bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of Two Cotton Genotypes to Five Equidistant Spacing Patterns1
Authors: Fowler J. L. , Ray L. L.
Published: July 2010

High population densities have been proposed as one way of achieving earlier maturity in cotton (Gossypium hirsutum L.) by increasing the potential number of early fruiting points. But competition among closely spaced plants may adversely affect initiation and set of fruit. Theoretically, competition can be reduced by improving the uniformity of plant distribution. A year field study was conducted to determine the morphological and agronomic reactions of cotton to intraspecific competition over a wide range of plant populations within equidistant spacing configurations. Response to equidistant plant spacing was studied using two genotypes of upland cotton (Gossypium hirsutum L.) with contrasting plant types and five population densities ranging from 38,750 to 620,000 plants/ha in patterns where distance between plants within the row equaled the distance between rows. Vegetative and fruiting components were measured and dry weight determinations were made after destructive fractionation at three harvest dates. Yield, earliness, and fiber quality data were accumulated from weekly harvests of mature bolls. As plant population increased, dry weight per unit land area of all plant components increased except vegetative branches, which decreased. Leaf area index and the number of nodes to the first fruiting branch also increased with higher populations. A smaller, more compact plant developed as plant density increased, which was indicated by reductions in plant height, stem diameter, and number of branches. Boll size, number of seed/boll, seed index, and lint index were all reduced as plant spacing decreased. Retention rate of fruiting forms was apparently much lower in the very high plant densities. Population levels of 79,000 and 155,000 plants/ha were earlier maturing and produced higher lint yield than population levels on either side of this range. These results generally agree with those of investigations of cotton spaced in 1‐m rows. There was no evidence that high population densities in equidistant spacing patterns improve earliness or yield.
Sugar Cane Growth in Response to Mulch and Fertilizer on Saline‐Alkali Subsoils1
Authors: Eavis B. W. , St. J. Cumberbatch E. R.
Published: July 2010

In many parts of the world where salinity or alkalinity limit crop yields, leaching is impracticable. In Barbados saline‐alkali subsoils remained unproductive 6 years after they were exposed during earth‐moving operations. The objective of this study was to devise agronomic techniques to restore these lands to sugar cane (Saccharum officinarum L.) production. The effects of mulching and N‐K fertilization were studied. Factorial field experiments in which bare plots and plots mulched with cut grass were treated with fertilizer at three rates (70:82, 208:247, 416: 495 kg NK/ha) were carried out at two locations (sandy clay and clay soil respectively). Sugar cane tillers and soil moisture contents were measured weekly, and root development fortnightly. After 9 months of growth bare plots failed to produce any marketable yield in contrast to mulched plots which gave up to 53 metric tons/ha (sandy clay) and 118 tons/ha (clay). There were no responses to fertilizer rate on bare land, but on mulched land 1.2 times (sandy clay) and 2.2 times (clay) more yield resulted from the high compared with the low fertilizer rate. Regression analysis indicated the importance of root development and nutrient uptake to tiller elongation rates in rainy periods. In drier intervening periods of slower shoot growth, soil moisture status was most important, mulched land having a volumetric moisture content 4% higher than bare land. Mulching reduced run‐off and increased rainfall preservation. The experiments show that growth and response to fertilizer on saline‐alkali soils depends on the soil physical environment. Mulching combined with adequate fertilizer application is a satisfactory reclamation procedure for saline‐alkali soils in the semi‐arid tropics.
Ammonium Effects on Nutrient Cation Absorption by Wheat1
Authors: Cox W. J. , Reisenauer H. M.
Published: July 2010

Additions of small amounts of NH1 to adequate‐NO3 culture have been shown to increase crop yield and total N content, and to decrease the plant's content of metal cations. The magnitudes of these effects can be appreciable. Accordingly, experiments were done to elucidate their mechanisms, and to evaluate their roles in crop production. Wheat (Triticum aestivum L. ‘INIA’) was grown in the greenhouse in dilute constant‐composition cultures that supplied, in factorial combination, three levels of NH4 with four levels of either K, Ca, Mg, Mn, or Zn. Intake of mineral cations increased with the concentration of the ion in solution and was decreased by added NH4. Ammonium had a greater effect on the intake of the divalent than of the monovalent cations. Among the divalent cations the magnitude of the NH4 effect varied in the order: Zn > Mn ≥ Mg > Ca. The reduced influx of multivalent cations from added NH4 is postulated to result from the NH4 induced reduction of the level of slowly diffusible organic anions within the root. This results in a smaller chelate sink, increased internal cation activity, and reduced net influx.
Hard Red and Durum Spring Wheat Responses to Seeding Date and NP‐Fertilization on Fallow1,2
Authors: Black A. L. , Siddoway F. H.
Published: July 2010

With recent development of high‐yielding semidwarf hard red (Triticum aestivum L.) and medium‐height durum (T. turgidum L.) spring wheats, information voids have been created in the management guidelines needed to obtain optimum production. Our objective was to determine if the two wheat types, planted at the same rate and seeding depth, would respond similarly to NP‐fertilization and to early, medium, and late seeding dates. The soil at both field sites was a Williams sandy loam (fine‐loamy, mixed, Typic Argiborolls). Although grain yields were nearly two times greater with 25.1‐cm rainfall at Culbertson than with 17.2 cm of rainfall at Outlook, the two speciesof wheat responded similarly to seeding dates and fertilization. Applying N and P, each at 45 kg/ha, significantly increased grain yields 30 to 60% at both sites. With adequate P‐fertilizer, ammonium nitrate and urea increased grain yields of both varieties similarly on all three seeding dates.

