight of Clark was significantly greater when bordered by Clark‐e2than when self‐bordered from the time of initial seed development until leaves began to yellow and drop. Like stem weight, leaf weight of Clark‐e2was unaffected by the phenotype of the surrounding hills. Competitive effects for pod weight (including seeds) were apparent throughout pod and seed development to maturity. Pod weight of Clark was enhanced and of Clark‐e2was depressed when the two genotypes were grown in alternate hills.

Poorly Drained Conditions and Root Development of Eight Indeterminate Soybean Cultivars1

AbstractThe productivity of soybeans [Glycine max(L.) Merr.] grown on the poorly drained, finely textured soils of southwestern Ontario is often limited by excess spring rainfall. Identifying cultivars able to withstand these conditions may improve productivity. The objective of this experiment was to determine if the effect of poorly drained, non‐flooded conditions on the early root growth of soybeans varies between cultivars. ‘Amcor’, ‘Beeson 80’, ‘Corsoy’, ‘Hawkeye 63’, ‘Harosoy 63’, ‘Kentland’, ‘Premier’, and ‘Wayne’ soybean cultivars were evaluated. Drainage treatments were imposed by maintaining 0.0 to 0.002 m or 0.002 m to 0.0028 m aggregate fractions of Brookston clay loam (clayey, mixed, mesic Typic Haplaquolls) at < 0.02 MPa suction. Plants were grown until 21 days after emergence in 0.0762 m i.d. by 0.92 m long acrylic tubes immersed in 23 °C constant temperature baths located in a controlled environment room. Daytime (16 h) ambient temperatures were maintained at 27 °C and night temperatures at 20.0 °C. Response variables analyzed were the rate of taproot and lateral root extension with time, the number of upper lateral roots with depth, and top and root dry weight. The poorly drained treatment significantly reduced the rate of taproot and lateral root extension; however, the magnitude of the response varied between cultivars. Premier and Harosoy 63 exhibited the largest and Corsoy the smallest reduction in root extension. The number of upper lateral roots was not significantly affected by the drainage treatments. The top/root ratio was significantly higher for the poorly drained treatment due to a greater reduction in root than in shoot dry weight. The results indicate that soybean cultivars differ in their ability to withstand poorly drained conditions during vegetative growth.

Soil Moisture Effects on Root Growth and Phosphorus Uptake by Corn1

AbstractWhile the effects of soil moisture and P level on corn (Zea maysL.) root growth and P uptake have been measured, the extent each of the mechanisms involved in P uptake is affected by soil moisture has not been determined. The objective of this study was to investigate the effect of soil moisture on each of the parameters used in a mechanistic mathematical model to predict P uptake by corn. The effect of volumetric soil moisture, 0.22 (M0), 0.27 (M1), and 0.32(M2), the water held at potentials of −7.5, −33, and −170 kPa, respectively, and three soils (S0and S1, Raub, fine‐silty, mixed, mesic Aquic Argiudolls and S2, Chalmers, fine‐silty, mixed, mesic Typic Haplaquolls, silt loams) obtained from plots having different longtime P histories, on root growth and P uptake by corn was investigated in a series of pot experiments in a controlled climate chamber. As soil moisture was raised from M0to M1, total plant weight increased by 13 to 43%, total P uptake by corn increased by 55 to 70%, and corn root length increased 41 to 52% with the three soils for measurements made at 28 days. Raising soil moisture content further from M1to M2, in contrast, decreased total plant weight by an average of 13%, total P uptake by an average of 15%, and root length by an average of 16% at 21 days. Root surface area and mean P influx, which both increased as soil P increased, were correlated with P uptake. These correlations suggest that increasing soil P increases P uptake, both by increasing P influx and root growth. Raising soil moisture from M0to M1increased P uptake by increasing root growth. Soil moisture did not significantly (P<0.05) affect P influx. Using data for three moisture levels on three soils, predicted P uptake (y) in µmol pot−1calculated with the simulation model for corn grown for 7, 14, and 21 days agreed with observed P uptake (x) (y= 0.78x+ 10.93; r= 0.975**, significant at the 0.01 level).

