Flanagan Silt Research Articles

No‐Till and Strip‐Till Soybean Production with Surface and Subsurface Phosphorus and Potassium Fertilization

Compared to no‐till, strip‐till can offer improved seedbed conditions and deep banding of fertilizer. The objective of this study was to quantify the effect of rate and placement of P and K in no‐till and strip‐till systems on soybean [Glycine max (L.) Merr.] seed yield. A 3‐yr field experiment was conducted near Urbana, IL, on Flanagan silt loam (fine, smectitic, mesic Aquic Argiudolls) and Drummer silty clay loam (fine‐silty, mixed, superactive, mesic Typic Endoaquolls) soils, with soybean planted following corn (Zea mays L.). Tillage/fertilizer placement was the main plot with no‐till/broadcast (NTBC); no‐till/deep band (NTDB); and strip‐till/deep band (STDB); deep band placement was 15 cm beneath the planted row. Phosphorus–fertilizer rate (0, 12, 24, and 36 kg P ha−1 yr−1) was the subplot, and K‐fertilizer rate (0, 42, 84, and 168 kg K ha−1 yr−1) was the sub‐subplot. Soil water, soil and trifoliate P and K, and seed yield were measured. Overall, STDB produced 3.1 Mg seed ha−1, 10, and 7% more yield than NTBC and NTDB, respectively. Seed yield, number of pods plant−1, and trifoliate P concentration and accumulation increased with P fertilization uniformly across tillage/fertilizer placement indicating that fertilization cannot be reduced with deep band applications relative to broadcast applications without a reduction in seed yield, but deep banding increased subsurface soil test levels. Potassium fertilization decreased seed yield in both no‐till systems but not in the STDB system. While P and K placement produced no differences, improved soybean yield and nutrient accumulation resulted from a tillage effect with STDB relative to the no‐till systems.

Total Nonstructural Carbohydrate Storage in Creeping Bentgrass Treated with Trinexapac-ethyl

Total nonstructural carbohydrates (TNC) are important for summer recuperation from injury for cool-season turfgrass. The objectives of this study were to determine if trinexapac-ethyl (TE) [4-(cyclopropyl-a-hydroxy-methylene)-3,5-dioxo-cyclohexane-carboxylic acid ethyl ester] affects TNC content and turf quality of a creeping bentgrass at various application frequencies and rates and to investigate any interactions between the effects of TE and traffic treatments on TNC content. Field experiments were conducted in 1995 and 1996 on a mature stand of `Pennlinks' creeping bentgrass grown on a Flanagan silt loam soil maintained at a height of 1.9 cm. Treatments included a single application (0.28 kg·ha-1) or repeat applications at 2 (0.06 kg·ha-1) or 4 (one at 0.28 kg·ha-1 and one at 0.09 kg·ha-1) week intervals during the first 8 weeks of each experiment. Treatments were arranged in a strip-plot design with TE applications as whole plots and traffic treatments as strip plots. Traffic treatments began at 2 weeks and 2 days after initial applications in 1995 and 1996, respectively and continued until the last evaluation date. Traffic treatments consisted of 4 passes of a 102.2 kg smooth roller, 2 days·week-1 in 1995 and 8 passes daily in 1996. A single aqueous extraction method was used for quantification of glucose, fructose, sucrose, and fructan. TNC was the total of all analyzed fractions. Single applications of TE at 0.28 kg·ha-1 significantly reduced turf quality for 4 weeks in both experiments. Sequential applications of TE at 0.06 kg·ha-1 exhibited reduced quality compared to the control at 4 and 8 weeks in 1995 and 2 weeks in 1996. When TE was applied once at 0.28 kg·ha-1, there was a significant reduction in TNC from 4 to 8 weeks after treatment. In 1996 when TE applications were repeated at 2 and 4 week intervals at 0.06 and 0.09 kg·ha-1, a reduction of TNC from week 4 to week 14 was observed. After 14 weeks the TNC content showed incremental increases. There was no interaction effect between traffic treatments and TE applications in the verdure TNC in either year. In 1996, verdure TNC content was 6% to 17% lower in plots receiving traffic from weeks 4 to 18. These results suggest that high rates of TE, either sequential or single applications, might reduce turf quality or carbohydrate content. While this study has not examined if this is detrimental, multiple TE applications at low rates may minimize any TNC reduction while providing effective growth suppression for extended periods.