Based on the results of this study, both types of wheat responded positively to early seeding and NP‐fertilization, so there would be no need to prepare separate production and fertilizer management guidelines for each wheat species. Grain yield increases from NP‐fertilization were greater for both types of wheat for the early and medium seeding than for the late seeding date.
Influence of Soybean Seed Size and Position on the Rate and Duration of Filling1
Authors: Egli D. B. , Leggett J. E. , Wood J. M.
Published: July 2010

Information on factors influencing the rate and duration of seed growth is needed to understand completely yield production. This study was undertaken to determine the relationship of seed size and the timing of pod development to the rate and duration of seed growth in soybeans (Glycine max (L.) Merrill). Field studies were conducted for 2 years (1974‐75) on a Maury silt loam soil (Typic Paleudults) utilizing five cultivars of varying seed size: ‘Kanrich’, 234 mg/seed; ‘Williams’, 171 mg/seed; ‘Cutler 71’, 165 mg/seed; ‘Custer’, 129 mg/seed; and ‘Essex’, 114 mg/seed. Each year the rate of dry matter accumulation in the seed was measured on the first and the last pods to develop on each cultivar. Kanrich had the highest seed growth rate (7.96 mg seed−1 day−1); Essex the lowest rate (3.64 mg seed”1 day1), and the other cultivars had rates intermediate between Kanrich and Essex. Seed growth rates were relatively constant across the early and late pods. The duration of the effective filling period (EFP) was less for the late pods on the indeterminate cultivars (Kanrich, Williams, Cutler 71, and Custer), and this resulted in slightly smaller seed. There was no difference in the length of the EFP among the five cultivars used. Air temperatures during the filling period were lower in 1974 than in 1975, and the low temperatures were associated with low seed growth rates, a long EFP and large seed. These data suggest that the rate of seed growth is partially determined by the genetic makeup of the seed. The direct relationship between seed growth rates and seed size provides an explanation of the negative correlations frequently observed between seed size and the number of seed produced by the plant.
Relationship of Soybean Germination and Vigor Tests to Field Performance1
Authors: Johnson Richard R. , Wax Loyd M.
Published: July 2010

A number of soybean (Glycine max (L.) Merr.) seed vigor tests are available through seed testing laboratories for use by seed producers and farmers. In order to determine if these tests provide more information on field performance than the standard warm germination test, seed lots differing in quality were planted in different field environments at a constant seeding rate (350,000 seeds/ha) and evaluated for percent emergence, final stand at maturity, and grain yield. Several germination tests, including the warm germination test (also evaluated for percent strong seedlings and percent diseased seeds), cold test, accelerated aging test, and tetrazolium test were conducted by seed analysts and statistically correlated with field performance.

Experiments were conducted on Cisne silt loam (Mollic Albaqualf) at Brownstown, Ill. and Proctor silty clay loam (Typic Argiudoll) at Urbana, Ill. When the same seed lots were planted at different planting dates and locations, field performance differed markedly depending on seedbed conditions. Stress seedbed conditions were difficult to predict in advance. For example, at one location poorer emergence was observed with a warm, dry seedbed than with a cold, moist seedbed. A greater number of laboratory tests correlated with field emergence in favorable seedbed environments than in unfavorable environments. The cold test showed a consistent high correlation with field emergence and final stand. In general, reduction in yield was associated with a loss in stand. The cold test was the most effective germination test for identifying seed lots that would perform well in the field and should provide more assistance than the standard warm germination test in identifying problem seed lots.
Chemical Soil Conditioner Effects on Sand Soils and Turfgrass Growth1
Authors: McGuire E. , Carrow R. N. , Troll J.
Published: July 2010

In recent years new chemical soil conditioners have been utilized for agricultural purposes. However, limited information is available on their potential for improving the moisture and/or nutrient retentions of sand soils subjected to compaction under turfgrass conditions. Two bitumenous emulsions, five polyacrylamides (PAM), and one polyvinyl alcohol (PVA) were evaluated in a greenhouse experiment and/or two field studies. The greenhouse soils were a washed concrete sand and a mesic Entic Fragiorthod, while the field studies were on a constructed golf green utilizing an urban laid, flood plain sand. Recommended rates were applied by injection (greenhouse study) or mixing prior to turf establishment (field studies). The influence of these chemical soil conditioner treatments on soil physical properties, cation‐exchange capacity (CEC), and growth of ‘Manhattan’ perennial ryegrass (Lolium perenne L.) or ‘Penncross’ creeping bent, grass (Agrostis palustris Huds.) was determined. In the field studies compaction was applied periodically with a power roller. Hydrophilic bitumenous emulsion did not retain a hydrophilic nature but became hydrophobic, which decreased moisture retention by 12.5 to 30.0% by volume at 0.10 bar tension. Turf quality was decreased. Hydrophobic bitumen emulsion treatment resulted in similar responses. With minor exceptions PAM materials did not significantly affect the soil physical, CEC, or turf growth parameters in these studies, irrespective of molecular weight or presence of a cross‐linker. The PVA material also did not influence these parameters. Under conditions of these studies, where sand soils were subjected to compaction, chemical soil conditioners used did not benefically affect soil physical properties, CEC, or turfgrass growth. In some instances the influence was detrimental to turfgrass quality and growth.
Responses of Stomata and Water, Osmotic, and Turgor Potentials of Jojoba to Water and Salt Stress1
Authors: Adams J. A. , Bingham F. T. , Kaufmann M. R. , Hoffman G. J. , Yermanos D. M.
Published: July 2010

