bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake of N by Grass from Septic Fields in Three Soils1
Authors: Brown K. W. , Thomas J. C.
Published: July 2010

The N component of septic tank effluent could increase the concentration of nitrate in the groundwater. This study was conducted to determine the ability of vegetation to take up N from the soil surrounding septic lines, to minimize the movement of N to the groundwater. Six replications of three soils were enclosed in large undisturbed monolith lysimeters each containing a septic line. The soils had percolation rates of 25.4, 3.8, and <0.3 cm per hour and represented the range of those generally used for septic tank effluent disposal. The N content of the effluent was measured weekly and applications of effluent were made daily at rates based on the percolation tests. Common Bermudagrass (Cynodon dactylon L.) was harvested on three occasions representing a period of 1 year. Harvesting was done in strips above and adjacent to the field to determine the horizontal distribution of uptake. Grass uptake was equivalent to 9%, 32%, and 46% of the N applied to the soils which had percolation rates of 25.4, 3.8, and <0.3 cm/hour. Thus, the percent uptake was inversely related to the amount of N applied per unit area. The largest fraction was taken up from the soil which received the least amount of effluent. Uptake decreased rapidly with distance from the septic line, such that at a distance of 60 cm from the edge of the line the uptake approached that from the unfertilized native soil. These results indicate the possibility of utilizing vegetation to remove some of the N applied to septic fields, particularly from large fields which are installed in slowly permeable soils. It is suggested that physical removal of the grass would be necessary to achieve the desired effect.
Seed Size and Seeding Rate Effects upon Stand Density and Yield of Alfalfa1
Authors: Cooper C. S. , Ditterline R. L. , Welty L. E.
Published: July 2010

Legume seedlings from seed of different sizes compete with one another in pure seedings, usually to the detriment of smaller seedlings. We seeded variable rates of sized‐seed at Bozeman, Mont., to determine if less competition would permit lowering the seeding rate of alfalfa. We screened alfalfa (Medicago sativa L.) seed to small, medium, and large sizes weighing 160, 210, and 256 mg/100 seed respectively, and also made up a composite of the three sizes. We planted seed of each size at seeding rates of 1.1, 2.2, 4.5, and 9.0 kg/ha into a Bozeman silt loam (Agric‐Pachic Cryoboroll) soil in the field and measured seedling emergence and survival and yield in the year following seeding. Number of seedlings that emerged and number of plants that survived the second year were closely related to seeding rate. Percentage of planted seeds, resulting in mature plants from two separate plantings, decreased with increased seeding rate due to more intraplant competition. More seedlings emerged from small seed, or from the seed composite of all sized‐seeds, than from medium or large seeds. Seed size did not affect yield in the year of seeding or the year following. A seeding rate as low as 1.1 kg/ha at one location and 2.2 kg/ha at a second location gave maximum yield in the year following seeding.

Our data showed no advantage of sizing seed. Seedling density was as good or better with small or composited seed as with large seed at the same seeding rate.
Seasonal Trends of in vitro Dry Matter Digestibility of N‐Fertilized Bermudagrass and of Orchardgrass‐Ladino Pastures1
Authors: Fribourg H. A. , Barth K. M. , McLaren J. B. , Carver L. A. , Connell J. T. , Bryan J. M.
Published: July 2010

Improved cultivars of warm‐season grasses, such as ‘Midland’ bermudagrass [Cynodon dactylon (L.) Pers.] can produce much forage during the summer. However, weight gains by growing beef animals grazing Midland pastures, even when these are well‐managed, may be unsatisfactory in some months. In this study, the quality of grazable forage available to yearling beef steers, was measured at frequent intervals by in vitro dry matter digestibility (IVDMD).

Pastures of ‘Midland’ bermudagrass grown at four levels of N fertilization (0, 112, 224, 448 kg N/ha/year in three equal applications) were grazed by yearling beef steers and compared to common bermudagrass (C. dactylon var. dactylon) fertilized with 112 kg N/ha/year in three equal applications, and to a mixture of orchardgrass (Dactylis glomerata L.) and ladino clover (Trifolium repens L.).

The IVDMD of forage samples obtained at 2‐week intervals from mid‐April to mid‐September was determined for 3 consecutive years. The data were reduced to polynomial equations describing the regression of IVDMD on elapsed days of grazing. These equations were used to generate predicted IVDMD for a 160‐day grazing Season. Fertilization with N increased the seasonal mean IVDMD of Midland, but only the IVDMD of Midland‐448 was significantly greater than that of Midland‐0. Significant decreases in IVDMD from April to September were observed in each treatment (50.8 to 37.7, 54.3 to 33.7, 56.6 to 34.2, 57.1 to 34.9, 49.8 to 40.2, and 69.2 to 58.3% for Midland‐0, −112, −224, −448, Common‐112, and 0rc.‐Lad., respectively).
Sodium, Potassium, and Zinc Relationship in Corn1
Authors: Shukla U. C. , Mukhi A. K.
Published: July 2010