Soil Factor Effects on Tolerance of Two Corn (Zea mays) Hybrids to Isoxaflutole Plus Flufenacet1

Field experiments were conducted at three locations in 2000 and 2001 to evaluate what effect soil characteristics have on sensitivity of two corn hybrids to soil-applied isoxaflutole plus flufenacet. Soil types were a Flanagan silt loam with 3.9% organic matter (OM), a Drummer silty clay loam with 5.0% OM, and a Cisne silt loam with 2.1% OM. Soil pH was adjusted to four target levels, 7.0, at each location. Isoxaflutole plus flufenacet treatments consisted of the recommended rate (1 ×) and two times (2 ×), and four times (4 ×) the recommended rates based on soil type. Additional treatments included 1 × and 2 × isoxaflutole plus flufenacet with 1.1 kg/ha atrazine and S-metolachor plus atrazine as a control treatment. Corn hybrid ‘Garst 8366’ (G8366) was more sensitive to soil-applied isoxaflutole plus flufenacet compared with ‘Garst 8600’ (G8600). Corn injury occurred only at two of three locations. Addition of atrazine to the 1 × and 2 × isoxaflutole plus flufenacet tr...

Early Preplant Application Timing Effects on Acetamide Efficacy in No-Till Corn (Zea mays)1

Metolachlor, dimethenamid, acetochlor, and a commercial premixture of flufenacet plus metribuzin were applied 60, 45, 30, and 15 d before planting (DBP) and at planting (preemergence [PRE]) at Dekalb and Urbana, IL in 1995 and 1996. The soil types were a Drummer silty clay loam (fine-silty, mixed, superactive, mesic Typic Endoaquoll) with 2.8% organic carbon and a pH of 6.5 at Dekalb and a Flanagan silt loam (Fine, smectitic, mesic Aquic Argiudoll) with 2.0% organic carbon and a pH of 6.2 at Urbana. Herbicide and application timing affected giant foxtail control and densities. Neither herbicide nor application timing affected crop injury or grain yield. Test of the main effects showed that metolachlor and flufenacet plus metribuzin were more effective than acetochlor or dimethenamid in controlling giant foxtail at 30 and 60 d after planting (DAP) and in reducing foxtail density at 60 DAP. Giant foxtail control 60 DAP was greater than 80% for both metolachlor and flufenacet plus metribuzin for all applicat...

Direct Measurement of Denitrification Using 15 N‐labeled Fertilizer Applied to Turfgrass

Denitrification losses are a possibility from turfgrass because of frequent irrigation, multiple applications of N fertilizers, and an abundance of readily decomposable organic C in thatch and verdure. Field experiments were conducted to directly measure N 2 and N 2 O evolved from a Flanagan silt loam soil under Kentucky bluegrass (Poa pratensis L.) or creeping bentgrass (Agrostis palustris Huds.). Mass spectrometric procedures were used to analyze atmospheric samples collected from replicated 15 N fertilized turf (49 kg ha -1 ). Data showed that labeled fertilizer N (LFN) losses ranged from 2.1 to 7.3% for N 2 and from 0.4 to 3.9% for N 2 O; that large N 2 and N 2 O fluxes occurred after heavy rainfall events; and that more N 2 was evolved than N 2 O. Emission of gas was detected while standing water was visible within cylinders, suggesting the transfer of gases from the flooded soil to the atmosphere through the turfgrass plants. Evolution of N 2 and N 2 O was greater from creeping bentgrass treated with KNO 3 than urea through the first 3 wk of the experiment, whereas N 2 emission was greater for urea during the last 2 wk of the experiment, presumably because of NO 3 production through nitrification. Nitrous oxide was detected on the day of fertilization with the KNO 3 treatment, and the mole fraction of N 2 O decreased from 0.44 to 0.11 with each weekly application of N.