Jo]oba (Simmondsia chinensis (Link) Schneider) is desert shrub which can provide a much needed substitute for sperm whale oil. Because of the absence of soil‐plant‐water data for jojoba and the limited amount of such information for desert plants in general, selected plants were water‐ and salt‐stressed in greenhouse soil and sand culture experiments. Responses of leaf water, osmotic, and turgor potentials to stress and associated stomatal behavior were studied.

Leaf water potentials of well watered jojoba plants (measured with thermocouple psychrometers) averaged —20 bars in the daytime and were generally below —10 bars at night, very low in comparison to most mesophytic plants. The recovery of plants which were water stressed to leaf water potentials below —50 bars (soil water potentials below —40 bars) indicates great drought tolerance. Turgor potential decreased linearly with decreasing leaf water potential, showing a lack of osmotic adjustment as leaf water potentials fall below about —30 bars. Turgot potential reached zero at a leaf water potential of about —35 bars, and dropped as low as —10 bars under the most severe water stress without wilting of mature leaves. Plants in the salinity experiment showed osmotic adjustment down to a root medium osmotic potential of —9 bars.

Values of leaf conductance decreased markedly only at very low xylem pressure potentials (pressure chamber measurements) and soil water potentials (—40 bars and —20 bars, respectively), corresponding to about the same values at which turgor potential reached zero. Stomatal closure was continuous with increasing water stress, rather than occurring abruptly at a threshold. There was no significant decrease in leaf conductance at root medium osmotic potentials as low as —9 bars in the salinity experiment.

Conductances of well watered plants to water vapor on lower leaf surfaces were typically similar or greater in value than those of upper leaf surfaces, whereas plants under water stress showed significantly higher conductances on their upper leaf surfaces rather than lower leaf surfaces.

Leaf xylem pressure potentials decreased with increasing transpiration rate under non‐limiting soil water conditions and decreased below values predicted for well watered plants at the same transpiration rate as soil water potentials decreased. Thus it was possible to make an estimate of edaphic limitations of water absorption based on leaf xylem pressure potentials despite variation in the pressure potentials in response to microclimatic changes.
Radiation and Energy Balance of Sprinkler and Trickle Irrigated Fields1
Authors: Ben‐Asher J. , Fuchs M. , Goldberg D.
Published: July 2010

Water conservation claims in favor of trickle irrigation are poorly documented. The radiation and energy balance of tomatoes (Solanum lycopersicum L. ‘Arava S‐5’) grown on sand dune soil and on bare soil irrigated by sprinkling and trickling were compared. Under trickle irrigation, the average ratio of five energy balance measurements of evapotranspiration over evaporation pan (Class A) was 0.3, compared with 0.60 obtained under sprinkler irrigation. The comparison of radiation balance over the trickle and sprinkler irrigated plots indicates that the increased radiant heat loss and albedo from the dry portion of the trickle irrigated plot decreases the available evaporative energy at ground level. The smaller radiant heat load combines with the resistance of the dry soil to water flux to reduce the evaporation of the trickle irrigated plot.
Chemical Composition and Potential Uses of Annual Canarygrass1
Authors: Robinson Robert G.
Published: July 2010

Annual canarygrass (Phalaris canariensis L.) is used for birdfeed, but this research was undertaken to study its chemical composition and evaluate its potential for food or industrial uses. Caryopses and hulls were analyzed for elemental, amino acid, ash, oil, and fiber composition. Roots, stems, and florets were analyzed for elemental composition. Factors to convert N percentage to protein percentage were calculated by dividing 100 by the percentage N in the total amino acids of the caryopses, hulls, or florets. Mature plants from research plots in southeastern and northwestern Minnesota were analyzed by standard methods. Soils were Typic Hapludolls and Vertic Haplaquolls. Caryopses of ‘Alden’, ‘Heracles’, ‘M82’, ‘M89’, ‘M139’ and ‘P.I. 170622 Turkey’ were not markedly different in chemical composition. Canarygrass and oat (Avena saliva L.) differed significantly in elemental composition of florets but not in stem or root composition. Data averaged from 3 years and three locations showed that canarygrass Caryopses had a total amino acid concentration of 19.25% and a N to protein conversion factor of 6.71. The high amino acid concentration placed canarygrass above most grain crops and in a group with many pulse and oilseed crops. Its N‐to‐protein conversion factor was the highest reported for any crop. Canarygrass caryopses had higher concentrations of all eight essential amino acids than did those reported for wheat (Triticum aestivum L.) or corn (Zea mays L.) caryopses. Canarygrass hulls contained 20% ash. Annual canarygrass is a potential food grain crop.
Differential Response of Soybean Varieties to Soil Cadmium1
Authors: Boggess Sam F. , Willavize Susan , Koeppe D. E.
Published: July 2010