The relationships among Na, K, and Zn in corn (Zea ma,s L.) nutrition are not well understood. A greenhouse experiment was conducted by growing corn (‘Vijay’) for 45 days as an indicator crop. Treatments were Na (0, 50, and 250 ppm), K (0, 50, and 250 ppm), and Zn (0, 5, and 10 ppm) applied in all possible combinations, and replicated three ames. Sodium decreased shoot dry matter yield K, and Ca concentration, and increased Na concentration. Magnesium and Zn concentrations were not influenced by Na when Zn was applied. Potassium generally reduced the effectiveness of Na and Zn treatments, increased K concentrations, and decreasd Ca, Mg, and Na concentration. Zinc decreased the effectiveness of K and Na treatments, and increased yield, and Zn, K, and Mg concentration. At low levels of K, application of 10 ppm and Zn decreased Na and Ca concentration. A triangular relationship was evident among Na, K, and Zn, depressing each others effectiveness on growth and tissue concentrations. The adverse effect of Na on plant growth was attributed to its antagonistic relationship with Ca, K, and Zn in plants and increased salinity and alkalinity hazards in the soil.
Nitrogen Balance in Urine‐affected Areas of a New Zealand Pasture1
Authors: Ball Roger , Keeney D. R. , Thoebald P. W. , Nes P.
Published: July 2010

The high rates of urine‐N deposited during grazing offers the potential for considerable N loss through volatilization, leaching, and denitrification. A field experiment was conducted to evaluate the magnitude and pathways of N transformations and losses under warm, moist conditions. Urine was applied to 3‐m2 plots in a ryegrass (Lolium perenne L.)‐white clover (Trifolium repens L.) pasture at 300 or 600 kg N/ha. These rates simulate the urine affected area of sheep and cattle, respectively. Ammonia volatilization, inorganic N in the soil profile, symbiotic nitrogen fixation (by acetylene reduction assay), and herbage N yields were measured over 53 days. Four days after application from 30 to 35% of the added N could not & accounted for as either soil mineral N or volatilized NH3‐N. Ammonia‐N evolution was rapid only for the first 2 days, and I5 to 18% of the N was volatilized as NH3. Profile NH4‐N was completely nitrified by 21 days. Considerable amounts of the applied N was lost from the 0 to 45 cm profile by 53 days. Since rainfall and irrigation exceeded estimated evapotranspiration, leaching of NO3‐N is the probable loss mechanism. The apparent recovery of N in herbage was 37 and 22% of that added. Acetylene reduction was substantially less in the urine‐treated swards. From 30 to 35% of the urine‐N was not accounted for as inorganic N early in the experiment; immobilization and rapid leaching of urine below 45 cm are probable loss mechanisms. The experiment indicated that in a warm, moist environment, typical of late spring‐early summer in New Zealand, more than half of the N in urine voided by sheep or cattle can be lost, and that an intensively grazed grass‐legume system is far from a closed system, or cycle, with respect to N.
Interpretation of Foliar Analyses for Diagnostic Purposes1
Authors: Sumner M. E.
Published: July 2010

The precision and flexibility of various foliar techniques in making valid diagnoses of mineral imbalances in plants have seldom been critically evaluated. This paper compares the classical critical value approach with the newer Diagnosis and Recommendation Integrated System (DRIS) in evaluating diagnoses from the same sets of data. The critical value and sufficiency range norms for various crops are presented and from these, DRIS indices are calculated for comparative purposes. Although the norms for both approaches depart from essentially similar reference points, the DRIS approach is able to make diagnoses meaningfully over a range of plant ages and can classify the order in which nutrients limit yield. Comparisons of diagnostic precision between the two systems are made using data from various field experiments with corn, (Zea mays L.), soybeans (Glycine max L.), sugarcane (Saccharum officinarum L.), and potatoes (Solanum tuberosum L.). These comparisons are achieved by comparing yields on treatments with and without a particular nutrient which has been diagnosed as being limiting. A yield increase when the particular nutrient is applied indicates that the diagnosis was correct and vice versa, Overall, DRIS is superior to the critical value approach in that it is able to make valid diagnoses more frequently because variations due to tissue age are taken into account.
Influence of Slope Position on Nitrogen Fixation and Yield of Dry Peas1
Authors: Mahler R. L. , Bezdicek D. F. , Witters R. E.
Published: July 2010

Slope position and aspect are known to influence soil temperature and moisture which have a direct bearing on yield of agronomic crops. The objectives of this study were to determine the influence of soil slope on yield and N2 fixation by dry peas (Pisum sativum L.) in the field and to determine the effectiveness of isolates of Rhizobium leguminosarum taken from various slopes on N2 fixation by peas in the greenhouse. From N2(C2H2)‐fixation rates conducted weekly in three positions of a Palouse catena; bottomland (Xeric Argialbolls) south slope, (Ultic Argixerolls), and ridgetop (Pachic Haploxerolls), total seasonal N2(C2H2) fixed was estimated at 69, 22, and 17 kg/ha of N, respectively. For peas growing on the bottomland, south slope and ridgetop, plant N uptake was 210, 99, and 75 kg/ha of N, respectively. Pea seed yields of 2,106, and 480 kg/ha on the bottomland and ridgetop, respectively, were related to the amount of water depleted in the soil profile of 21.6 and 8.9 cm, respectively. Higher yield and greater N2 fixation by peas growing on the bottom slope were apparently related to greater root penetration and removal of water.

Greater plant N and dry matter were obtained in the greenhouse when peas were inoculated with isolates from the north slope when compared with isolates from other slopes. No differences were noted in pea growth and N2 fixation between isolates from the bottomland, south slope and ridgetop, which suggested that differences in N2 fixation and yield observed in the field were not related to efficiency of the microsymbiot
Sulfur Nutrition of Rice. II. Effect of Source and Rate of S on Growth and Yield Under Flooded Conditions
Authors: Blair Graeme J. , Momuat E. O. , Mamaril C. P.
Published: July 2010

Sulfur deficiencies are widespread in South Sulawesi, Indonesia, and responses to S have been recorded in rice, corn, and pastures in various parts of the province. The major fertilizers used in Indonesia are urea and triple superphosphate (TSP) and the continued use of these matenals has led to declining rice yields in some areas.

