bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining Nitrate in Forage Samples by Xylenol Nitration1
Authors: Sabatka L. D. , Hyder D. N. , Cole C. V. , Houston W. R.
Published: July 2010

The xylenol method of determining nitrates in water samples was reported to provide advantages of rapidity, specificity, sensitivity, and reproducibility. Since most methods of determining nitrates in forage samples are difficult and time consuming, our objective was to adapt the xylenol method for determining nitrates in forage and to compare it to the nitrate‐electrode method.

The first problem originated from an incorrect procedural suggestion concerning the ratio of sulfuric acid to water in the nitration medium. The original recommendation for six parts of sulfuric acid to four parts of water and two parts of acetic acid was satisfactory.

The second problem was one of clarifying plant extracts without adding interfering ions or removing nitrate. A source of bone black adsorbed plant pigments without adsorbing nitrate.

The third problem was that of interference from sugar, which required quantitative evaluation. Although the amount of that interference was small, amounting to 5.4 ppm of nitrate N per 1% sugar extracted from plant dry matter, it was important in the comparison of xylenol and nitrate‐electrode methods. A rapid colorimetric method of determining extracted sugar by darkening with sulfuric acid was developed.

Among triplicate determinations of 12 forage samples ranging from 87 to 1,469 ppm of nitrate N, the xylenol and nitrate‐electrode methods gave equal values and time requirements, but the standard deviation for repeatability was ± 29 ppm by the xylenol method and ± 63 ppm by the nitrate electrode. Consequently, the xylenol method was considered sufficiently accurate, rapid, and precise for routine determinations of nitrate concentrations in forage samples.
Critical Available Soil Phosphorus Level of Indian Soils in Relation to Protein Quality of Wheat
Authors: Khera M. S. , Kapoor H. C. , Gupta Y. P.
Published: July 2010

More information is needed on the relation between the protein quality of wheat and the phosphorus level of the soil on which it is grown. Protein quality of ‘Kalyan Sona’ wheat (Triticum aertivum L.) grown in the greenhouse on 14 alluvial soils was measured by the lysine, methionine, and tryptophan contents of the grain. Quality was inferior when available soil P levels were below 12.5 ppm. Based on this critical level of P, the soils were separated into two groups. The ‘t’ test for protein quality characters of wheat grown on these two groups of soils was highly significant. The importance of soil testing in respect to the need for phosphatic fertilization in maintainng the quality of wheat protein was brought out.
Differential Aluminum Tolerance in Two Snapbean Varieties1
Authors: Foy C. D. , Fleming A. L. , Gerloff G. C.
Published: July 2010

Two snapbean (Phaseolus vulgaris L.) varieties, shown previously to differ in tolerance to acid, Al‐toxic Bladen soil, were tested more specifically for Al tolerance in nutrient cultures. The Bladen soil‐tolerant ‘Bade’ variety was much more tolerant to Al than Bladen‐sensitive ‘Romano.’ For example, with 8 ppm Al added, at initial pH 4.8, top and root yields of Dade were 94 and 107%, respectively, of those with no Al. Corresponding top and root yields of Romano were only 53 and 59%, respectively, of those with no Al.

With 8 ppm Al added, the total Ca uptake values for Dade tops and roots were 98 and 131%, respectively, of those with no Al; corresponding values for Romano tops and roots were only 25 and 22%, respectively. Aluminum added at 6 or 8 ppm also reduced Ca concentrations in tops and roots of Romano by 30 to 50%, but had little effect on those of Dade. Differential Al tolerance was not related to differential pH changes in nutrient solutions or to Al concentrations of plant tops or roots. With 8 ppm Al added the P concentrations in Romano tops and roots were 60 and 14% higher, respectively, than those of Dade.

Aluminum added at 4 ppm decreased stem exudate production of Romano by 66% but did not affect that of Dade. The same Al treatment reduced concentrations of Ca, Mg, K, and P in Romano exudates by 66, 42, 80, and 76%, respectively, but either decreased or failed to affect those of Dade. Lower concentrations of these elements in stem exudates of Al‐injured Romano plants were not associated with immobilization hi roots. The 4‐ppm Al treatment decreased Ca concentrations in Romano root cell walls, mitochondria, supernatant, and total roots by 55, 68, 51, and 43%, respectively. The same treatment decreased the Ca concentration hi Dade root cell walls by only 27% and that in total roots by 8%, and actually increased the Ca concentration in mitochondria and supernatant fractions by 21 and 63%, respectively.

Reduced Ca uptake appears to be a good indicator of Al sensitivity in the two snapbean varieties studied.
Influence of Cool and Warm Temperatures and Temperature Reversal at Inflorescence Emergence on Growth of Timothy, Orchardgrass, and Tall Fescue1
Authors: Knievel D. P. , Smith Dale
Published: July 2010

Timothy (Phleum pratense L.), orchardgrass (Dactylis glomerata L.), and tall fescue (Festuca arundinacea Schreb.) were grown from small propogules in pots of soil in growth chambers to evaluate the effect of temperature and temperature change on flowering, tillering, dry matter accumulation and distribution, and leaf‐blade area accumulation within and among species.