Of the trace elements being redistributed by our present‐day society, Cd presents probably the greatest potential as a toxic agent in applications to soils. Numerous studies have indicated that various plant species accumulate differing toxic amounts of Cd, and that the toxic symptoms are exhibited differently. Studies to assess the possibility that different varieties of one plant species may exhibit a range of Cd uptake and/or susceptibility have not been conducted in a comprehensive manner. This paper presents the results of a comprehensive survey of the Cd uptake and effect by a number of the prominent soybean [Glycine max (L.) Merrill] varieties grown on several CdCI2 or sewage sludge‐amended soils in the glasshouse. In all varieties, Cd toxicity symptoms appeared as a continuum from slight effects observed as a red, red‐brown, or purple coloration at the junction of the leaf blade and petiole, to severe leaf curling and extensive reddening of the leaf veins, chlorosis, and finally a brittle condition followed by abscission of the leaves. All varieties showed increased shoot Cd concentration and decreased dry weight in response to soil CdCl2, but varietal differences in the severity of these Cd effects were observed. To quantify these differences in plant response to soil CdCI2, indices based on the severity of visual symptoms, dry weight reduction, and shoot Cd concentration were used to rank the varieties according to Cd susceptibility. As all three rankings were significantly correlated, a composite susceptibility index based on all three criteria could be used to describe the response of each variety to Cd. Susceptibility index rankings of varieties grown on three different CdCl2‐amended soils were found to correlate with each other and with relative Cd concentrations of varieties grown on sewage sludge‐amended soil. Soybean maturity groupings were not correlated with visual symptoms, dry weight reduction, or shoot Cd concentration. The data suggest that of the soybean varieties tested for Cd susceptibility on CdCl2‐amended soils that Dunfield, Harosoy, Arksoy, Dare, Flambeau, and Scioto were generally the most susceptible while Clark, Mandarin, Mukden, Jackson, and Lee were consistently ranked as less susceptible.
Growth and Yield of Jojoba Plants in Native Stands Using Runoff‐Collecting Microcatchments1
Authors: Ehrler W. L. , Fink D. H. , Mitchell S. T.
Published: July 2010

Water‐harvesting techniques were applied to a waterstressed native stand of jojoba (Simmondsia chinensis (Link) Schneider) near Phoenix, Arizona, to evaluate this method of supplementing the normally scant rainfall for increasing seed yield and to gain insight into the comsumptive water requirements of the plant. Thirty small, indigenous, female bushes were selected and randomly divided into three treatments: T0, no water‐harvesting catchments; T1, cleared, smoothed, and rolled 20‐m2 catchments; and T2, like T1, but with the catchment treated with a water‐repellant coating. Data collected were: rainfall, runoff, soil moisture, relative leaf water content, plant volume, and seed yield. The 4‐year average of precipitation plus runoff to plants during the critical growth‐yield period of October through June was: T0, 154 mm; T1, 435 mm; and T2, 876 mm. The plant volume increase averaged 43, 44 and 237% for T0, T1 and T2, respectively. Seed yield in 1974, the first year, averaged 0.5, 8, and 23 g/plant for treatments T0, T1 and T2, respectively. Frost injury destroyed the flowers in 1975 and 1976, but in 1977 yields increased to 27, 76, and 208 g/plant for the respective treatments. Maximum yield was 514 g/plant. These preliminary results on this slow‐growing shrub suggest that its consumptive water requirement exceeds 450 mm, and may be as great as 900 mm. Water harvesting is one way of supplying this required water,
Interactions of Early‐ and Late‐planted Winter Wheat with Their Environment1
Authors: Thill D. C. , Witters R. E. , Papendick R. I.
Published: July 2010

In eastern Washington, early fall‐planted wheat (Triticum aestivum L.) has a greater yield potential than late‐planted wheat, and the additional fall growth of the early‐planted wheat improves erosion control after fallow. The purpose of this study was to investigate plant‐environmental interactions of early‐ and late‐planted wheat in the field and to determine morphological, physiological, and environmental interactions that contribute to the greater yield potential of the early‐planted winter wheat under disease‐free conditions.

Plant growth and development was evaluated on ‘Nugaines’ soft, white winter wheat planted in a Palouse fine silty soil (mesic pachic ultic Haploxerolls) in early September (EPW) and early October (LPW) in eastern Washington. Recommended rates of fertilizer for maximum yields were used and the wheat was sprayed with a fungicide in early spring to control Cercosporella foot rot. Canopy apparent photosynthesis and transpiration were measured throughout each day in the field by infraed gas analysis using an open system equipment design. Beginning in early spring, leaf area, number of tillers and heads, and plant dry weight were determined at 1‐ to 2‐week intervals. From these determinations, leaf area index and leaf area duration were calculated. In addition, leaf water potential and soil moisture depletion were measured throughout the growing season by use of a Scholander‐type pressure chamber and neutron moisture meter, respectively.