Soil Moisture Effect on Potassium Uptake by Corn1

AbstractSoil moisture influences K uptake by corn (Zea maysL.) by affecting root growth rate and the rate of K diffusion in soil. The extent each affects K uptake has not been resolved. The objective of this study was to determine the effect of soil moisture on each of the parameters of a mechanistic‐mathematical model that simulates K uptake by corn. Corn was grown for 7, 14, and 21 days at three volumetric soil moisture levels, 0.22 (M0), 0.27 (M1), and 0.32 (M2), the water held at potentials of −7.5, −33, and −170 kPa, respectively, with three soils (S0and S1, Raub, fine‐silty, mixed, mesic Aquic Argiudolls, and S2, Chalmers, fine‐silty, mixed, mesic Typic Haplaquolls, silt loams; S0was low in K, S1and S2were medium in K), in 3‐L pots in a controlled‐climate chamber. Root growth and K uptake by corn were measured. Raising soil moisture from M0to M1increased shoot K uptake by 81, 70, and 68%, with the S0,, S1, and S2soils, respectively. Raising soil moisture further, from M1to M2resulted in a further increase of 13% in K uptake by corn with the S0soil but small decreases of 13 and 8%, with the S1and S2soils, respectively. Raising moisture from M0to M1also increased root growth, however a further increase to M2decreased root growth. There was a relation between root surface area and K uptake, but this varied with soil. The relation between mean K influx and K uptake (r= 0.85**, significant at the 0.01 level), however, was independent of soil. Soil moisture did not significantly (P<0.05) affect K influx. Raising soil moisture from M0to M2, increased the effective diffusion coefficient, De, for K an average of 2.1 times across the three soils. When all the data were used in the simulation model, calculated K uptake (y) in mmol pot−1agreed with observed K uptake (x) by corn (y= 0.9x‐ 0.08; r= 0.95**), indicating that the model is a useful method for studying the effect of soil moisture on each of the mechanisms involved in K uptake by corn.

Seed Yield Response of Three Switchgrass Cultivars for Different Management Practices1

AbstractSwitchgrass (Panicum virgatum L.) is a valuable warm‐season native forage grass in Midwest grazing systems prompting interest in seed production to obtain adequate amounts of seed for planting purposes. Switchgrass seed production studies, however, have been primarily conducted in the Great Plains states. This study was conducted to evaluate cultivar response to row spacing and N fertilization for increasing seed yields in a more humid area of the species' natural adaptation. ‘Cave‐in‐Rock’ (C), ‘Blackwell’ (B), and ‘Pathfinder’ (P) switchgrass were established on a Webster loam (fine‐loamy, mixed, mesic Typic Haplaquoll) soil near Ames, IA, in 1978 in 20‐, 60‐, and 100‐cm rows and fertilized with N at 0, 90, and 180 kg ha−1 in 1979 and 1980. Seed yield and selected seed yield components were measured in 1979 and 1980. Seed yields averaged over 2 years, three N levels and three row spacings were 908, 319, and 388 kg ha−1 for C, B, and P, respectively. Greater lodging resistance, and greater seed yields in response to increased N level and decreased row spacing, contributed to the significantly greater seed yields of C. Seed yields of B and P were similar for all N and row‐spacing treatments. Cultivar rankings in percent fertile tillers varied between years. Inflorescences per unit area did not differ among cultivars, but total seed weight infloresence−1 averaged over years was 268 g for C, which was 54 and 40% greater than for B and P, respectively. Total seed weight inflorescence−1 seemed to be the most important seed yield component, followed by 100 seed weight for explaining seed yield differences among cultivars. Cave‐in‐Rock showed superior lodging resistance and a greater potential for increased seed production in narrow rows and at higher N levels in 2‐ and 3‐year‐old stands. Results showed that N management and row spacing of young stands of switchgrass grown for seed production in the humid Midwest varied according to the cultivar used. Cultivar susceptibility to lodging may be the most limiting factor to obtain high seed yields of some cultivars in the more humid areas of natural adaptation of switchgrass.