Temperature greatly influenced maturation rate, growth rate, yield, tillering, leaf‐blade area, specific leaf‐blade weight (SLW), and dry matter (DM) distribution within each species. Except for maturation rate and DM distribution, each parameter was highest for all three species in cool (C, 18 C day/10 C night) or warm‐cool (WC, 32 day/24 C night with a change to 18 C day/10 C night at early inflorescence emergence) temperature regimes. Flowering in timothy was not affected by temperature. Significantly fewer flowering culms were obtained in orchardgrass at warm (W, 32 C day/24 C night) compared with C temperatures, while the opposite was true in tall fescue. Late anthesis in each of the grasses occurred first in the W regime and last in the C regime. Maturation rate, after switching from cool to warm (CW, 18 C day/ 10 C night with a change to 32 C day/24 C night at early inflorescence emergence) or warm to cool temperatures (WC) at early inflorescence emergence, varied among the three species. Timothy had the largest increase in maturation rate following the change from C to W temperatures, while that of tall fescue was least affected by the temperature change. Influence of temperature regimes on DM distribution among plant parts varied among species. Timothy was most sensitive to changes from C to W temperatures, while tall fescue was least sensitive. Warm temperatures slowed leaf‐blade area accumulation in orchardgrass and tall fescue in the CW regime and completely stopped it in timothy. Cool temperatures in the WC regimes stimulated leaf‐blade area accumulation in all three grasses. SLW of all three grasses increased with growth stage. Tall fescue had the highest SLW averaged over temperatures and growth stages, followed by orchardgrass and timothy. Change in temperature in the CW regime was followed by a decrease in SLW in each species compared with the C regime, while the opposite was true in the WC compared with the W regime. Timothy, followed in order by tall fescue and orchardgrass, produced the most DM in the C, CW, and WC regimes. Orchardgrass and tall fescue had similar DM yields which were higher than timothy in the W regime. Dry matter accumulation (DMA) rates in corresponding temperatures regimes were similar among species.

It was concluded that the grasses differed in growth and development response to temperature and in sensitivity to temperature change. Differences in total plant yield among the three grasses in comparative temperature regimes were due to differences in DMA rates and in length of growth period.
Effect of Pretransplant Lighting on Post‐transplant Growth and Development of Tobacco1
Authors: Kasperbauer M. J.
Published: July 2010

Uniformity in time of flowering is desirable in tobacco (Nicotiana tabacum L.) production, especially when mechanization is involved. This study was initiated to determine methods of controlling premature floral induction without causing undesirable side‐effects to the plants. Burley tobacco seedlings were treated with various combinations of illumination during the pretransplant period in controlled‐environment chambers and outdoors in modified starting beds. Effectiveness of control was assayed under field conditions.

Early floral induction occurred in seedlings that received high intensity short days and cool temperatures, or low intensity natural daylengths coupled with cool temperatures. When 12‐minute middle‐of‐night interruptions were used, white fluorescent light was more effective than white incandescent light in counteracting a florally inductive environment, while incandescent was slightly more effective than fluorescent when 240‐minute interruptions were used. Twelve minutes of white incandescent light applied in 30‐second increments repeated each 10 minutes during a 240‐minute period were almost as effective as 240 minutes of continuous illumination from the same type of lamps. Night interruptions with white and yellow incandescent light were equally effective. Phytochrome involvement in counteraction of floral induction in tobacco was discussed.

Pretransplant treatments that showed most promise in the controlled‐environments were tested over outdoor starting beds in 1970 and 1971. The first year had a period of cool overcast weather during the treatment period, and the middle‐of‐night supplemental lighting was effective in delaying floral induction. Bright, warm days predominated during the 1971 treatment period, and no premature flowering occurred among either the controls or the treated plants. There were no undesirable sideeffects of the supplemental lighting during either year.

In general, plants that flowered prematurely developed fewer leaves prior to flowering, produced several suckers per plant, were difficult to harvest, and yield of cured leaf was significantly reduced.
Influence of Inoculum Size on Rhizobium japonicum Serogroup Distribution Frequency in Soybean Nodules1
Authors: Kapusta George , Rouwenhorst D. L.
Published: July 2010

Investigations were conducted in 1969 and 1970 to determine the influence of ultra‐high inoculation rates of a single Rhizobium japonicum strain on recovery from soybean (Glycine max (L.) Merr.) nodules. Biological seed yield, nodule mass, seed oil, and protein also were studied. Bacterial suspensions containing up to 1.2 × 1012 rhizobia per cm of row were banded in contact with the seed during planting. A rapid agglutination test was used to distinguish R. japonicum serogroups in homogenized nodule suspensions. Strains 138 and 126 were used as the inoculum in 1969 and 1970, respectively.

Control plot rhizosphere R. japonicum population was between 30,000 and 300,000 per g of oven‐dried soil. The predominant naturalized serogroups in these plots were 123 and c‐1(138) in 1969 and 1970, respectively, despite a distance of only 300 m between test areas. Strain 138 recovery percentage in 1969 increased from 18% in the uninoculated plots to 60% in plots receiving 15 billion rhizobia per cm of row. Similar significant shifts occurred in 1970. The data indicate that it is possible to evoke shifts with at least two serogroups. If superior strains are developed in the future, this technique would be one way to establish them rapidly.