Field experiments were conducted at three sites in South Sulawesi to study the effect of S source (gypsum, ammonium sulfate, elemental S) and rate (0 to 80 kg S/ha) on grain production in flooded rice.

Sulfur deficiency in rice results in a marked reduction in tiller numbers. At one site panicle number was reduced from 14.9 per hill where 80 kg S/ha was applied down to 4.1 per hill in the S0 treatment.

Yield responses to S were recorded at all three sites and gypsum, ammonium sulfate and elemental S were equally effective in increasing yield when applied at transplanting. Elemental S applied 20 days before transplanting was less effective than elemental S applied at transplanting.
Rooting Depth of Kentucky Bluegrass Sod as Measured by N Absorption1
Authors: Peterson L. A. , Newman R. C. , Smith Dale
Published: July 2010

Bluegrass (Poa patensis L.) is used widely in temperate areas to establish a turf, and a large proportion is started from sod. Data on rate and extent of Bluegrass root development after sodding are not available; therefore, this research was initiated to study the depth of root development from pure Kentucky bluegrass for an extended period after sodding. In a field study on a Plano silt loam (Typic Arguidoll), nine plastic bags each containing 227 g of NH4NO3, (33‐0‐0) were placed uniformly in a m2 area at different soil depths before sodding. Soil placement depths of the N bags were 7.5, 15, 22.5, 30, 37.5, and 45 cm. Each bag contained eight pinholes for slow release for N over an extended period. Root activity was associated with N uptake from the different soil depths. Bluegrass roots penetrated to 7.5 and 15 cm shortly after sodding and developed to 30, 37.5, and 45 cm by the third, fourth, and fifth growing seasons, respectively. It is concluded that bluegrass roots are actively absorbing nutrients to a much greater soil depth than previously reported and that the root system in relation to soil depth becomes more extensive with time.
Harvest Index of Corn Affected by Population Density, Maturity Rating, and Environment1
Authors: DeLougherty Richard L. , Crookston R. Kent
Published: July 2010

Harvest index (HI) is one of the indices currently used to evaluate a crop's partitioning efficiency. The objective of this study was to determine how the HI of fieldgrown corn (Zea mays L.) was affected by changes in population density and relative maturity (RM) of hybrids. Plots were established at three locations. Ten hybrids (two from each of five RM groups) were grown at five population densities at each location. The Minnesota maturity groups represented were 75, 90, 105, 120, and 135 RM. Populations were 12.5, 25, 50, 100, and 200 thousand plants/ha. Substantially different environments (drought vs. normal) developed among the locations during the study. This provided an opportunity to also observe the effect of environment on HI.

The adapted hybrids (105 RM) planted at a normal production density (50,000 plants/ha) had an average HI of 0.39 (range = 0.32 to 0.47) over all environments. At each location, the maximum HI value was 0.50. As plants encountered increasing stress, they partitioned less and less dry matter into grain, eventually producing only stover.

Increasing population density resulted in significant decreases in HI at all locations. Differences in RM did not consistently affect HI, although the latest maturing hybrids did have decreased indices. The HI of corn appeared to be affected more by environment than by either population density or relative maturity. Harvest index and grain yield exhibited high positive correlations in the stress environment (r = 0.96), but were weakly correlated in the nonstress environment (r = 0.28). Also, harvest indices obtained in one environment had no predictable relationship to grain yields in a different environment. We thus conclude that population density, and especially environment, must be taken into consideration when evaluating HI information.
Effect of Nitrapyrin on Nitrification of Broadcast‐applied Urea, Plant Nutrient Concentrations, and Corn Yield1
Authors: Touchton J. T. , Hoeft R. G. , Welch L. F.
Published: July 2010

The use of nitrification inhibitors offers a method for decreasing initial nitrification rates and subsequently decreasing nitrate losses from soil. Thus, the use of inhibitors should increase N uptake and corn (Zea mays L.) yield in years when soil moisture conditions favor N losses. This study was conducted to evaluate the effects of nitrapyrin applied with broadcast applications of urea on nitrification, plant nutrient concentrations, and corn yield. Urea (0 to 268 kg/ha N) and nitrapyrin (0 and 2.24 kg/ha) were applied to a somewhat poorly drained soil (Flanagan silt loam ‐ Typic Hapludoll) in the spring and fall of 1975 and spring of 1976. Soils were sampled to a depth of 45 cm and plant tissue samples were taken at first silk and at physiological maturity.