Foliar Applications of Nutrients on Maize. II. Physiological Responses1

AbstractDetailed analyses of plant and plant parts during the grain development period could establish mechanisms by which foliar fertilization, especially N, affects productivity of maize (Zea maysL.) hybrids. Field‐grown maize hybrids were sprayed at various stages of development with a mixture of nutrients (N‐P‐K‐S) in 1981 or urea in 1982 to determine whether foliar application of N would delay the remobilization of leaf N and leaf senescence thereby increasing productivity. In 1981, N‐P‐K‐S (12 kg N ha−1per treatment) was applied to plants of five hybrids at 7 days before and 12 days after anthesis. In 1982 urea (two equal applications for a total of 67 kg N ha−1) was applied to three hybrids B73 × Me17, Pioneer brand 3382, and Farm Services brand 854, at 12 and 6 days before anthesis and 9 and 15 and 25 and 32 days after anthesis to give treatments 1, 2, and 3, respectively. Soil type was Drummer silt loam (fine‐silty, mixed, mesic Typic Haplaquoll) in 1981 and a Flanigan silt loam (fine, montmorillonitic, mesic Aquic Arqiudoll) in 1982. The overall lack of effect of the fertilizer spray treatments on plant metabolism in 1981 was attributed to the small amount of supplemental nutrients applied. In 1982, changes in reduced N and nitrate of leaves, stalks, and whole plants were measured between anthesis and physiological maturity. These changes showed that the first urea treatment interfered with both nitrate uptake and assimilation for P3382 and assimilation for B73 × Mo17 and FS854. The second and third treatments had less effect on nitrate uptake and assimilation for all hybrids. The larger increases in stalk reduced N for all hybrids in response to the first urea treatment, compared to the second and third treatments, indicated that in the absence of a rapidly developing ear the stalk served as a storage reservoir for additional N. Urea applications caused no consistent increase, or alteration of the normal postanthesis decline, in the reduced‐N content of the leaves. The immediate decreases and trends in stalk carbohydrate contents show that the first two urea treatments interfered with the accumulation of carbohydrates, especially for P3382 and B73 × Mo l7. The observations that urea sprays did not increase N content of the leaves, decreased the accumulation of carbohydrates by the stalks, and appeared to interfere with indigenous N metabolism help explain the general ineffectiveness of foliar‐N treatments of maize.

Yield and Yield Components of Sorghum and Soybeans of Varying Plant Heights when Intercropped1

AbstractA 2‐year field study was conducted to examine the effects of different sorghum (Sorghum bicolor L. Moench) plant heights on yield and yield components of both sorghum and soybeans (Glycine max L. Merr.) and to compare production of intercrop and monoculture cropping systems. In 1977, ‘Amsoy 71’ soybeans were planted with a short (1.2 m) and a tall (1.6 m) sorghum cultivar in alternate 0.38 m rows on a Drummer silty clay loam (Mollisol, fine‐silty, mixed, mesic Typic Haplaquoll). In 1978, two short (1.3 m) and two tall (1.6 m) sorghum cultivars were intercropped with four soybean cultivars in 0.4 and 0.8 m rows on a Coto clay (Oxisol, clayey, kaolinitic, isohyperthermic Tropeptic Haplorthox). Soybean yields with tall sorghum were 71 and 18% less than those with short sorghum for 1977 and 1978, respectively. These reductions were due to fewer pods/plant in both years, fewer seeds/pod in 1978, and decreased seed weight in 1977. Narrow rows increased soybean yields 50% with short sorghum and by 35% with tall sorghum in 1978. Intercrop tall sorghum yields were greater than short sorghum yields by 86% in 1977 and 74% in 1978. All yield components except plants/ha contributed to the increase in 1978. Intercrop soybean yields were 37 and 69% of monoculture yields in 1977 and 1978, respectively. Intercrop sorghum yields were 40 and 45% of monoculture yields in 1977 and 1978, respectively. Land equivalent ratios were not different in 1977, but in 1978 they were greater with tall sorghum than with short sorghum, 1.17 vs 1.10, and were greater in intercrop than in monoculture, 1.14 vs 1.00.