Effect of Turfgrass on Soil Mobility and Dissipation of Cyproconazole

Previous studies of pesticide fate in turfgrass have found less mobility and more rapid dissipation compared with studies using the same pesticide applied to bare soil. Few direct comparisons of pesticide mobility and dissipation in turfgrass vs. bare soil have been conducted. The mobility and persistence of cyproconazole [α‐(4‐chlorophenyl)‐α‐(1‐cyclopropylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol] on bare soil (Flanagan silt loam; fine, smectitic, mesic Aquertic, Argiudoll) and turf containing varying levels of organic matter was examined under field conditions. Twenty‐centimeter‐diameter polyvinyl chloride (PVC) cylinders were installed in either creeping bentgrass turf (Agrostis palustris Huds.), or in turf in where either 33, 67, or 100% of the thatch and plant material had been removed. Cyproconazole was applied at 403 g a.i. ha−1 on 15 July 1996 and 8 July 1997. Replicate sampling cylinders were removed 2 h after treatment (HAT) and 4, 8, 16, 32, 64, and 128 d after treatment (DAT). Cylinder cores were sectioned into depths and assayed for cyproconazole by gas chromatography. On all sampling days, increasing the amount of surface organic matter decreased the amount of cyproconazole in the 0‐ to 1‐, 1‐ to 3‐, 3‐ to 5‐, and 5‐ to 15‐cm core sections. The amount of cyproconazole detected in the soil under a full stand of turf at 4 and 32 DAT was 1 and 11%, respectively, of that detected in bare soil. Cyproconazole residues never exceeded 20 μg kg−1 in the 15‐ to 30‐cm core section of any treatment. The half‐life of cyproconazole decreased from 129 d in bare soil to 12 d in a full bentgrass turf. Cyproconazole movement below 5 cm in the soil was reduced with increasing amounts of turfgrass thatch, and as little as one‐third of a full stand of turf greatly decreased the half‐life of cyproconazole. Application of cyproconazole to turfgrass results in less mobility and more rapid dissipation than is typically reported in other agronomic crops.

Fate of chlorsulfuron in the environment. 1. Laboratory evaluations

The behaviour and fate of chlorsulfuron in aqueous and soil systems were examined in laboratory studies. Aqueous hydrolysis was pH-dependent and followed pseudo-first-order degradation kinetics at 25°C, with faster hydrolysis occurring at pH 5 (half-life 24 days) than at either pH 7 or 9 (half-lives >365 days). Degradation occurred primarily by cleavage of the sulfonylurea bridge to form the major metabolites chlorobenzenesulfonamide (2-chlorobenzenesulfonamide) and triazine amine (4-methoxy-6-methyl-1,3,5-triazin-2-amine). This route is a major degradation pathway in water and soil systems. Aqueous photolysis (corrected for hydrolysis) proceeded much more slowly (half-life 198 days) than aqueous hydrolysis and is not expected to contribute significantly to overall degradation. Hydrolysis in soil thin-layer plates exposed to light (half-life 80 days), however, progressed at a much faster rate than in dark controls (half life 130 days), which suggests that a mechanism other than direct photolysis may have been operative. An aerobic soil metabolism study (25°C) in a Keyport silt loam soil (pH 6·4, 2·8% OM) showed that degradation was rapid (half-life 20 days). Dissipation in an anaerobic sediment/water system (initial pH of water phase 6·7, final pH 7·4) progressed much more slowly (half-life >365 days) than in aerobic soil systems. Major degradation products in aerobic soil included the chlorobenzenesulfonamide and triazine amine as in the aqueous hydrolysis study. Neither of these degradation products exhibited phytotoxicity to a variety of crop and weed species in a glasshouse experiment, and both exhibited an acute toxicological profile similar to that of chlorsulfuron in a battery of standard tests. Demethylation of the 4-methoxy group on the triazine moiety and subsequent cleavage of the triazine ring is another pathway found in both aqueous solution and soils, though different bonds on the triazine amine appear to be cleaved in the two systems. Hydroxylation of the benzenesulfonamide moiety is a minor degradation pathway found in soils. Two soils amended with 0·1 and 1·0 mg kg-1 chlorsulfuron showed slight stimulation of nitrification. The 1·0 mg kg-1 concentration of chlorsulfuron resulted in minor stimulation and inhibition of 14C-cellulose and 14C-protein degradation, respectively, in the same soils. Batch equilibrium adsorption studies conducted on four soils showed that adsorption was low in this system (Koc 13–54). Soil thin-layer chromatography of chlorsulfuron (Rf=0·55–0·86) and its major degradation products demonstrated that the chlorobenzenesulfonamide (Rf=0·34–0·68) had slightly less mobility and that the triazine amine (Rf=0·035–0·40) was much less mobile than chlorsulfuron. In an aged column leaching study, subsamples of a Fallsington sandy loam (pHwater 5·6, OM 1·4%) or a Flanagan silt loam (pHwater 6·4, OM 4·0%) were treated with chlorsulfuron, aged moist for 30 days in a glasshouse and then placed upon a prewet column of the same soil type prior to initiation of leaching. This treatment resulted in the retention of much more total radioactivity (including degradation products) than by a prewet column, where initiation of leaching began immediately after chlorsulfuron application, without aging (primarily chlorsulfuron parent). © 1998 SCI