The EPW produced more grain field, tillers m−2, heads m−2, and kernal weight than the LPW, but significantly fewer kernels per head. Growth analysis indicated that EPW and the LPW plants maintained nearly equivalent internal plant water potentials throughout the growing season. Aparently, the EPW had superior yield potential because its root system was capable of extracting sufficient soil water during the spring and summer to maintain a plant water status that supported CO2 fixation per unit area of leaf equivalent to that of LPW. Thus, the maintenance of greater leaf area by the EPW during the grain‐filling period provided the basis for greater net assimilation and grain yield.
Molybdenum Availability as Predicted from Selected Soil Chemical Properties1
Authors: Karimian N. , Cox F. R.
Published: July 2010

Molybdenum deficiencies have been noted in the southeastern United States but there is limited information on plant and available soil Mo levels. Also, there has been little research directed toward interpreting these levels. Samples of 20 Coastal Plain and Piedmont soils were extracted with acid ammonium oxalate solution (Grigg Mo) and with anion exchange resin (resin Mo). Grigg Mo levels ranged from 17 to 183 μg/kg and resin from 2.5 to 11.1 μg/kg. Growth and uptake of Mo was determined on Early Snowball cauliflower (Brassica olera cea botrytis L.) grown in the soils which had been treated with none or 1 μg Mo/g soil. Soils from the Piedmont region without Mo produced cauliflower plants with Mo deficiency symptoms. Applied Mo increased dry weight and Mo concentration of cauliflower grown in most of the soils. No correlation was found, however, between response or plant Mo concentration and extractable Mo. The relative yield increases for applied Mo and plant Mo concentration could both be predicted reasonably well, though, from the active iron ratio (amorphous Fe/free Fe) and soil pH levels.
Thatch and Tiller Size as Influenced by Residue Management in Kentucky Bluegrass Seed Production1
Authors: Canode C. L. , Law A. G.
Published: July 2010

Kentucky bluegrass (Poa patensis L.) seed production is significantly greater when in situ post‐harvest residue burning is compared with mechanical removal of straw and stubble. The objectives of this research were to determine the amount of thatch accumulated for various methods of post‐harvest residue removed and to determine the influence of thatch on tiller size and panicle production.

Core samples from four cultivars of Kentucky bluegrass where residue had been open‐burned, machineburned, or removed were used for measurement of thatch and tiller size. Tillers were separated into three sizes according to base diameter, induced under field conditions, and grown in a glasshouse to force panicle production.

Mechanical removal of straw and stubble left 6.5 metric tons/ha of thatch after one seed crop and 10.1 and 15.2 metric tons/ha of thatch after three and four seed crops. Open burning and machine burning at high ternperatures reduced thatch accumulation about 50%. The total number of primary tillers and the number of large tillers was significantly greater following these treatments. Large tillers (2.0 mm) produced a high percentage of panicles, medium tillers (1.5 mm) produced few panicles, and small tillers (1.0 mm) produced essentially no panicles.

It was concluded that thatch reduction and the resulting production of a greater number of large tillers in the autumn was the primary response to post‐harvest residue burning that increased seed yield.
Interaction of Sodium Chloride and Temperature on Germination of Two Alfalfa Cultivars1
Authors: Stone J. E. , Marx D. B. , Dobrenz A. K.
Published: July 2010

Identification of laboratory conditions for isolating alfalfa (Medicago sativa L.) plants which tolerate high temperature and high saline soil during germination and stand establishment would be useful for alfalfa improvement in and and semi‐arid environments. An experiment was designed to determine the germination percentages of ‘U.C. Salton’ and ‘Ladak 65’ alfalfa cultivars at all combinations between sodium chloride osmotic potentials (OP) of 0 to −15 bars and temperatures of 21, 27, 33, and 39 C. U.C. Salton was developed for the low desert Southwest. Ladak 65 was developed for Montana. U.C. Salton showed slight enhancement of germination when the OP was lowered from 0 to −1 bar at 21,27, and 33 C. Ladak 65 showed this enhancement only at 27 C. At lower OP's, the germination percentages declined sharply for both cultivars. There was an interaction between the effects of temperature and OP on seed germination. Cultivar‐temperature and cultivar‐OP interactions were highly significant. A statistical model was established from these data. Quadratic response surfaces were found which had high degrees of fit to the data for each cultivar. The optimal temperature‐OP combinations for germination from the response surfaces were 25.4 C at −1.1 bar for U.C. Salton and 21.4 C at 0 bars for Ladak 65. Germination trends involving salt and temperature could be useful for establishing selection pressures in alfalfa improvement programs.
Contribution of Mycorrhizae to P Nutrition of Crops Growing on an Oxisol1
Authors: Yost R. S. , Fox R. L.
Published: July 2010