Phosphorus and Potassium Uptake of Field‐Grown Soybean Cultivars Predicted by a Simulation Model

AbstractMathematical models for calculating nutrient uptake by plants grown in soil have been successfully verified in pot experiments. However, few attempts have been made to verify the models for predicting nutrient uptake under field conditions. The Cushman mathematical model was tested for prediction of P and K uptake by soybeans (Glycine max L. Merr.) grown in the field; five cultivars were grown each year for 3 years. Experimental site varied with year. The soils used were Raub silt loam (fine silty, mixed, mesic Aquic Argiudolls) and Chalmers silt loam (fine silty, mixed, mesic Typic Haplaquolls). Observed P and K uptake was obtained from plant analysis. Root system size was obtained by taking soil core samples, washing the soil from the roots, and measuring root length and mean root radius. Root kinetic parameters for P and K influx were measured in solution culture experiments conducted in a controlled climate chamber. Soil nutrient supply parameters were measured in the laboratory on surface and subsoil samples. The model accurately predicted K uptake by the different cultivars grown in both soils and P uptake from the high‐P (52 µM in the soil solution) Chalmers soil. Prediction of P uptake from the low‐P (7.8 µM in the soil solution) Raub soil was 30 to 35% of the observed P uptake, even though predicted uptake by root hairs was included in the calculation. The difference may have been partly due to acidification of the rhizosphere soil by root exudate, which increased P concentration in soil solution and consequently increased P uptake.

Nitrification of Anhydrous Ammonia Related to Nitrapyrin and Time‐Temperature Interactions1

AbstractThe effects of time and temperature, with and without nitrification inhibitor, were evaluated on the rate of nitrification for field‐applied anhydrous ammonia on a Webster clay loam soil (fine loamy, mixed, mesic Typic Haplaquoll) in central Iowa. The purpose of the study was to document factors influencing the production of oxidized N, forms of N more easily lost from the soil by leaching or denitrification. Anhydrous ammonia at 180 kg N/ha was applied at three application dates in the fall of 1979 (9 October, 27 October, and 14 November) and three application dates in the spring of 1980 (15 April, 2 May, and 25 June). Plots with and without 0.56 kg/ha nitrapyrin were established on each date. Ammonium was found to be concentrated within a 5‐cm radius of the injection zone. The accumulation of heat units (HU), calculated by the summation of temperature (°C) multiplied by time (days), was shown to have a negative correlation with recoverable NH4‐N and followed the equation: %NH4‐N = −0.07 HU + 76.4, R2= 0.84*, significant at the 0.05 level. Thus, much of the variability of recovered NH4‐N could be explained by a time by temperature interaction. This suggests that a grower's decision to apply anhydrous ammonia in the fall when soil temperatures reach a given level, commonly 10˚C, should be tempered by the date. In early fall, more time is available for nitrification to occur before freezing of the soil, and a greater conversion of NH4‐N to N03‐N would be expected. In the presence of a nitrification inhibitor, higher percentages of NH4‐N were recovered for a similar heat‐unit accumulation. Regression equations predicted an 84% recovery with 233 accumulated heat units in the presence of nitrapyrin, compared with a 60% recovery without nitrapyrin. For an equal percentage of NH4‐N recovery the following spring, a grower could apply anhydrous ammonia earlier in the fall if nitrapyrin was used. According to the equations developed in this study for the 1979‐1980 season, a 9 October application of anhydrous ammonia with nitrapyrin would have resulted in approximately a 70% NH4‐N recovery in the spring of 1980, compared with the same recovery for a 23 November application without nitrapyrin.