Nitrapyrin was effective in decreasing nitrification rate of both fall‐ and spring‐applied N. Fall‐applied N without nitrapyrin was nitrified by mid‐March, but when nitrapyrin was added an average of 12% of the added N was recovered as ammonium from the top 15 cm of the soil in early June. More ammonium‐N was recovered from the soil in early June when N was applied in the fall with nitrapyrin than in the spring without nitrapyrin. While nitrate accumulations were found at a depth of 45 cm when urea without nitrapyrin was applied in the fall, nitrate did not accumulate below the 15‐cm depth when urea was applied in the fall with nitrapyrin or in the spring with or without nitrapyrin. Nitrapyrin did not affect the concentration of P, K, Ca, Mg, Cu, B, and Mn in the ear leaf, grain, or stover, but increased the concentration of Fe in the ear leaf by 10%. Nitrapyrin added with 67 kg/ha fall‐applied N increased concentration of N in the ear leaf by 15%. When applied with spring‐N, nitrapyrin increased the spring‐N concentration in the stover and grain by 13 and 17%, respectively. Nitrapyrin applied with 134 kg/ha spring N increased the N concentration in the ear leaf by 14'% but decreased the concentration in the grain by 11%. Nitrapyrin increased grain yield by 27% when applied with 67 kg/ha fall‐N, but decreased yield by 70%, when applied with 134 kg/ha spring‐N.
Plowing Effect on Corn Yield Response to N Following Alfalfa1
Authors: Triplett G. B. , Haghiri F. , Van Doren D. M.
Published: July 2010

Meadow crops traditionally are destroyed and incorporated into the soil for grain crop production by moldboard plowing. With no‐tillage crop production, vegetation is destroyed with herbicides and remains physically undisturbed. Such changes in management practices could influence release of nitrogen to the grain crop that follows. An experiment was designed to evaluate the response of corn grown for grain to N fertilizer rates under plowed and non‐tilled conditions on a Wooster silt loam, a fine‐loamy, mixed, mesic typic Fragiudalf soil. Nitrogen at rates of 0, 28, 56, 112, and 168 kg/ha was applied to corn (Zea mays I,.) following an alfalfa (Medicago sativa L.) meadow and planted with either no‐tillage or into soil that was moldboard plowed. In a field experiment of 3‐year duration, corn yield was increased by added N only in 1 year at the 56 kg/ha N level. No interaction of tillage and N rate occurred, indicating tillage was not necessary to release N contained in the legume crop. During one growing season with adequate amounts of rainfall, corn yields greater than 90 quintals/ha were produced without added N. Meadows containing an excellent stand of legumes are capable of supplying most, if not all, of the N needs for the grain crop that follows. This was true for rotation studies reported in the 1930's and 1940's when corn yields of 40 to 60 quintals/ha were common and seems to be true today when yield levels are almost double.
Root Characteristics of Corn Genotypes as Related to P Uptake1
Authors: Schenk M. K. , Barber S. A.
Published: July 2010

Plant utilization of P applied to soils is usually low. Utilization may be increased by having more roots present or by improving P uptake characteristics of the roots. The objective of this research was to determine the effect of varying corn (Zea mays L.) root characteristics, by using different genotypes, on P uptake and to determine if the Claassen‐Barber simulation model predicted these differences accurately. Five corn genotypes were grown in the growth chamber in soil at two levels of P and harvested a three ages. Increasing P level increased shoot yield of all genotypes, but had little effect on the amount of roots. The root surface area per unit of shoot weight varied between genotypes at low soil P but not at high soil P. Wih high soil P here was a linear correlation with r = 0.98 and a slope of 0.97 between P uptake predicted by the simulation model and observed P uptake. At low soil P observed P uptake was double the predicted uptake, however, the correlation was r = 0.90. Root hair effects, not included in the simulation model, were probably the reason for the greater observed P uptake at low soil P. Differences between genotype in morphological and physiological root characteristics in. fluenced the amount of P absorbed by corn plants. It appears that genotypes could be developed that would be more efficient in absorbing P from soil.
Effects and Treatments of Petroleum Spills on Bermudagrass Turf1
Authors: Johns D. , Beard J. B.
Published: July 2010

Due to the frequency of petroleum spill damage to turfgrass areas, a field study was conducted on ‘Tifgreen’ bermudagrass (Cynodon L. spp.) to determine the injury symptoms and subsequent recovery rates from petroleum spill damage. Five petroleum products commonly used in turfgrass maintenance equipment were applied as spill treatments to the turf growing on Lufkin fine sandy loam (fine, montmorillonitic, thermic, Vertic Albaqualf). Injury symptoms of the turf were documented following the three replicate spray applications of gasoline, motor oil, hydraulic fluid, and brake fluid, and following direct spreading of grease over 1 m2 plots. Calcined clay fines, activated charcoal, and detergent were evaluated as potential corrective treatments. Each corrective treatment was applied within 20 minutes of each spill in three replications.

The injury symptom varied among the petroleum spill treatments. Detergent proved effective in enhancing bermudagrass recovery (3 to 4 weeks) from motor oil, hydraulic fluid, and brake fluid damage. None of the corrective treatments were effective on either the gasoline or grease‐damaged turf. The bermudagrass recovered rapidly (3 to 4 weeks) from gasoline spills without corrective procedures. More than 10 weeks were required for recovery from grease spills.
Fertilizer Management with Drip Irrigation in an Oxisol1
Authors: Keng J. C. W. , Scott T. W. , Lugo‐Lopez M. A.
Published: July 2010

Oxisols are the dominant soils of the continental shields in the tropics under permanently moist and alternately wet and dry climates. Oxisols have a low cation exchange capacity, high permeability, but low available waterholding capacity. Some have a low pH, which can cause Al3* toxicity to many crops. Together with erratic rainfall patterns, special management methods of soil‐water and plant nutrients for Oxisols are yet to be carefully studied. The relatively recent development of combined high frequency irrigation and fertilizer techniques, “drip fertilization,” may be one of the solutions for intensive production of food crops on Oxisols.