Most plant species, including the major crops, form symbiotic mycorrhizal associations between their roots and certain fungi which influence nutrient uptake, especially P, from infertile soils. How well‐supplied the phosphate must be before mycorrhizae cease to enhance P uptake is not known; nor have the effects of mycorrhizae on external P requirements of crops been adequately determined in the field. This study examined the influence of mycorrhizae on the P requirements of crops in a tropical field environment on a Tropeptic Eutrustox. Plant growth and P uptake by non‐mycorrhizal and mycorrhizal plants (methyl bromide‐fumigated and nonfumigated soil) were measured at 10 levels of soil P using seven plant species. Brassica chinensis, which does not form symbiotic mycorrhizal associations, consistently grew better and took up more P from the fumigated than from the non‐fumigated soil. All other species growing in nonfumigated plots formed associations with mycorrhizae. In general, plants growing on fumigated soil did not become infected with mycorrhizae. In P‐deficient situations, plant concentration of P was enhanced by the mycorrhizal associations. The levels of soil P at which fumigation ceased to make a difference in the P percentage in plants of the various species were as follows: Glycine max (L.) Merr. (0.1 µg P/ml), Vigna unguiculata L. (0.2 µg P/ml), Allium cepa L. (0.8 µg P/ml), Leucuenu leucocephala (1.6 µg P/ml), Stylosanthes hamata and Manihot esculenta (1.6 + µg P/ml). We suggest that this listing may be the order in which these species depend on mycorrhizae in P‐deficient soils. As a mean of six species growing on the two lowest soil P levels, P uptake by mycorrhizal plants was 25 times greater than by plants without mycorrhizal associations. Thus, some crops appear to be quite dependent upon a mycorrhizal association for P absorption from a soil of high sorption capacity.
Phosphorus Fertilization and Symbiotic Nitrogen Fixation in Common Bean
Authors: Graham P. H. , Rosas J. C.
Published: July 2010

Soils in the major bean (Phaseolus vulgaris L.) producing regions of Latin America are frequently deficient in both P and N. With the fertilizer available to small farmers limited, the appropriate strategy for efficient fertilizer use could depend on the relative P requirements for plant and nodule development and N fixation in this species. In this field study the objective was to examine the growth, P distribution, and parameters of N2 (C2H2) fixation of bean cultivars at different levels of P fertilization.

Seeds from 30 bean cultivars (replicates) were inoculated and lime pelleted, then sown into a Typic Dristandept soil low in available P. Phosphorus fertilization from 0 to 315 kg/ha as triple superphosphate was applied, then plant and nodule development, P distribution and N2 (C2H2) fixation measured 42 days after planting.

Nodules were a strong sink for P, nodule weight increasing ninefold and P concentration in nodules by almost 50% over the range of P fertilization used. Other plant tissues benefited less. Levels of N2 (C2H2) fixation , specific nodule activity, and non structural carbohydrate in nodules were highly correlated with supply of P.

Though P concentration in nodules reached 0.27%, there was no indication that the maximum fertilization rate used was adequate for full nodule development or nitrogen fixation. Further, none of the 30 cultivars tested showed reasonable N2 (C2H2) fixation at low rates of P fertilization. It may be concluded that identification of bean cultivars able to grow at low P, but still efficient in Na fixation, will be difficult.
Determination of Physiological Maturity in Oat1
Authors: Lee H. J. , McKee G. W. , Knievel D. P.
Published: July 2010

In studying various ecological and physiological factors affecting the yield of the several small grains, it is important to be able to define the length of the grain fill period, that is the period from anthesis to physiological maturity. Unfortunately, the various small grain crops do not develop a readily recognizable indicator, such as the ‘black layer’ in corn, Zea mays L., and tested methods to evaluate physiological maturity in small grains seem to be lacking. Our objective was to evaluate several techniques for determining when physiological maturity occurs in spring oat, Avena sativa L. In this study, five methods of determining physiological maturity were evaluated. Field grown plants of ‘Astro,’ ‘Noble,’ and ‘Otee’ spring oat were tagged when the spikelets at the second node from the base of the panicle were at anthesis. Plants were grown on a Murrill fine silty loam (a mixed, mesic Typic Hapludults.). Beginning 15 days after anthesis for each cultivar, spikelets at the tagged node were sampled daily, and an evaluation made of color changes in certain panicle parts, the uptake of a red, water‐soluble dye, and the uptake of14C‐sucrose. The groats were then weighed, freeze‐dried, and reweighed to secure dry weight and fresh moisture content. Lack of dry weight changes significant at p ⩽ 0.05 was used as the standard method to define physiological maturity and the other techniques compared to this. When half of the glume tips no longer took up the red dye and approximately 75% of the glume surface was yellow it provided a useful, nondestructive estimation of physiological maturity as defined by the dry weight method. Small amounts of 14C‐sucrose were taken up for a few additional days, but dry weight changes were not significant at p ⩽ 0.05. Groat and grain moisture content did not satisfactorily indicate physiological maturity. Observations of color changes in the glumes and cessation of dye uptake, either alone or in combination, provide a method of comparing the length of the oat fill period under various cultural and environmental conditions and for various genotypes.
Maize Yields and Soil Nutrient Levels With and Without Pesticides and Standard Commercial Fertilizers1
Authors: Lockeretz William , Shearer Georgia , Sweeney Susan , Kuepper George , Wanner Diane , Kohl Daniel H.
Published: July 2010