Effect of Nitrapyrin on Nitrogen Transformations in Soil Treated with Liquid Swine Manure1

AbstractApplications of animal manure to soil result in nitrification of applied NH+4 — N and eventual loss of applied N through leaching and/or denitrification processes. In theory, one way to reduce the leaching and/or denitrification losses is through the use of a nitrification inhibitor. Therefore, a field experiment was conducted during the summer of 1979 to determine the effects of nitrapyrin [2‐chloro‐6(trichloromethyl)pyridine] on N transformations occurring within a band of soil‐applied liquid swine manure (LSM). Liquid swine manure (60 t ha −1) containing 0 or 50 mg nitrapyrin active ingredient/liter was injected into Chalmers silty clay loam (fine‐silty, mixed, mesic Typic Haplaquoll). The LSM application provided about 156 kg ha −1 of plant‐available N and nitrapyrin addition rates were 0 and 3 kg ha.−1 Periodically during the 24‐week experiment soil samples were obtained from the LSM application band and analyzed for NH+4 — and NO−3 — N. From 40 to 50% of added organic N was mineralized in the LSM application bands. Ammonium present in bands of LSM not treated with nitrapyrin was oxidized to nitrate within 7 weeks after application. Addition of nitrapyrin to the LSM delayed nitrification for up to 15 weeks after application. Essentially all of the inorganic N had been lost from the LSM that did not receive nitrapyrin by the 11th week after application, probably as a result of sequential nitrification and denitrification. However, in the nitrapyrin‐treated LSM high amounts of inorganic N remained during the entire experiment and greater than 50% of the inorganic N initially present was recovered after 24 weeks. These findings suggest that nitrapyrin was effective in inhibiting nitrification in manure‐treated soil and addition of the inhibitor reduced N losses following manure application.

Tillage Effects on Soybean Nodulation, N2(C2H4) Fixation, and Seed Yield1

AbstractPreviously, tillage has been shown to affect the yield of soybeans in southern Minnesota. The objective of this study was to determine if different tillage treatments also affected soybean nodulation and N2(C2H4) fixation. Six tillage treatments were sampled in 1975, 1976, and 1977 for nodulation and acetylene reduction activity. The six tillage treatments were part of a 12 tillage treatment experiment established in 1973 under a corn‐soybean rotation system on a Webster clay loam soil (fine‐loamy, mixed, mesic Typic Haplaquoll). Yield was significantly affected by tillage treatment with the yield of the no‐till treatment averaging 22% less than the other five tillage treatments. Few differences were noted in nodule number, nodule weight, or total acetylene reduction activity with respect to tillage treatment. Fall tillage tended to increase nodulation and acetylene reduction over spring tillage, but differences were small. Yield differences due to tillage practice were not attributed to changes in the N2‐fixation system of soybeans.

Potassium Fertilization Effects on Phomopsis Seed Infection, Seed Quality, and Yield of Soybeans1

AbstractSoybeans [Glycine max (L.) Merr.] are often damaged by the seedborne fungi Phomopsis sp. and Diaporthe phaseolorum (Cke. and Ell.) Sacc. in regions where the climate is warm and humid during and after maturation. Incidence of these fungi is sometimes decreased by soil application of K fertilizer to improve crop growth. This study was designed to determine if high levels of soil available K, or K fertilizer applications beyond that necessary to maximize yield, would have a significant effect on seed‐borne fungi and seed quality.Soybeans were grown on Granby loamy fine sand (sandy, mixed, mesic Typic Haplaquoll), on Canfield silt loam (fine‐loamy, mixed, mesic Aquic Fragiudalf), and on Crosby silt loam (fine, mixed, mesic Aerie Ochraqualf). Potassium fertilizer was applied at various rates to establish a range of available K in soil. Potassium concentration of leaves closely paralleled K fertilizer treatments and the soil K levels. Seed was harvested from mature plants, and seed‐borne fungi were identified on samples cultured on potato‐dextrose agar. Phomopsis sp. was the most common fungus isolated from soybeans, ranging up to a 63% incidence. Diaporthe phaseolorum occurred with much less frequency, rarely exceeding a 10% incidence.Potassium fertilization nearly always decreased moldy seed, but increased seed germination and yield somewhat less frequently. Where germination was increased by K fertilization, the incidence of Phomopsis sp. and D. phaseolorum nearly always remained unchanged. Thus, K fertilization usually does not influence Phomopsis sp. and D. phaseolorum infection of seed, but possibly limits fungal growth after infection has occurred. Fertilizer rates in excess of that necessary to maximize yield had little influence on germination or moldy seed.Occurrence of Phomopsis sp. was greater in seeds from lower nodes than from upper nodes; whereas, the reverse was true of D. phaseolorum. Even though K deficiency symptoms occurred only on upper fruits and leaves, K fertilization decreased Phomopsis sp. 23 percentage points in lower seeds in contrast to 14 percentage points in upper seeds. Infection of seed by Phomopsis sp. within a plant does not appear to be related to K deficiency symptoms.