A drip irrigation system using porous plastic tubing was designed for a field experiment to study the feasibility and operational techniques of drip irrigation and fertilization management in a highly weathered, acid Oxisol (Coto clay). Green pepper (Capsicum annuum L.), ‘Blanco del Pais’ was the test crop. A randomized, completeblock design was chosen to compare different fertilization techniques. In addition to the check plot, the three other treatments were: fertigation (drip irrigation and drip application of N and K, banded P); drip irrigation with banded N, P, and K; and drip irrigation with broadcast N, P, and K. All treatments, except the control plot, received a total amount of fertilizer equal to 56.8 g of 10‐10‐10 commercially available fertilizer per plant and all treatments were uniformly drip irrigated according to pan evaporation data.

Different moisture profiles during the wet (June‐November) and dry (December‐May) seasons were observed. Nutrient movement profiles suggested that the distribution of fertilizer under drip irrigation depended on the method of fertilizer placement. Root development patterns indicated that more than half of the root system (dry weight) was developed in the 5 to 15 cm layer. More fibrous roots were developed toward the porous drip tubing which supplied moisture and nutrients. Yield were significantly different among all treatments during the dry season and the fertigation, broadcast, and control during the wet season. Yields from broadcast fertilizer treatments were 15.8% lower than from fertigation, and 12.3% lower than from banded fertilizer. The results of this research indicates drip fertigation can be a promising alternative to currently used water‐nutrient management methods for Oxisols in the wet‐dry tropics.
Nitrogen Fertilization and Mowing Height Effects on Tensile Strength of Bermudagrass Sod1
Authors: Mitchell C. H. , Dickens Ray
Published: July 2010

The influence of N fertilization practices and mowing management on sod formation is of interest because both are important economic inputs in commercial sod production. Field experiments were conducted to determine the effects of mowing height, rate, and frequency of N applications on the sod tensile strength of ‘Tifway’ and ‘Tifgreen’ bermudagrass (Cynodon dactylon L. Pers. ✕ C. transvaalensis Burt‐Davy) grown on a Marvyn sl (typic Hapludult).

Results of the 3‐year study showed that N rates of 0.25 kg/are produce sod tensile strengths equal or superior to those obtained from rates as high as 1.0 kg/are. Applications of N made at 2‐week intervals produced sods with lower tensile strength than when applications were spaced 4 weeks apart. There were no significant interactions between N rates and application intervals. Both cultivars responded similarly; however, sod strengths for Tifway ranged from 30 to 50% greater than for Tifgreen in all tests. Varying mowing height from 1.25 to 2.50 an did not materially affect sod strength of either cultivar.
Soybean Yield Compensation with Different Populations and Missing Plant Patterns1
Authors: Stivers R. K. , Swearingin M. L.
Published: July 2010

Soybean [Glycine max (L) Merr.] populations are sometimes uneven because of skips or missing plants in a section of row. The relative amount of anticipated yield loss and compensation can be valuable in deciding to replant or not. This research compares soybean yields and yield components associated with skips of different lengths and arrangements using two cultivars in 76‐cm rows for two cropping years in northwest Indiana. Four‐row plots were used in two experiments having a randomized, complete‐block design with four replications. Skips in rows were made by removing plants before the V‐3 stage was reached. Skips were made in one interior row in the first experiment. Yields of the skip row declined as skips became longer. Several short skips reduced yields less than one long skip of the same total length. In an adjacent interior row with no skips, yields increased 0.4 to 18.3% over that of the check (3,712 kg/ha) adjacent to 0.76‐m and 3.05‐m skips, respectively. The ‘Woodworth’ cultivar yielded relatively more than ‘Wells’ in one year, particularly where longer (>0.30 m) skips occupied 50% of the total row length, mainly because Woodworth had more pods per plant. In the second experiment, where three of the treatments had different populations (10.5, 14.1, and 18.0 plants/m, yields remained the same (3,839 to 3,893 kg/ha). In the seven treatments with alternate skips in each row, yield reductions varied from 1.1% with 0.30.m skips to 15.3% with 1.22‐m skips in 50% of the entire row length. The constant yield in the three populations and relatively small decline in yield for the longer skips (0.61, 0.92, 1.22‐m) either in one‐fourth or one‐half of the total row length was due to compensation resulting from increases in numbers of branches per plant, increases in numbers of pods on branches and on the main stem, and increases in numbers of seeds per pod on branches as each plant was given more space. Increasing weight per seed played a small role.
Effect of Nitrogen and Phosphorus Fertilizers on a Bromegrass and Alfalfa Mixture Grown Under Two Systems of Pasture Management. I. Yield, Percentage Legume in Sward, and Soil Tests1
Authors: Nuttall W. F. , Cooke D. A. , Waddington J. , Robertson J. A.
Published: July 2010

Bromegrass (Bromus inermis L.) and alfalfa (Medicago media Pers.) herbage production in western Canada can be increased by the application of N and P fertilizers on soils deficient in these elements. This study was conducted to determine optimum pasture production, changes in botanical composition of the sward, and changes in nutrient concentration of Melfort silty clay soil (Typic cryoborolls) from the application of N‐P fertilizers on a 4‐year‐old stand of bromegrass and alfalfa under two pasture management systems. N fertilizer was applied at 0, 45, 90, 135, and 180 kg N/ha each year from 1970 to 1973 in combination with P fertilizer applied to one‐half of each plot at 0 and 20 kg P/ha from 1971 to 1973.