Fate of chlorsulfuron in the environment. 1. Laboratory evaluations

The behaviour and fate of chlorsulfuron in aqueous and soil systems were examined in laboratory studies. Aqueous hydrolysis was pH-dependent and followed pseudo-first-order degradation kinetics at 25°C, with faster hydrolysis occurring at pH 5 (half-life 24 days) than at either pH 7 or 9 (half-lives >365 days). Degradation occurred primarily by cleavage of the sulfonylurea bridge to form the major metabolites chlorobenzenesulfonamide (2-chlorobenzenesulfonamide) and triazine amine (4-methoxy-6-methyl-1,3,5-triazin-2-amine). This route is a major degradation pathway in water and soil systems. Aqueous photolysis (corrected for hydrolysis) proceeded much more slowly (half-life 198 days) than aqueous hydrolysis and is not expected to contribute significantly to overall degradation. Hydrolysis in soil thin-layer plates exposed to light (half-life 80 days), however, progressed at a much faster rate than in dark controls (half life 130 days), which suggests that a mechanism other than direct photolysis may have been operative. An aerobic soil metabolism study (25°C) in a Keyport silt loam soil (pH 6·4, 2·8% OM) showed that degradation was rapid (half-life 20 days). Dissipation in an anaerobic sediment/water system (initial pH of water phase 6·7, final pH 7·4) progressed much more slowly (half-life >365 days) than in aerobic soil systems. Major degradation products in aerobic soil included the chlorobenzenesulfonamide and triazine amine as in the aqueous hydrolysis study. Neither of these degradation products exhibited phytotoxicity to a variety of crop and weed species in a glasshouse experiment, and both exhibited an acute toxicological profile similar to that of chlorsulfuron in a battery of standard tests. Demethylation of the 4-methoxy group on the triazine moiety and subsequent cleavage of the triazine ring is another pathway found in both aqueous solution and soils, though different bonds on the triazine amine appear to be cleaved in the two systems. Hydroxylation of the benzenesulfonamide moiety is a minor degradation pathway found in soils. Two soils amended with 0·1 and 1·0 mg kg-1 chlorsulfuron showed slight stimulation of nitrification. The 1·0 mg kg-1 concentration of chlorsulfuron resulted in minor stimulation and inhibition of 14C-cellulose and 14C-protein degradation, respectively, in the same soils. Batch equilibrium adsorption studies conducted on four soils showed that adsorption was low in this system (Koc 13–54). Soil thin-layer chromatography of chlorsulfuron (Rf=0·55–0·86) and its major degradation products demonstrated that the chlorobenzenesulfonamide (Rf=0·34–0·68) had slightly less mobility and that the triazine amine (Rf=0·035–0·40) was much less mobile than chlorsulfuron. In an aged column leaching study, subsamples of a Fallsington sandy loam (pHwater 5·6, OM 1·4%) or a Flanagan silt loam (pHwater 6·4, OM 4·0%) were treated with chlorsulfuron, aged moist for 30 days in a glasshouse and then placed upon a prewet column of the same soil type prior to initiation of leaching. This treatment resulted in the retention of much more total radioactivity (including degradation products) than by a prewet column, where initiation of leaching began immediately after chlorsulfuron application, without aging (primarily chlorsulfuron parent). © 1998 SCI