Nodulation, plant growth characteristics, seed yield, and oil and protein content were not influenced by the inoculum rates with one exception. Biological yield was significantly increased in 1970 at the highest inoculum rate. The reason for this observation is not readily apparent.
Double Cropping Systems Involving No‐Tillage and Conventional Tillage1
Authors: Sanford J. O. , Myhre D. L. , Merwine Norman C.
Published: July 2010

This study was prompted by the huge feed grain deficits which increase annually in the Southeast. The need exists to find ways of increasing grain production efficiently. Cropping‐tillage systems designed to accomplish this were studied. Soybeans [Glycine max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench.] were double cropped following wheat (Triticum aestivum L.) on a Blackbelt soil. No‐tillage and conventional tillage methods were compared for soybeans and grain sorghum; Conventional tillage was used for wheat.

The 2‐year average yield of soybeans was 1,708 kg/ha (25.4 bu/acre) for no‐tillage and 2,250 kg/ha (33.4 acre) for conventional tillage. This difference was significant (P = .05) and was due mainly to lack of nutsedge (Cyperus sp.) control by herbicide alone in no‐tillage plots. In the third year when the crop was hand‐hoed, no yield differences occurred due to tillage methods. The 2‐year average yield of grain sorghum was 3,249 kg/ha (48.3 bu/acre) for no‐tillage and 3,868 kg/ha (57.5 bu/acre) for conventional tillage. When the crop was handhoed yield of grain sorghum was significantly higher for no‐tillage (5,072 vs 4.335 kg/ha). Wheat grown after soybeans yielded significantly (P = .05) more than wheat grown after grain sorghum. This difference was attributed primarily to the bneficial effect of residual N from the previous crop of soybeans.

Based on current costs and prices, the soybean‐wheat double cropping system produced significantly higher net returns over specified production costs than the wheat. grain sorghum system.
Establishment Methods for Alfalfa in Irrigated Corn1
Authors: Nordquist P. T. , Wicks G. A.
Published: July 2010

Establishing alfalfa (Medicago sativa L.) under irrigation is expensive and production is low during the establishment year. Our objective was to determine, in the absence of moisture stress and weed competition, which combinations of corn (Zea mays L.) types and alfalfa planting dates would be most productive during the year of planting and the year following establishment. Alfalfa was planted at corn planting time, at last corn cultivation, or after the harvesting of corn for silage. Weed control was obtained by cultivation or using 4‐(2,4‐dichlorophenoxy)butyric acid (2,4‐DB), 2,2‐dichloropropionic acid (dalapon) or S‐ethyl dipropylthiocarbamate (EPTC) without cultivation. Alfalfa stand and yield were increased 27 and 9%, respectively, when alfalfa was planted simultaneously with the corn and the corn harvested as silage; however, this planting method reduced corn silage production from 20 to nearly 50% and grain yields from 1,000 to 3,000 kg/ha compared to alfalfa planted at last cultivation or following silage harvest. Generally ‘Brachytic dwarf’ corn was a poor competitor to alfalfa. Full‐season and midseason hybrids had about the same silage yields, but the full‐season hybrid produced more corn. Under the conditions of our experiment, a midseason corn hybrid planted at 59,000 seeds/ ha, with corn and alfalfa planted at the same time and corn harvested as silage, proved to be an excellent establishment method. This combination gave high silage yields, and removing the corn crop permitted good fall growth of the alfalfa.
Flue‐cured Tobaccos With Varied Ripening Pattern for Modified Harvest Systems1
Authors: Chaplin James F.
Published: July 2010

Mechanically harvesting flue‐cured tobacco (Nicotiana tabacum L.) requires uniform ripening of leaves. Tobaccos are available with varied ripening patterns and a test was conducted to determine which may be more adaptive to varied harvesting systems. Flue‐cured cultivars ‘Coker 139’ and ‘NC 95’ and a pale yellow hybrid were used. These tobaccos varied in ripening patterns, total alkaloids, and reducing sugars. Harvest systems used were conventional, twice‐over, and once‐over for 61 cm and 115 to 140 cm (normal) topping heights. The time of topping was varied in the once‐over harvest systems.

All of the modified systems, except when the pale‐yellow hybrid was harvested twice, resulted in reduced yield compared to that of the conventional system. Yields were progressively reduced by the low‐topped treatments as the time of topping was delayed. Plants which were topped normally and had all of the leaves removed at one time produced the most undesirable tobacco; with NC 95 and the pale‐yellow hybrid being the poorest.

Total alkaloids were higher in tobacco from the low‐topped, once‐over harvest treatment (except that topped at harvest) than in that produced from the conventionally topped and harvested treatment. However, with a low‐alkaloid cultivar (Coker 139), an acceptable level of total alkaloids was obtained in the low‐topped, once‐over harvested tobacco when the plants were topped early. Cured leaf was produced from some of the low‐topped once‐over harvested treatments, that equalled that produced by conventionally topped and harvested for value per 45.4 kg, total alkaloids, and reducing sugars.
N Fertilization and Yield Response of High Lysine and Normal Barley1
Authors: Andersen A. J. , Køie B.
Published: July 2010

The yield and quality of barley (Hordeum vulgare L.) are greatly influenced by N fertilization. The yield of dry matter, mineral nutrients, and protein are generally increased but the concentration of the essential amino acid lysine in the protein is usually decreased by increasing the supply of N. However, the effect of N may vary between genotypes. The purpose of this study was to compare the response to N of a high‐lysine genotype to that of normal barley.