Because of increases in the price of chemical inputs to agriculture, uncertain supplies, and environmental concerns, a reduction in pesticide and fertilizer use may become increasingly desirable, if it could be achieved without a major reduction in output. For this reason, it is of interest to compare yields obtained under present conventional practice with those obtained at the lower limit of chemical intensiveness. This paper reports maize (Zea mays L.) yields on two groups each of 26 commercial mixed grain and livestock farms covering a wide range of soil types in the western Corn Belt. One group was managed with conventional fertilization and pest control practices, while no herbicides, insecticides, or standard commercial fertilizers were used on the other. The mean yield from the convenional fields was 8.5% higher than from the matched fields on which conventional fertilizers or pesticides were not used. The difference was not statistically significant (P<90%). Conventional maize yields tended to be higher than maize yields on fields which received no pesticides or fertilizers under favorable growing conditions and lower when conditions were adverse. Grain from the fields receiving pesticides and fertilizers had a significantly higher crude protein content. These fields also had a significantly higher incidence of Diplodia stalk rot and lodging. Soils from fields receiving no pesticides and fertilizers had a significantly higher (P>95%) organic C content, as well as higher total N (P>90%), but lower P1 phosphorus (P>90%). Differences in P2 phosphorus, exchangeable K, C:N ratio, CEC, and pH were not significant (P<90%)
Water Use by Wheat and Plant Indicators of Available Soil Water1
Authors: Meyer Wayne S. , Green George C.
Published: July 2010

This study was carried out during 1978 on the Highveld plateau of the Republic of South Africa to provide a more fundamental understanding of the water relations of wheat for irrigation management. The aim was to determine the amount of soil water extracted by wheat (Triticum aestivum L.) and to examine the response of leaf growth and predawn leaf water potential to a decline in soil water content. Evapotranspiration was measured with four weighing lysimeters which contained repacked profiles of the two soil types (Rhodic Paleustalf and Typic Ustropept) of the surrounding area. Three watering treatments were applied. One lysimeter was kept well‐watered by replenishing the deficit when 50% of the plant available water was depleted. The second treatment maintained the profile in a well‐watered state initially; thereafter no further water was applied while the plants dried the soil profile. The third treatment allowed the profile to be dried; a single irrigation was given and again the profile was dried.

Plants with well‐developed root systems extracted 80% of the plant available water at or near potential evapotranspiration rates. Plants with less well‐developed root systems extracted only 70% before a decline in the rate of water use was apparent.

Measurement of leaf and stem length during the drying cycle indicated that only 52 to 57%, of the plant available water was extracted before the plant growth rate in the drying treatment declined below that of plants which were well‐watered.

A rapid decrease in predawn or covered plant leaf water potential was evident around the time that the rate of water use began to decline. This indicated that the decline was primarily the result of a large resistance to water movement through the soil rather than a plant induced control.
Double Cropping Corn on the Coastal Plain of the Southeastern United States1
Authors: Widstrom N. W. , Young J. R.
Published: July 2010

The adoption of double‐cropping systems involving corn, Zea mays L., following corn in the same year would greatly improve the efficiency of land utilization in areas where the practice is possible. A study was conducted to determine if such a system would be useful in the southeastern U. S. where many locations have more than 240 frost‐free days during the growing season. Growing two crops during the same season would also help alleviate the feed‐grain deficit of states in the southeastern area. Our objectives were to determine which maturity Combinations could be expected to perform best and produce the greatest return when grown for grain or forage. We also wanted to determine whether there was an advantage in using hybrids with tropical germplasm for the summer crop. Two locally recommended hybrids and two hybrids containing exotic germplasm, each pair having one early‐maturing and one late‐maturing hybrid, were evaluated on the coastal plain of Georgia at Tifton in 1976 and 1977. The spring planting, consisting of the two recommended hybrids only, was harvested as grain; the summer planting, having all four hybrids, was harvested for grain and forage. The spring planting was effectively a 24‐replicate test to provide space for the six‐replicate summer planting which included all hybrid combinations. The experiments were planted as a split‐plot design, with the two hybrid adaptation types (exotic and recommended) providing the split, and maturity (late and early) combinations being randomized within each adaptation split. Early frost in 1976, hot weather in 1977, and an unusually heavy insect population during both years resulted in low grain yields for the summer planting each year. Overall performance levels were slightly better in 1976 than in 1977, but relative performance of the various hybrid and maturity combinations of the double‐cropping system was similar for both years.

Double cropping of corn might be a viable option on the coastal plain of the southeastern U. S. if the second crop were taken as forage rather than as grain. Grain yields of the summer crop were all less than 40 q/ha, and the early hybrids could not compete with late hybrids in forage production. Among maturity combinations, a recommended early hybrid, grown for grain as the spring crop, followed by late‐maturing hybrids, produced the highest ($957 to $1308/ha) average economic return. We suggest that some benefit may be obtained from using a hybrid with exotic (tropical or subtropical origin) germplasm for the summer crop and future testing of corn double‐cropping systems should include hybrids of this type.
Harvest Schedule, Persistence, Yield, and Quality Interactions Among Four Perennial Grasses1
Authors: Marten G. C. , Hovin A. W.
Published: July 2010

Comprehensive analysis of the interactions between harvest schedule and persistence, hay yield, and forage quality is lacking for cool‐season perennial grasses. Our objective was to determine whether harvest schedules typical of those producing a range from poor to excellent hay quality (two, three, or four times of cutting/year) under weed‐free conditions would differentially influence these properties for orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), reed canarygrass (Phalaris arundinacea L.), and smooth bromegrass (Bromus inermis Leyss.).