Nitrogen and Sulfur Fertilization Influences Aromatic Flavor Components in Shrunken2 Sweet Corn Kernels

Dimethyl sulfide (DMS) has been identified as the compound responsible for the characteristic aroma of cooked sweet corn (Zea mays L.) and, along with sugar and water-soluble polysaccharides, is one of the main flavor components in the kernels. Because of the close relationship between DMS and its amino acid precursor S-methylmethionine, the premise was formulated that it might be possible to improve sweet corn aroma and overall eating quality through enhanced production of DMS from increased application of N and S to the crop in the field. Studies were conducted on a Plainfield sand and a Flanagan silt loam to evaluate the effects of N and S fertilization on kernel DMS production in several commercial sh2 hybrids; in the process, the effect of N and S fertilization on various yield and yield component parameters was also determined. Hybrid was the main factor affecting kernel DMS production, although in both soils kernel DMS levels were influenced by significant interactions between hybrid and fertilizer treatments. Kernel DMS content, in response to increasing N fertilization rates, increased by an average of 85% in three of six hybrids in the Plainfield sand and by 60% in two of three hybrids in the Flanagan silt loam. The effect of S fertilization on kernel DMS production was small, with only one hybrid on the sandy soil showing a positive response (38%) to S application, and then in combination with high N rates. Irrespective of N-S fertilization regime, kernel DMS concentrations decreased at both locations by an average of ≈8.5% per day as kernel maturity increased. The results showed that kernel DMS production may be enhanced by N nutrition, independent of N fertilization effects on ear and kernel yields.

N2 fixation and dry matter and N accumulation in soybean lines with different seed-fill periods

A positive relationship generally exists between the duration of seed-fill period (SFP) and seed yield in soybean, but exceptions have been reported. The objective of this research was to determine if differences in N2 fixation or N accumulation could explain inconsistent relationships between duration of SFP and seed yield in soybean. For this study, five experimental soybean (Glycine max L. [Men.]) lines were selected on the bases of differences in SFP and seed yield in previous experiments. The experiment was designed to compare lines differing in both SFP and seed yield, differing in SFP but not seed yield, and differing in seed yield but not SFP. Total N2 fixation, using 15N-dilution techniques; total N accumulation, using a semi-micro-Kjeldahl procedure; and total dry matter accumulation, including all vegetative material abscised before maturity were measured on these lines grown in a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudolls) in 1984 and 1985 at Urbana, IL. Mean dinitrogen fixed ranged from 36 to 76 kg ha−1 in 1984 and from 65 to 113 kg ha−1 in 1985. The percentage of the total plant N derived from fixation ranged from 17 to 35% in 1984 and from 32 to 48% in 1985. Statistically significant differences in seed yield were not detected in this experiment because of the high coefficient of variation associated with the small plot size. High N2 fixation was not related to duration of SFP or previous seed yield classification. Total plant N did not differ among these genotypes. For these soybean lines differences in duration of SFP and previous seed yield classification were not related to total N2 fixation or N accumulation.Key words: Glycine max, harvest index, N partitioning, N2 fixation, seed-fill period

Microbial Populations in an Agronomically Managed Mollisol Treated with Simulated Acid Rain