The high‐lysine Risø mutant 1508 and its parent variety ‘Bomi’ were grown in plastic pots containing 22 kg sandy loam (Gray‐Brown Podsolic soil). Nitrogen was supplied as NH4NO3 in amounts of: O, 1, 2, 3, 4, and 6 g N/pot.

The yield of dry matter increased with N fertilization up to 3 to 4 g N/pot after which it declined with additional N‐supply, while the yield of protein continued to increase. Lower grain yield of the mutant was almost entirely caused by a smaller grain size. The concentration of lysine in Bomi protein declined when protein production was increased by application of N fertilizer, whereas in the mutant it remained nearly constant. The high‐lysine character was thus enhanced when protein content in the grain was increased. The concentrations of P, Ca, and Mg were higher while that of K was lower in the grain of the mutant 1508 than in the grain of the parent variety Bomi.
Yield and Quality of Corn and Grain Sorghum Grain and Residues as Influenced by N Fertilization1
Authors: Perry L. J. , Olson R. A.
Published: July 2010

Crop residues of grain sorghum (Sorghum bicolor (L.) Moench) and corn (Zea mays L.) have attracted attention as an alternate economical forage resource for livestock utilization. There are little data available on agronomic production factors affecting yield and quality of crop residues. We evaluated the effect of rate and time of N fertilization on irrigated corn and grain sorghum grain and residue yields, grain N content, and forage quality of the residues.

During 1972 and 1973 irrigated corn and grain sorghum plots were fertilized with O, 90, 180 and 270 kg/ha of N as a 32% N solution at planting or sidedress with two P levels (O and 22 kg/ha) incorporated prior to planting. Grain and residue samples were analyzed for grain N content, and residue crude protein and in vitro dry matter digestibility (IVDMD).

Corn grain yields increased significantly with N applied at 90 and 180 kg/ha, while grain sorghum grain yields increased significantly only at the 90 kg/ha rate. Grain N content increased with N fertilization for both crops. Grain sorghum N content was generally equal to or greater than corn. Residue yields of both crops were increased significantly by 90 kg/ha with no further increase at the higher N rate. Corn grain/stover ratios increased with increasing N levels. Crude protein of grain sorghum residues was consistently higher than corn while IVDMD values were consistently lower in grain sorghum. Crude protein increased significantly in grain sorghum residue with each increasing N level while little increase occurred in corn.

We conclude that N rate and time of application does affect yield and quality of row crop residues. This would have an affect on supplementation of livestock grazing row crop residues.
Long‐term Residual Fertility and Current N‐P‐K Application Effects on Soybeans1
Authors: Boswell Fred C. , Anderson O. E.
Published: July 2010

Soybean (Glycine max L.) yield response to currently applied fertilizers, especially N, has been erratic while responses to residual P and K have been more consistent. This study was conducted to determine if residual N‐P‐K fertilizers applied over a period of years to other nonleguminous crops would influence soybean fertilizer requirements. Soybeans were planted on a Rarden sl soil (Typic Dystrochrept) where plots had received the same rates of P and K for 13 years. Previous N levels were 56 or 112 kg/ha, depending on the crop. Since legumes had not grown on the area for at least 16 years, significant responses to 56 kg/ha of N occurred each year at the high level of P and K. A greater yield response occurred from the P application than from K. The fertilizer × year interaction effects on yield was greatest for P as compared to N or K interactions when fitted to a regression model equation. The highest rates of N‐P‐K resulted in significantly larger soybean seed, better quality (seed index), and higher crude protein content than low N‐P‐K rates or control plots. Crude protein was inversely related to total oil content. Even though relatively high levels of P and K were applied to certain plots for 16 years and crop residues remained on the soil surface each year, high levels of extractable (double acid) P or K were not found in the soil.
Rate of Dry Matter Accumulation in Soybean Seeds with Varying Source‐Sink Ratios1
Authors: Egli D. B. , Leggett J. E.
Published: July 2010

The rate of accumulation of dry weight in the seed is one important process in yield production by grain crops. Information on factors influencing the seed growth rate are needed to help identify yield limiting processes. This study was undertaken to determine the effect of varying source‐sink ratios on the rate of dry matter accumulation in seed of soybeans (Glycine max (L.) Merr.). The varying source‐sink ratios were obtained by removing approximately 50% of the pods or 66% of the leaf area (two leaflets from each trifoliolate leaf) at the end of the flowering period. The study was conducted for 2 years in the field.