Three harvest schedules were used during the first 3 production years of this field experiment on Typic Hapludoll soil. In the 4th and 5th years, all plots were harvested three times to determine whether any adverse responses by the grasses to either more or less frequent harvest could be overcome.

Smooth bromegrass persisted poorest at the four‐cutting schedule, tall fescue and orchardgrass persisted poorest at the two‐cutting schedule, and reed canarygrass persisted best at all cutting schedules. Smooth bromegrass cut four times recovered substantially after the switch to three‐time harvest.

In vitro digestibility and crude protein concentration of reed canarygrass declined most rapidly, while those of orchardgrass or tall fescue declined least rapidly, due to maturation. The grasses did not differ greatly in rate of cell wall concentration increase. We obtained new evidence that crude protein concentration cannot be relied upon for assessment of generalized forage quality.

Reed canarygrass consistently yielded more dry matter than did smooth bromegrass, but otherwise frequent year‐to‐year yield variations existed among species and cutting schedules.

Our results show the necessity for imposition of several controlled harvest schedules over prolonged periods for accurate measurement of the potential of grasses intended for flexible forage management systems.
Floret Sterility in Rice in a Cool Environment1
Authors: Board J. E. , Peterson M. L. , Ng E.
Published: July 2010

Floret sterility induced by low temperatures of 15 C or below at meiosis (10 to 15 days before heading) is a major factor in reducing yields of Oryza sativa, var. japonica, L. in California. The objective of this study was to reduce Sterility by manipulating genotypic environmental interactions. Field experiments employing differences in plant height, maturity, and water level were conducted at the Davis Rice Research Facility. Microclimatic studies were also conducted to determine temperature profiles within the canopy. Sterility was compared among nine cultivars with similar genetic origin but differing in plant height and maturity. Those that were short‐statured and/ or early‐maturing exhibited significantly less sterility than tall and late cultivars. All cultivars in a water depth study showed less sterility in deep water (15 to 25 cm) than in shallow water (5 to 15 cm). Mean differences were significant at the 0.05 level. The beneficial effect of earliness in reducing sterility was caused by the weather patterns of the rice‐growing region in the Sacramento Valley. The probability of receiving temperatures below 15 C at meiosis was considerably reduced as maturity was shortened. Increased water depth and decreased plant height reduced sterility by placing the panicle in closer proximity to water. Field water temperature at the coldest part of the night was usually 5 to 6 C warmer than air temperature. The microclimatic study demonstrated that absence of substantial nocturnal wind caused a temperature inversion at night between the mid‐canopy level (50 cm above soil surface) and the top of the canopy. Temperature also increased from mid‐canopy to water level because of the warming effect of the water. Thus mid‐canopy is the coldest part of the vertical profile in a rice field.
Manure and Mineral Fertilizer Effects in Continuous and Rotational Crop Sequences in Central New York1
Authors: Baldock Jon O. , Musgrave Robert B.
Published: July 2010

Estimates of the effects of mineral fertilizer, manure, and legumes on crop yields and soil fertility in various technologies and environments are important for maintaining efficient crop production and reducing energy use in agriculture. Estimates of these effects were made in a long‐term study (1955 to 1968) at Aurora, N.Y. on soils of the Honeoye‐Lima and Kendaia series (Glossoboric Hapludalf and Aeric Haplaquept; fine loamy, mixed mesics; respectively). The crop sequences included continuous corn (Zea mays L.), wheat (Triticum aestivum L.), and grass and legume forage species, as well as several five‐phase rotations. The management treatments were manure (13.5 metric tons wet weight/ha/year averaged over the crop sequence), no manure, and different rates of N‐P‐K. The phases of each crop sequence were assigned to whole plots (0.0254 ha) in a randomized, complete‐block design (with six blocks or replicates), and the management treatments were assigned to the four sub‐plots.

Two years of alfalfa (Medicago sativa L.) apparently contributed 135 kg N/ha to subsequent crops. Manure apparently supplied 5‐1‐4 kg N‐P‐K per metric ton (wet weight). The amounts of N available from manure, alfalfa, and mineral fertilizer were additive, at least on corn. A common N response curve over all cropping systems fit the corn data well, which suggests that manure and crop rotation only affected corn yields through their plant nutrient contributions. Soil organic matter and pH were maintained and extractable soil P and K were increased over the 14 years of the study in both continuous and rotational cropping systems (with or without manure). The results suggest that on these soils, the plant nutrient requirements of field crops can be completely supplied by legumes and manure, by mineral fertilizer, or by some combination of them without leading to decreases in soil fertility.