AbstractA fertile well‐buffered mollisol (Flanagan silt loam, fine montmorillonitic mesic Aquic Argiudoll) under cultivation with corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] was subjected to simulated rain of pH 5.6, 4.2, and 3.0, while moisture‐activated rain exclusion shelters provided protection from ambient rain. Soil was sampled to a depth of 3 cm on four dates throughout the 1985 growing season. The following microorganisms were enumerated by plate counts or most probable number: general heterotrophic bacteria, general soil fungi, free‐living N‐fixing bacteria, fluorescent pseudomonads, autotrophic ammonium‐oxidizing, nitrite‐oxidizing, and thiosulfate‐oxidizing bacteria. The ANOVA was used to determine the combined and individual effects of rain treatments, crop field, and sampling date. Crop field and sampling date affected microbial numbers more than rain treatments. Overall, rain treatment effects were limited to nitrite‐oxidizing bacteria; lower numbers occurred in the corn field in subplots treated with rain of pH 4.2 and 3.0, and in the soybean field treated with rain of pH 3.0. The trend was strongest in June and July. In the corn field in subplots treated with rain of pH 3.0, numbers of thiosulfate‐oxidizing bacteria were higher and numbers of general heterotrophic bacteria were lower; however, these trends were comparatively weak. Rain treatments caused essentially no decrease in soil pH, suggesting that acid rain constituents affect certain microbial populations without causing overt changes in pH. Because they appear to be unusually sensitive, nitrite‐oxidizing bacteria could be used as experimental indicators of changes in soil microbial communities subjected to acid rain.

Nitrogen, Potassium, Sulfur, and Boron Fertilization of Canola

Increased demand and developing infrastructure may result in canola (Brassica napus and campestris) acreage expanding in the midwestern USA. Fertility requirements and critical tissue levels of canola grown in the Midwest have not been reported. The objective of the experiment was to examine current N, K, S, and B fertilizer requirements for canola production in Illinois. These field experiments were conducted at Browns-town, IL (1989 and 1990), on a Cisne silt loam soil (fine, mont-morillonitic, mesic Mollic Albaqualf) and at Urbana, IL (1990), on a Flanagan silt loam soil (fine, montmorilloiutic, mesic Aquic Argiudoll). The fertilizer treatments were: N (60,120,180 lb N/acre in 1989 and 0,60,120,180, and 240 lb N/acre in 1990), K (0 and 125 lb K/acre) at Brownstown only, S (0,10, 20 lb S/acre), and B (0 and 1 lb B/acre). Application of all fertilizers increased concentration of each respective nutrient, but only N affected grain yield. Increasing N rate significantly increased vegetative dry weight at the start of flowering, delayed maturity, and increased grain yield. The calculated optimum economic N fertilizer rate was 225 lb N/acre at Urbana and 236 lb N/acre at Brownstown. At the onset of flowering, whole-plant N concentration less than 3.5 to 4.0% was associated with reduced yields. This may indicate the critical N concentration for canola. Because of the indeterminate growth habit, time of sampling will have to be standardized. Sufficiency levels for Illinois conditions are 2.0 to 3.5% K, 0.4 to 0.5% S, and 20 to 30 ppm B, respectively.

Physiological response of two soybean cultivars to simulated acid rain.

Simulated acid rain has been reported to cause physiological changes in various plant species. Studies were conducted in 1983, 1984, and 1985 to determine the effect, of acid rain on physiological parameters in two soybean [Glycine max (L.) Merr.] cultivars. Simulated acid rain of pH 3.0, 4.2 and 5.6 was applied throughout the growing season to plots protected from ambient rain and grown on a Flanagan silt loam (fine, montmorillonitic, mesic Aaquic Argiudoll). Individual plants were evaluated for CO2 fixation, leaf water potentials, and leaf chlorophyll content. Microplots were evaluated for flowering and podding patterns, and dry matter and N partitioning. Rain pH did not affect CO2 fixation, water potentials, chlorophyll content, seed yield, shoot dry weight, or N accumulation. At pH 4.2 Amsoy 71 produced fewer flowers and pods than at pH 3.0 or 5.6. Abscised leaf dry weight of Amsoy 71 was greater at pH 3.0 and 4.2 than at pH 5.6 pH effects were detected for N partitioning, but these responses were dependent on year and cultivar. No physiological basis for reported soybean yield responses to acid rain of pH 3.0 was identified.