The pod removal treatment reduced pod number by 20% at maturity and resulted in an increase in weight/seed over the control near the end of the filling period in one of the years. Removal of two‐thirds of the leaf area reduced the weight per seed near the end of the filling period in both years of study. Pod weights of the pod removal treatments were generally heavier than the control and the pods from the leaf removal treatments were lighter than the control. Defoliation lowered the concentration of sugar in the stem sap compared with the control; but, pod removal increased the concentration of stem sugars only near the end of the filling period. The data are interpreted as suggesting that seed growth rates are not closely related to photosynthate production and that storage carbohydrates serve as a buffer between seed growth and photosynthate production.
A System and Program for Monitoring CO2 Concentration, Gradient, and Flux in an Agricultural Region1
Authors: Rosenberg Norman J. , Verma Shashi B.
Published: July 2010

Because of the changing global concentration of carbon dioxide and the possible effects of this change on photosynthetic activity worldwide, a program has been developed for monitoring atmospheric carbon dioxide concentration and gradients representative of a large agricultural region. The program is carried out at Mead, Neb. A meteorological tower is equipped with sampling intakes at various elevations up to 16 m, through which air is drawn to the laboratory for analysis with infra‐red gas analyzers. An automatic calibration system has been developed to permit hourly checks of analyzer performance. Profiles of wind speed and air temperature are also measured. The equipment, the calibration techniques, and the errors associated with the measurements of CO2 concentration and gradients are described. Some initial observations of CO2 concentrations and fluxes are presented.
Differential Response of Soybean Cultivars to Metribuzin1
Authors: Wax L. M. , Stoller E. W. , Bernard R. L.
Published: July 2010

Metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazin‐5(4H)one] controls several species of troublesome annual broadleaf weeds in soybeans [Glycine max (L.) Merr.] but it sometimes causes excessive crop injury. To determine the extent to which this injury is caused by differential sensitivity of cultivars to metribuzin, we evaluated the response of approximately 250 soybean cultivars to soil‐incorporated metribuzin in field experiments in 1973 and 1974. Most cultivars were relatively tolerant of metribuzin at 0.56 kg/ha. At 0.84 and 1.7 kg/ha, many entries were severely injured or killed. Some of the most sensitive cultivars were ‘Altona,’ ‘Hurrelbrink,’ ‘Norman,’ ‘Portage,’ ‘Semmes,’ ‘Tracy,’ and ‘Vansoy.’ These cultivars, and possibly others with only moderate resistance to metribuzin, should probably be avoided when metribuzin is to be used for weed control.
Effects of Concentrated Superphosphate and Potassium Chloride on Residual Available P, K, and Cl in Three Depths of Soil Derived From Calcareous Glacial Till1
Authors: Peck N. H. , MacDonald G. E. , Vittum M. T. , Lathwell D. J.
Published: July 2010

There is increasing concern by the general public about possible pollution of the environment resulting from applications of commercial fertilizers. This concern may conflict with the need to apply adequate, but not excessive, fertilizers to obtain optimum and economical production of crops. Thus a long‐term field experiment was designed to determine cumulative effects of applications of 0, 84, 336, and 1,344 kg concentrated superphosphate (CSP) and 0, 67, 268, and 1,072 kg potassium chloride (KCl)/ha on the uptake of P, K, and Cl by plants and on residual available soil P, K, and Cl. Applications of CSP and KCl were made nine times in 10 years to a Honeoye fine sandy loam (Glossoboric Hapludalf, fine loamy, mixed, mesic). Without fertilizer CSP and KCl, more P and K was taken up by vegetables and alfalfa than was measured as available by Morgan's extraction solution in the top 0 to 25 cm of soil. Applications of 84 kg CSP (17.5 kg P) and 268 KCl (140 kg K) per ha nearly equalled the average annual uptake of P and K by the plants over the 10‐year period. Residual available soil P accumulated in the top 0 to 25 cm of soil with the two highest rates of CSP, and available soil K accumulated with the highest rate of KCl. Downward movement of P, K, and Cl into the 24 to 43 cm and 43 to 61 cm depths of soil was measured by Morgan's and 1:1 (soil:water) extractions. In conclusion, P accumulated in the surface soil to a greater extent than K and Cl from fertilizers, while K and especially Cl moved downward in the soil more than P.
Components of Soybean Seed Yield as Influenced by Canopy Level and Interplant Competition1
Authors: Weil R. R. , Ohlrogge A. J.
Published: July 2010

Recent work with genetic manipulation of the shape of the canopy and investigations of the source‐sink relationships in soybeans [Glycine max (L.) Merr.] have emphasized the need for more information on hew various canopy levels and yield components contribute to the whole plant seed yield. A study was conducted to determine the vertical distribution of seed yields within the canopies of eight highly productive commercial soybean fields. Also, by thinning the stands to one plant/m2 at the beginning of the pod‐filling period, the effect of decreased interplant competition on weight/seed was studied independently from other seed‐yield components. Plants thus thinned yielded 12.5% more per node with 11.5% higher seed weights than the normal density plants.

The plant canopies were divided into five horizontal strata or canopy levels: canopy level 1 being the lowest 20% of the nodes, and so on. For the normal density plants, canopy levels 1, 2, 3, 4, and 5 contributed 19.51, 27.51, 26.51, 17.47, and 8.76% of the whole plant seed‐yields, respectively. The thinning treatment had its greatest effect at the top of the canopy, with progressively diminishing effects toward the bottom. Thus, in the uppermost canopy level the weight/seed was 23.9% greater on the thinned than on the unthinned plants, while weight/seed in the lowest canopy level was unchanged. This interaction between canopy level and plant density during the pod‐filling period may have been due to an alteration in the pattern of translocation and an inability of the lowest leaves to respond to increased light intensity.
Interaction Between Leaf Elongation, Photosynthesis, and Carbohydrate Levels of Water‐stressed Corn Seedlings1
Authors: Barlow E. W. R. , Boersma L.
Published: July 2010

Young rapidly expanding leaves of a corn (Zea mays L.) plant are major photosynthate sinks. Recent evidence indicates that expansion of these young leaves may be severely restricted for a considerable time during the diurnal light period by low leaf water potential and/or low soil temperature. To better understand effects on photosynthesis of prolonged diurnal reduction in leaf expansion, net photosynthetic rate of lower mature leaves, which act as a major source of photosynthate for young expanding leaves, was monitored under environmental conditions shown to restrict the expansion of the young leaves.