Soil Compaction Effects on Soybean Nodulation, N2 (C2H4) Fixation and Seed Yield1

AbstractOften soil compaction is considered undesirable for plant growth and may limit soybean yield. The objective of this study was to determine the effect of soil compaction on soybean plant growth, yield, nodulation, and N2 (C2H4) fixation. Field experiments were conducted for 2 years (1976 and 1977) on a Webster clay loam soil (fine‐loamy, mixed, mesic Typic Haplaquolls). Plots were compacted by 0, 1, 2, or 3 tractor passes over the same area approximately 2 weeks before planting. Soybean biomass and plant height were measured in 1977, but soil bulk density and soybean seed yield were measured in both years. Nodulation and acetylene reduction activity were measured four times during the season for taproots and two times for lateral roots in both years. Bulk density was increased significantly both years by tractor compaction. In 1976, when extremely dry conditions existed throughout the growing season mean seed yield values were greater on the tractor compacted plots (2,161, 2,106, and 2,283 kg/ha for the 1, 2, and 3 tractor pass treatments, respectively) than on the non‐compacted plots (1977 kg/ha), but the yields were not statistically significant. Taproot nodulation and acetylene reduction were also significantly greater on the 2 tractor pass treatment than on the non‐compacted plots, but little difference in lateral root nodulation and acetylene reduction was noted.In 1977, when greater than normal precipitation occurred, compaction decreased significantly plant growth and taproot nodulation and tended to decrease lateral root nodulation. Acetylene reduction was not affected by compaction. The mean seed yield value was greatest in the non‐compacted plot (4,117 kg/ha) and the mean values declined with increasing tractor compaction (4,105, 3,955, and 3,854 kg/ha for the 1, 2, and 3 tractor pass treatments, respectively), although the yields were not statistically different. The effect of soil compaction in the spring prior to planting appeared to be dependent on the amount of precipitation in the growing season.

Foliar Application of P. II. Yield Responses of Corn and Soybeans Sprayed with Various Condensed Phosphates and P‐N Compounds in Greenhouse and Field Experiments1

AbstractGreenhouse and field experiments were conducted with corn (Zea mays L.) and soybeans (Glycine max L. Merr.) to evaluate the growth response of foliar sprays with several condensed phosphates and P‐N compounds. The maximum concentration of P tolerated in solutions of tri‐ and tetrapolyphosphates applied as sprays in the greenhouse was 1.3% with corn and 1.1% with soybeans. The maximum concentration of P tolerated as orthophosphate was 0.5% with corn and 0.4% with soybeans. With soybeans, the yields of plants sprayed with various condensed P compounds significantly exceeded the yields of the unsprayed control, which would not be classed as P‐deficient on the basis of the P content of the leaves. Spraying the plants, however, increased the P concentration in the leaves. Phosphoryl triamide produced the highest yields of above‐ground dry matter of corn plants in an experiment in which several P‐N compounds and condensed phosphates were brushed on the leaves. Several different condensed phosphates were sprayed on corn and soybeans in a field experiment on a fine loamy, mixed, mesic typic haplaquoll (Webster silt loam). An increase in yield of corn that was statistically significant at the 5% level was obtained from spraying. The yields with tri‐ and tetrapolyphosphate were, respectively, 760 and 754 kg/ha above the control yield of 10,234 kg/ha. With soybeans, the increase in yield due to treatment was significant at the 18% level, and the increase was equivalent to 256 kg/ha above the control yield of 3747 kg/ha.