Seed yield and agronomic traits of old and modern soybean cultivars under irrigation and soil water-deficit

An understanding of how soybean [ Glycine max (L.) Merr.] cultivars of diverse yield potential respond to soil water-deficit would be valuable to soybean breeders in planning future selections. Our objectives were to evaluate differences in seed yield and agronomic trait performance under irrigation and soil water-deficit of soybean cultivars that vary in seed-yield potential. Two older, lower-yielding (‘Manchu’ and ‘Dunfield’) and two modern, higher-yielding (‘Williams 82’ and ‘Clark 63’) cultivars were drought-stressed between first flowering and harvest maturity in 1984 and 1985 on a Flanagan (Aquic Argiudoll) silt loam soil at Urbana, Illinois. Averaged over years, seed yields of Williams 82 and Clark 63 were 31 and 9% higher than those of Manchu and Dunfield under irrigation and drought stress, respectively. Relative to the irrigated conditions, the smaller seed-yield differences between the old and modern cultivars under drought stress resulted from smaller differences in pod number per branch. The old and modern cultivars did not differ in their apparent harvest index, plant number, branch number per plant, seed number per pod, and seed weight responses to soil water treatment. Leaf-area index of Williams 82 changed the most, and Manchu the least, in relation to soil water. Leaf-area duration in the lower portion of the crop canopy was increased by drought stress to a similar extent for each cultivar, while the period of reproductive development was shortened by severe soil water-deficit more for Manchu and Dunfield than for the modern cultivars. The results of this study show greater seed-yield increases with irrigation for Williams 82 and Clark 63 than for the older cultivars which were a function of a greater number of pods and increased vegetative biomass.

Tillage and Simulated Rainfall Intensity Effect on Bromide Movement in an Argiudoll

AbstractMovement of Br‐ in a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) managed under five different tillage systems and subjected to three simulated rainfall intensities was documented. Under low (10 mm/h) and medium (25 mm/h) simulated rainfall intensities, movement of Br‐ in the soil profile was not significantly different between moldboard plow, chisel plow, disk plow, para‐till, and no‐till systems. When subjected to a high simulated rainfall intensity, significantly greater Br‐ movement occurred in the soil profile managed under continuous, long‐term no‐till. Greater movement of Br‐ in the no‐till soil was attributed to preferential flow.

Response of three corn hybrids to defoliation of neighboring plants

Hail can cut completely through the whorl of young corn (Zea mays) plants causing complete defoliation. If only a portion of the stand is damaged, defoliated plants are subjected to shading by nondefoliated neighboring plants which benefit from reduced competition for light. Field experiments were conducted in 1986 and 1987 at the University of Illinois on a Flanagan silt loam (Aquic Argiudoll) to determine the relative contribution of both defoliated and nondefoliated plants to yield of the stand. Three hybrids were evaluated: Pioneer 3377, FR27 × FRMo17, and FRB73 × FR25. At the four-leaf stage the following treatments were imposed: cutting through the whorl of all plants 50 mm above ground level to effect complete defoliation (100-DEF) or cutting through the whorl of alternate plants (50-DEF). When compared to nondefoliated controls, the 100-DEF and 50-DEF treatments reduced grain yields on the average by 12.3 and 8.3%, respectively. No hybrid × defoliation interaction was detected for grain yield. With the 50-DEF treatment, compensation by nondefoliated plants was evident in the form of increased ears plant−1 and kernels ear−1, and 100-seed weight depending on the hybrid and year. Increased barrenness was a significant factor in decreased yields of defoliated plants only for FR27 × FRMo17 in one year. Key words: Zea mays L., hail damage, yield components, prolificacy, barrenness

Allelopathy and Autotoxicity in Alfalfa: Characterization and Effects of Preceding Crops and Residue Incorporation