When leaf elongation was restricted by lowering root temperature from 27.5 C to 15.0 C, net photosynthetic rate of the source leaf was reduced 47% and soluble carbohydrate content of the sink leaf increased 45% at the end of a 7‐hour treatment period. Only about one‐third of this reduction in net photosynthesis was due to the concurrent decrease in leaf water potential. When leaf elongation was restricted by cooling the shoot apical meristem region from 27.5 C to 6.0 C, net photosynthetic rate of the source leaf decreased 24% and its soluble carbohydrate content increased 23% while the soluble carbohydrate content of the sink leaf increased 40% at the end of a 7‐hour treatment. These experiments support the hypothesis that environmental factors which limit leaf elongation may indirectly decrease photosynthetic potential of source leaves within the time limits of the diurnal stress cycle.
Mulch, Nitrogen, and Irrigation Effects on Growth, Yield, and Nutrient Uptake of Forage Corn1
Authors: Khera K. L. , Khera Romesh , Prihar S. S. , Sandhu B. S. , Sandhu K. S.
Published: July 2010

Nitrogen, irrigation, and soil‐temperature regime are major factors influencing crop growth. Hot season crops in tropical areas are reported to benefit fom soil temperature reductions caused by straw mulching. But how the mulch would affect the nitrogen and irrigation requirements of the crop is not known. We studied the independent and combined effects of two rates of straw mulch, viz., 0 and 6 metric tons/ha; three rates of nitrogen, viz., 50, 100, and 150 kg N/ha; and three levels of irrigation, viz., 7.5 cm irrigations based on irrgation water (IW)/pan‐evaporation (PAN‐E) ratios of 0.6, 0.9, and 1.2 on forage corn (Zea mays L.) in a 2‐year field experiment.

Green and dry forage yields and uptake of N and P significantly increased with mulching and with each successive increment of nitrogen. As the IW/PE ratio increased from 0.6 to 0.9 the green and dry forage yields and nutrient uptake increased significantly, but declined with further increase in irrigation. As a 2‐year average, mulching increased the dry forage yield by 11.8 quintals/ ha or 26% and showed a significant interaction with nitrogen rates. Fifty kg and 100 kg N/ha with mulch yielded as much as 100 kg and 150 kg N/ha without mulch, respectively.

It is indicated that straw mulching in forage corn during hot and dry season increases yield and nutrient uptake and helps economize nitrogen.
Cotton Population Dynamics: Influence of the Within‐the‐Row Spacing and Emergence Time1
Authors: Wanjura D. F. , Bilbro J. D.
Published: July 2010

Dynamic and stochastic properties of cotton (Gossypium hirsutum L.) plant populations increase the difficulty of production management. The influence of four within‐the‐row plant spacings on beds spaced at 102 cm (5, 20, and 40 cm, and random 7.5 to 10 cm) and three times of emergence (5, 7, and 9 days in 1973; 6, 8, and 10 days in 1974) on means and coefficient(s) of variability (CV) of plant height, number of main stem nodes, squares, and bolls were measured over time using the cultivar ‘Tamcot 788’. The CV values for each plant component varied with stage of development. The range of CV values was 16 to 31% for plant height, 14 to 23% for number of main stem nodes, 30 to 187% for number of squares, and 36 to 270% for number of bolls. Emergence time exerted a significant influence on the CV values of all plant characters throughout the 1973 season and during the first 80 days in 1974. Plant spacing significantly affected CV values of squares and bolls at first square and peak bloom in 1973. In 1974 plant height was affected beginning at 86 days after emergence; number of main stem nodes, after 100 days; and number of bolls, after 93 days.

Mean plant height and number of main stem nodes was greatest for early emerging plants. The highest number of bolls at maturity was produced on the earliest emerging plants in 1973. The 5‐cm plant spacing reduced the number of main stem nodes at maturity without affecting plant height in 1973. However, after midseason in 1974, plants spaced 5 cm were shorter and had fewer nodes than plants spaced 20 and 40 cm.

Plants experienced greater moisture stress in 1974 than in 1973. The CV values for plant height and main stem node number during 1974 for plants spaced at 5 cm increased as the season progressed, but did not change for plants spaced at 20 and 40 cm. CV values for main stem node number and plant height showed no seasonal trend in 1973.