Total yield of bromegrass and alfalfa herbage expressed as a percentage of a control was significantly related to the application of N and P fertilizers and available soil P by regression analyses (R2 = 60.4%). Yields were as high as 251% of controls and ranged from 1,919 to 10,518 kg dry matter per ha. Higher herbage yields were obtained on pastures in which supplementary barlay (Hordeum vulgare L.) was fed to growing animals than on pastures with a “Put and Take” stocking system. The percentage of alfalfa in the sward was significantly reduced as much as 29.4% by N‐P fertilizers. A higher proportion of alfalfa in the sward was measured under the “Put and Take” treatment (36.9%) than the supplementary barley system (23.5%). Percentage alfalfa in the sward ranged from 13.8 to 54.8% (1972 to 1973, ranges C and A).

Nitrogen applied at 180 kg N/ha each year to pasture increased nitrate‐N in the soil profile to 31.5 µg N/g of soil at the 30 to 60‐cm depth. As a result of residual N and P fertilizer, increased herbage yields were obtained 3 years after fertilizer was applied. After this 3‐year period, nitrate‐N was low, 1.8 µg N/g soil or less, in the soil profile at all depths.

Nitrogen fertilizer at 90 kg N/ha and P at 20 kg P/ha produced an average increase in herbage yield of 74% or a total yield of 6,129 kg/ha. These rates gave the most economical return on fertilizer invested and did not increase nitrate‐N in the soil profile significantly.
Relationships Among Stalk Length, Leaf Area, and Dry Biomass of Sugarcane1
Authors: Shih S. F. , Gascho G. J.
Published: July 2010

Sugarcane (Saccharum spp.) is a leading contender in comparisons of biomass energy systems, however, scientific information on growth factors affecting biomass is limited and precludes establishing valid interrelationships for predicting biomass production. With that objective in mind, two sugarcane experiments were conducted at lysimeter and field sites to study the relationships among stalk length, leaf area index, and dry biomass. Three replications of five cultivars ‘CP 63‐588,’ ‘CP 56‐59,’ ‘CP 65‐357,’ ‘C1 54‐378,’ and ‘C1 54‐336’ were planted in six lysimeters where water tables were maintained at 30, 60, and 90 cm. Cultivar ‘CP 65‐357’ was planted in the field at 0.5 and 1.5 m row spacings. Leaf area and the stalk length were measured. Two equations involving leaf area were developed. The first equation estimated leaf area (Y) from stalk length (X) by an exponential‐hyperbolic function; i.e. Y = Exp [X/(1.140 + 0.111X + 0.177 ✕ 10−4 X2)]. The second equation predicted dry biomass (DB) from the cumulative time interaction with leaf area index (CTXLAI), i.e. DB = Exp [CTXLAI/(0.388 + 0.280 CTXLAI)]. The relationships developed should be useful for easily estimating sugarcane biomass.
In Situ Study of Corn Seedling Root and Shoot Growth by Neutron Radiography1
Authors: Couchat Ph. , Moutonnet P. , Houelle M. , Picard D.
Published: July 2010

In corn (Zea mays L.) root and shoot studies particular attention has been paid to environmental and soil influence on seedling root growth. Experimentation in this field has been limited by the difficulty in investigating root elongation, since no nondestructive in situ method was available other than glass‐sided boxes. The purpose of this study was to show that the neutron radiography is capable of supplying in situ root images permitting qualitative and quantitative interpretation so that comparative root and shoot growth may now be analyzed in a new way.

The experiments consisted of shoot and root growth studies up to 21 days for two corn seeds sown at depths of 1 and 6 cm. The plants were grown in a growth chamber in a 2‐cm‐thick aluminum box containing coarse sand maintained at 8% volumetric water content. Daily neutron radiographs were made by the direct method using the 3.2° diverging thermal neutron beam of the MIRENE reactor at Valduc, France.

The images obtained allowed a qualitative interpretation not only for seminal root but also for laterals. Root development was not harmed visibly by irradiation and repeated environmental changes due to neutron radiography experiments. The seminal root elongation rate was analysed vs. the plant age. Quantitative data show that the root growth was greater during the day than at night. Root and shoot lengths were related in a linear manner between 7 and 15 days after sowing.
Residual Effects of Labeled N in Field Trials1
Authors: Broadbent F. E.
Published: July 2010

Field trials utilizing 15N‐depleted fertilizer were conducted over a 6‐year period at two locations for the purpose of providing as complete an accounting as possible of N in the soil‐plant‐water system under conditions of irrigated agriculture. These trials permitted measurement of residual effects while continuing a constant rate of N application, and also after applications were discontinued. On Yolo fine sandy loam (Typic xerorthent) residual value of the previous year's fertilizer varied from negligible to 23% of the total crop uptake depending on N rate and amount of irrigation water applied. These values were equivalent to 5 to 91 kg N/ha of a current year's N application. In Hanford sandy loam (Typic xerorthent) 51 to 60% of the N in a corn (Zea mays L.) crop was labeled N in the year following discontinuance of N application and about 32% in the second year. Most of the residual N subsequently utilized by a crop was in the inorganic form. There was little evidence of remineralization of labeled organic N.