Alfalfa (Medicago sativa L.) is known to be both autotoxic and allelopathic. Greenhouse and laboratory experiments were conducted to determine if ‘WL‐316’ alfalfa exhibits short‐term autotoxicity and long‐term autotoxicity and allelopathy. Long‐term autotoxicity and allelopathy of alfalfa were verified at Urbana, IL, by comparing the germination and growth of alfalfa and sorghum [Sorghum bicolor (L.) Moench] on Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) previously cropped to alfalfa (alfalfa‐soil) and sorghum (sorghum‐soil). Short‐term autotoxicity of alfalfa was investigated by studying the effect of incorporating its roots only and both roots and shoots on the germination and growth of alfalfa in alfalfasoil and sorghum‐soil. The data were further supported by a laboratory bioassay of seedling exudate and shoot leachate of alfalfa and sorghum. Plant height and fresh weight per plant of alfalfa and fresh weight per plant of sorghum were lower on alfalfa‐soil than on sorghum‐soil. Germination percentages of both alfalfa and sorghum and plant height of sorghum were unaffected by the preceding crop. The two soils differed in nutrient content, but fertility was high and should not have been limiting to the growth of either crop. As a result, allelopathic/autotoxic compounds in alfalfa‐soil were implicated in the growth inhibition of the two crops. Soil incorporation of fresh alfalfa roots only or both roots and shoots reduced alfalfa emergence, plant height, and dry weight per plant. Primary effects of water‐soluble inhibitory compounds from alfalfa shoot appeared to be on germination and radicle elongation, the latter being apparently more sensitive than the former. Alfalfa allelopathy seems to be more severe than autotoxicity. A flow diagram describes different kinds of allelopathy and autotoxicity and various situations that verify the existence of a particular kind of allelopathy or autotoxicity

Lack of physiological response of two corn hybrids to simulated acid rain

Simulated acid rain has been reported to cause physiological changes in various plant species. Studies were conducted in 1983, 1984 and 1985 to determine the effect of acid rain on some physiological parameters in two corn ( Zea mays L.) hybrids. Simulated rain of pH 3.0, 4.2, and 5.6 was applied throughout the growing season onto plots protected from ambient rain and grown on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll). Individual plants were evaluated for change in leaf CO 2 fixation, water potentials, chlorophyll content, and in vitro pollen germination. Rain pH did not affect any of these parameters. Within the limits of experimental error, it must be concluded that simulated acid rain of pH 3.0 did not affect the physiological parameters measured in this study.

Effect of Method and Plant Sample on Nitrogen Fixation Estimates in Soybean

AbstractThe labor involved in collecting total plant dry matter limits the number of soybean [Glycine max (L.) Merr.] genotypes that can be evaluated for N2 fixation. Therefore, a 2‐yr experiment was conducted on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) to determine if genotypic differences in plant N derived from fixation (N2 fixed) and percentage of plant N derived from fixation (% Ndfa) could be detected by isotope dilution or difference (total N) method analysis of whole plant samples (whole plant sample including abscised material), shoot samples (whole plant samples‐abscised material), or seed samples. Five experimental soybean lines derived from a ‘Williams’ ✕ ‘Kanrich’ cross and ‘Harosoy’ were tested. Estimates of N2 fixed and % Ndfa generated by isotope dilution analysis of whole plant samples ranged from 36 to 113 kg ha−1 and 17 to 48%, respectively. More genotypic separations were possible with isotope dilution than with the difference method. Separation on the basis of % Ndfa by isotope dilution was not affected by plant sample. More genotypic separations on the basis of N2 fixed were possible by isotope dilution analysis of whole plant or shoot samples than by analysis of seed samples.

Melamine/urea and oxamide fertilization of Kentucky bluegrass

Abstract The commercial lawn care industry represents a large market for N sources. A formulated melamine (2,4,6‐triamino‐s‐triazine) plus urea combination (MLU) (45% melamine by weight) and oxamide were evaluated for use by the lawn care industry by comparing turfgrass response from these fertilizers to that from urea, sulfur coated urea (SCU), ureaformaldehyde (Nitroform), and a non‐fertilized check. Fertilizers were applied four times per year to field plots of Kentucky bluegrass (Poa pratensis L.) growing on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) at a rate of 49 kg N ha‐1 per application. Color ratings and clipping weights were determined weekly during the growing season. Trends in color ratings paralleled those in clipping weights. During the first year of the study, MLU treated turf received significantly higher color ratings than nonfertilized turf on only 38% of the rating dates; this increased to 76% in the third year of the study. Color ratings for MLU fertilized tu...