Plant spacing and emergence time influenced the means and variabilities of plant components. The level of variability is different for each plant character and changes over time. An estimate of the true mean of a plant component over the season at the same confidence level would require adjustment of the sample size according to the variability changes.
Response of Oats to Water Deficit. II. Growth and Yield Characteristics1
Authors: Sandhu B. S. , Horton M. L.
Published: July 2010

Little information is available on the response of spring oats (Avena sativa L.) to periodic water deficits experienced at different growth stages. Knowledge concerning the manner in which oats responds to water stress is needed to aid in water management of the crop. The primary objective of this study was to determine the effect of a 9 to 11‐day water stress period imposed under a field environment upon the growth and yield components of spring oats (cultivar ‘Jaycee’). The crop was grown on pachic udic haploborolls soil (Lismore silty clay loam) in large pots buried in the field under a natural environment. The water stress periods were timed to occur during the boot stage and the anthesis through early grain formation stage (separately and in combination). Water stress at either stage decreased plant height and the number of florets per panicle. Plants stressed at anthesis through early grain formation had significantly more floret sterility and a fewer number of heads at maturity. Water deficits at all stages caused a marked decline in the yield of straw, tops without panicles, panicles, kernels, and dehulled kernels. Stress at the booting and the anthesis through grain filling depressed kernel yield 20% and 58%, respectively, whereas the combined stress reduced kernel yield 67%. Plants growing under soil water stress conditions appeared to root to a greater depth. On rewatering, the stressed plants, particularly those stressed in the boot stage, showed accelerated growth and profuse tillering. The results indicate that oats are more sensitive to soil water deficits which occur during the anthesis through early grain formation stage than during the boot stage. Therefore, cultural practices and water management should be so implemented to avoid soil water stress during the anthesis through early stage of grain formation.
Autumn‐Accumulated Tall Fescue and Orchardgrass. II. Effects of Leaf Death on Fiber Components and Quality Parameters1
Authors: Archer K. A. , Decker A. M.
Published: July 2010

The practice of accumulating late summer and fall forage growth for winter pastures is growing. As temperatures drop in the fall, and as growth rates decline, the percentage of dead leaf material increases. The effects of reduced growth rates, and increased leaf senescence, has a pronounced effect on the quality of accumulated forage. The objective of this research was to determine the relationship between dead leaf content and whole plant digestibility of autumn‐saved forage.

Field experiments were conducted during 1970–71 on a Beltsville silt loam soil (Typic Fragiudults) to determine the influence of N application and soil temperature on leaf deaths, fiber components, and quality parameters of autumn‐saved ‘Ky‐31’ tall fescue (Festuca arundinacea Schreb.) and ‘Potomac’ orchardgrass (Dactylis glomerata L.).

Nitrogen was applied at either 0, 50 (1970 only), or 100 kg N/ha in late September. In 1971, soil temperatures were maintained at ambient and aproximately 12, 20, and 27 C during the autumn using specially designed field equipment. Forage samples were collected from randomly‐selected, previously unharvested areas. These were separated into green and dead leaf fractions and analyzed for fiber components and quality parameters.

Neither forage species, N application, nor soil temperature greatly affected neutral detergent fiber, acid detergent fiber, lignin, or silica contents of autumn‐saved forages. However, there were trends for high fiber and lignin contents in plants grown on high soil temperature plots and for increased fiber content with time during autumn and early winter. Green leaves had lower levels of neutral and acid detergent fiber, lignin, and silica than dead leaves.

During autumn and early winter, the proportion of dead leaves in the pastures increased from approximately 20 to 46% in both years; IVDMD of the green leaf fraction decreased slightly during this period from 89 to 85%. In the dead leaf component, IVDMD remained at approximately 67% in 1970 but increased from 60 to 75% in 1971. Relationships were developed for both years which showed that IVDMD of the pastures decreased by 3.38% (r = −0.8477, P 0.001) and 1.0% (r= −0.3147, P 0.05), respectively, for each increase of 10% in dead leaf content.

The data indicate that caution should be exercised when using dead leaf percentages alone to predict forage quality of fall‐saved pasture; instability in the IVDMD of the dead leaves appears to be a major factor.
Influence of Temperature on Tall Fescue Forage Quality and Culm Base Carbohydrates1
Authors: Smith A. E.
Published: July 2010

Information concerning the influence of temperature on fescue (Festuca arundinacea Schreb.) forage production and quality is limited. Most of the reported research has been accomplished in swards and in controlled environment chambers for short time periods or for extended time periods with infrequent clipping. This study was designed to determine the long‐term influence of two controlled temperature regimes on: a) fescue forage production and quality and b) culm base carbohydrate concentration while being frequently harvested. Plants grown in the cool environment (20/10 C day/night temperature) produced 20% more herbage with a 7% higher average in vitro dry matter digestibility than plants maintained in the warm environment (30/20 C). Crude protein and foliage moisture percentage were not influenced by these temperatures. Foliage tissue from plants grown in the cool temperature contained twice as much sucrose and 88% more fructosans than plants grown in the warm environment. Culm base material from plants grown in the cool environment contained 37% higher total water soluble carbohydrates than the plants from the warm environment. This difference was primarily due to differences in the longer chain fructosans indicating that storage carbohydrate production occurs under temperatures favorable to increased forage production.
Control of Weeds in Narrow‐Row Soybeans1
Authors: Burnside O. C. , Moomaw R. S.
Published: July 2010