At fertilizer rates that were adequate, but not excessive, for maximum grain yield coupled with adequate irrigation water the residual N was equivalent to 3 to 24 kg/ha. It is concluded that with efficient management which avoids overfertilization, the value of residual N is not sufficient to affect application rates. Substantial quantities of residual N reflected overfertilization and/or insufficient irrigation water in previous years.
Physiological Aspects of Yield Improvement in Soybeans1
Authors: Gay Scott , Egli D. B. , Reicosky D. A.
Published: July 2010

An understanding of the physiological changes that have occurred in cultivar development in the past would be helpful in the continued production of high yielding cultivars of the various crop species. Field experiments using conventional cultural practices with supplemental irrigation were conducted in 1976 to determine the physiological basis for yield differences between old, low yielding soybean [Glycine max (L.) Merr.] cultivars (Lincoln' and ‘Dorman’) and new high yielding cultivars (‘Williams’ and ‘Essex’). Mechanical support was used to prevent lodging for comparison to control plots with no mechanical support. There was no lodging in Lincoln and Williams (Maturity Group III); whereas, in maturity group V, Dorman lodged significantly more than Essex in the control plots. However, there was no relationship between lodging and yield. Williams produced 34% more yield than Lincoln, primarily because of larger seed. Essex produced 88% more yield than Dorman, primarily because of more seed per unit area.

Yield differences were not correlated with total shoot weights or CO2 uptake rates of a single leaf during vegetative or early reproductive growth. Rates of acetylene reduction were similar for Williams and Lincoln, but Essex had a higher rate than Dorman. The yield advantage of Williams resulted partially from a longer filling period (12%), which was associated with higher CO2 uptake and acetylene reduction rates late in the filling period. Essex and Dorman produced similar total shoot weights late in the filling period, so the yield advantage for Essex resulted from partitioning more photosynthate to the seed. The data suggest that yield improvement in the future may be possible by lengthening the filling period. It may not be possible to increase seed yields by increasing the partitioning of photosynthate to the seed if the partitioning in current cultivars is approaching the maximum.
Tests to determine Wheat Straw Decomposition1
Authors: Armbrust D. V.
Published: July 2010

Crop residues are important for erosion control and maintaining soil fertility, but these residues could also be used for other pnrposes. To determine the amount of excess residues available for other uses, we need a simple, accurate method to measure residue decomposition. Three methods were evaluated to determine residue losses by decomposition. Wheat (Triticum aestivum L.) straw was enclosed in nylon envelopes, buried 6 cm deep in a loam soil in greenhouse benches, and recovered periodically during 9 months. Assays for acriflavine (acriflavine hydrochloride) adsorption on 0.1 N NaOH‐extractable humic materials, light absorption of the extracted humic materials, and the force necessary to break the straw were compared with weight loss by decomposition

Light absorption and break force were linearly related to residue loss with regression coefficients of − 0.95 and − 0.92, respectively. Break force approached zero after 2 months. Acriflavine adsorption was poorly related to straw loss. The light‐absorption technique may be used to measure decomposition of crop residues freely mixed Within the soil once the relationships between percent transmittance and loss by decomposition are established.
Forage Quality Response of Tall Fescue, Orchardgrass, and Phalaris to Soil Fertility Level1
Authors: Odom J. W. , Haaland R. L. , Hoveland C. S. , Anthony W. B.
Published: July 2010

Poor steer performance was obtained on a tall fescue (Festuca arundinacea Schreb.) pasture on an acid soil while a nearby tall fescue pasture on a calcareous soil gave excellent steer performance. A greenhouse experiment using five soils was designed to test the effects of soil Ca and Mg levels on the digestibility and mineral composition of three cool season, perennial grasses. Soil Ca and Mg levels were associated with Ca and Mg concentrations in the herbage of tall fescue, orchardgrass (Dactylis glomerata L.) and phalaris (Phalaris aquatica L.) but concentration of Ca in the herbage had no effect on in vitro dry matter digestibility. Tall fescue had higher concentrations of Ca and Mg and lower concentrations of K than the other grass species grown on each of five soil.
Drought Adaptation of Cowpea. II. Influence of Drought on Plant Water Status and Relations with Seed Yield1
Authors: Turk Kenneth J. , Hall Anthony E.
Published: July 2010

Concurrent studies described the drought resistance of cowpeas [Vigna unguiculata (L.) Walp.] during the vegetative stage, and susceptibility to drought during flowering and pod filling. The present field studies were conducted to examine possible mechanisms of cowpea adaptation to drought and relations between yield and plant water status to guide programs for the development of improved cultivars and irrigation practices.

Two cowpea cultivars were subjected to different levels of irrigation at the vegetative, flowering, and pod filling stages using a line‐source sprinkler system during 2 years having contrasting weather patterns. The soil is an Arlington fine sandy loam (coarse‐loamy, mixed, thermic Haplic Durixeralf) with a high bulk density. Soil water content was determined with a neutron scattering device and plant water status measurements were made with a pressure chamber and thermocouple psychrometers. The plants exhibited extreme drought avoidance in the presence of soil water deficits or high evaporative demands with xylem pressure potential remaining above −18 bar. Drought avoidance by cowpeas appeared to be mainly due to several mechanisms for regulating water loss. Predawn xylem pressure potential was more consistently related to soil water deficits than afternoon values. Leaf solute potential was correlated with xylem pressure potential, becoming more negative in the afternoon than predawn. Solute potential also was more negative during periods of high evaporative demands but was only slightly reduced by soil water deficits.