Improved weed control systems in the absence of row cultivation were researched in order to take advantage of higher yields of soybeans [Glycine max (L.) Merr.] grown in narrow rows. Weed control systems, utilizing 13 pre‐emergence and two postemergence herbicides or herbicide combinations and the rotary hoe, were devised for the production of narrow‐row soybeans at two locations in eastern Nebraska during 1972–74. Experiments were conducted on a Sharpsburg silty clay loam (Typic Argiudoll) at Lincoln and on a Judson clay loam (Cumulic Hapludoll) at Concord, Neb. Research was undertaken to reduce labor, energy, and production costs while attempting to achieve better weed control, earlier ground cover, and higher soybean yields. Selective control of grass weeds in soybeans was more readily accomplished than the control of such large‐seeded broadleaf weeds as Pennsylvania smartweed (Polygonum pensylvanicum L.), sunflower (Helianthus annuus L.), and valvetleaf (Abutilon theophrasti Medic.). Reduced application rates of grass herbicides were used successfully in narrow‐row soybeans. Weeds were controlled in soybeans, with a number of herbicide treatments, with only minor early crop injury and no stand reduction. Average weed yields from all herbicide treatments were markedly lower than those on weedy check plots, but were not significantly different from the hand‐weeded plots. All herbicide treatments except one produced average soybean yields that were equivalent to those on the hand‐weeded plots. Available weed control systems can eliminate the need for cultivation in narrow‐row soybean production. Such systems of weed control should increase soybean yields, reduce production costs, require less labor and fuel, and improve ground cover needed to protect our soil from wind and water erosion.
Effect of P, K, and Lime on Growth, Composition, and 32P Absorption by Merion Kentucky Bluegrass1
Authors: Watschke T. L. , Waddington D. V. , Wehner D. J. , Forth C. L.
Published: July 2010

Information is needed concerning the effects of different soil fertility levels on the activity of turfgrass roots in that part of the soil profile sampled for routine soil tests. In Pennsylvania, a sampling depth of 5 to 7.5 cm is suggested for established turf. A study was conducted on ‘Merion’ Kentucky bluegrass (Poa pratensis L.) to determine relationships among lime, phosphorus, and potassium applications; soil test results; foliar growth and elemental analysis; and root activity as determined by 32P uptake from three soil depths. In the field, soil pH values were 5.8 and 7.0, P ranged from 13 to 137 ppm, and K ranged from 0.14 to 0.43 meq./100g. Liming increased the Ca content in clippings from 0.35 to 0.42%. Phosphorus treatments increased P from 0.32 to 0.44%, and K was increased from 2.00 to 2.45% by K fertilization. Clipping yield was increased by P treatments. Sod plugs from the field were used in the greenhouse to determine root activity. Agar discs containing 32P were placed at a depth of 1.3, 3.8, or 6.4 cm, and clippings were assayed for 32P after 20 and 33 days. Shallow placement of 32P resulted in more absorption. A soil P × depth interaction was found for 32p absorption. A significant positive correlation between soil P and 32P absorption was obtained for the 1.3 cm depth, whereas a nonsignificant correlation was found for the 6.4 cm placement. Results indicated that P enhanced rooting, and the magnitude of absorption from the 1.3‐cm depth exemplified the need for P near the soil surface for optimum turf establishment.
Assessment of Four Techniques for Estimating Yield on Dryland Pastures1
Authors: Michalk D. L. , Herbert P. K.
Published: July 2010

Information is limited on the suitability of short‐cut methods of yield assessment in low density pastures in marginal environments. Since this information would be of value to researchers working in such environments, four short‐cut, double sampling techniques were compared with hand clipping to assess their usefulness in estimating yield in large‐scale experiments located on low density, lucerne‐based (Medicago sativa L.) pastures. The methods included the measurement of pasture height (Method 1); percentage ground cover (Method 2); and a combination of Methods 1 and 2 assessed either by calculating the product (HG) of the direct measurement of the parameters (Method 3); and by utilizing a plywood board dropped on the pasture the height measurement of which effectively integrates pasture height and cover into a single expression (Method 4). Percentage ground cover was not correlated with yield and was considered unsuitable for predicting yield in this type of pasture. Significant correlations were apparent between yield and the parameters of height, and a combination of height and cover. Sampling variation is discussed in relation to the use of these techniques. All techniques (excluding percentage ground cover) possessed sufficient sensitivity to distinguish yield differences in grazed lucerne pasture. The board technique, the most sensitive, required 53% less time than the others in data collection than clipping.
Non‐Destructive Leaf Area Estimation in Sunflower1
Authors: Schneiter A. A.
Published: July 2010

An accurate, easy rapid, non‐destructive method for leaf area determination in sunflower (Helianthus annuus L.) is needed. This study was designed to determine the feasibility of using different leaf parameters, or their combinations, to estimate leaf area. The study was conducted in the field with both oilseed and non‐oilseed sunflower which had been sown on Fargo clay (Vertic Haplaquolls). Plant material for leaf area determination was harvested and/or measured when 50% of the disc flowers had completed flowering. Comparisons between calculated and measured leaf area indicate the regression formula LA = {[(L−W)×.6683]−2.45}, which incorporates both leaf length and width is applicable for non‐destructive leaf area estimation of sunflowers. The formula can be utilized in sunflower grown under diverse environmental conditions.