Seed yield was linearly correlated with seasonal cumulative xylem pressure potential measured either just before sunrise or in the afternoon. Consequently, the pressure chamber may provide guidelines for research on irrigation management and the selection of cultivars with improved drought tolerance. However, because of the large differences in seed yield associated with small differences in cumulative xylem pressure potential the pressure chamber may not be useful as an indicator for commercial irrigation of cowpeas.
Emergence Force by Cotton Seedlings1
Authors: Gerard C. J.
Published: July 2010

Economic returns from crops require establishment of a good plant stand. Soil crusting reduces seedling emergence and stands of many crops throughout the world. One of the most important crops adversely affected by crusting is cotton (Gossypium hirsutum L.). The force exerted by germinating plants such as cotton often determines the seedling's ability to rupture and emerge from under the soil crust. However, the force exerted by an emerging cotton seedling has not been determined. Studies were conducted in the laboratory to determine and better understand the emergence force of cotton seedlings.

The force exerted by cotton seedlings under different soil moisture conditions and temperatures was determined using a force transducer. The transducer mv output, which is a linear function of the force exerted against the transducer button, was continuously monitored with a mv recorder.

Emergence force was a linear function of volumetric soil moisture, number of seedlings, and cross‐sectional area of the emerging hypocotyls. The size of the hypocotyl was a function of soil moisture and temperature. Maximum diameters of the cotton hypocotyl at 22, 27, 32, and 40 C were 0.32, 0.41, 0.34, and 0.26 cm, respectively, and the maximum forces exerted were about 350, 600, 400, and 200 g, respectively. The time required for maximum exertion by the seedling was dependent upon temperature, ranging from 40 to 48 hours at 32 C and 50 to 60 hours at 27 C. These findings suggest that planting methods, planting dates, and cultivar improvement may offer possible ways to minimize or circumvent crusting effects and increase emergence.
Effects of Diurnal Variation in Light and Temperature on the Acetylene Reduction Activity (Nitrogen Fixation) of Subterranean Clover1
Authors: Eckart Jeffrey F. , Raguse Charles A.
Published: July 2010

Singly, or in combination, both light intensity or temperature can limit symbiotic N fixation. Most reported studies have been done to investigate the effects of only one of these factors. The present study was done to determine N fixation response to variation in both light and temperature for an annual range legume which, during its normal growing season, may be subject to growth limiting levels of both environmental factors. Plants of subterranean clover (Trifolium subterraneum L., ‘Mt. Barker’) were grown from seed to the sixth trifoliolate leaf stage in sand with N‐deficient nutrient solution. Plant containers were designed to permit sampling of the rooting atmosphere for acetylene reduction assay during treatment conditions, which were maintained with controlled‐environment facilities. During the treatment phase light and temperature were investigated by: 1) varying both diurnally; 2) varying light diurnally under constant temperature; 3) varying temperature diurnally under constant light; and 4) maintaining both light and temperature constant. Apparent N2 fixation (acetylene reduction) showed diurnal fluctuations under: 1) constant light; and 2) 12/12 hour light/dark regimes when root and air temperature fluctuated by 7 and 14 C, respectively. In constant temperature and either normal photoperiods or constant light, however, no significant diurnal fluctuation of acetylene reduction was measured. Under both constant temperature regimes a gradual increase in acetylene reduction activity, which may have been an artifact, was observed. These results show that diurnal changes in acetylene reduction by subterranean clover result more from fluctuations in temperature than from diurnal changes in light and suggest that N2 fixation by root nodules of this species is buffered against short‐term changes in photosynthate supply.
Effect of the Hydrogenase System in Rhizobium japonicum on the Nitrogen Fixation and Growth of Soybeans at Different Stages of Development1
Authors: Zablotowicz R. M. , Russell S. A. , Evans H. J.
Published: July 2010

The process of N fixation is energy consuming and inefficient. In most cases 20 to 40% of the energy that is supplied to nitrogenase for the reduction of N2 is utilized for the reduction of protons to H2. Some strains of R. japonicum contain a membrane‐bound hydrogenase that is capable of oxidizing all of the H2 that is produced during N2 fixation. This study was conducted to evaluate the effects of inoculation of soybeans [Glycine max (L.) Merr.] with Rhizobium japonicum containing H2 recycling capability on N fixation efficiency and soybean yield at various physiological stages of growth.

In these experiments, a H2‐oxidizing strain SR (Hup+) and SR3 (Hup−), a mutant derived from SR which is unable to oxidize H2, were utilized. Soybeans cv. ‘Wilkin’ were grown under bacteriological conditions utilizing a drip‐irrigated nutriculture system. Nodules from plants inoculated with SR evolved no measurable amount of H2, while nodules from plants innoculated with SR3 evolved between 2.7 and 10 µmoles of H2/g nodules/ hour depending upon physiological age. Acetylene reduction rates by strain SR were significantly higher than those of nodules formed from SR3 during the vegetative, late pod‐fill, and leaf senescence stage of growth, respectively. Dry matter accumulation was significantly higher in plants inoculated with SR than in plants inoculated with SR3 (31% increase during vegetative stage, 25% during flowering, and 27% during pod‐fill stage). Nitrogen contents of shoots and seeds were significantly higher in plants inoculated with strain SR, demonstrating increased N fixation by nodules formed by Hup+Rhizobium. Our results support the conclusion that strains of R. japonicum selected for inoculation purposes should contain H2‐oxidizing capability as one of their desired characteristics.