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doi: 10.2134/agronj1973.00021962006500050002xpmid: N/A
Orchardgrass (Dactylis glomerata L.) pastures and the N fertilization of these pastures are important to beef cattle production in the humid and subhumid parts of the United States. Nitrogen in excess of 200 kg/ha per year is required for economic yields. We studied the influence of two levels of N (270 and 540 kg/ha per year) on forage yield, concentration of NO3‐N, N, P, and K or 23 orchardgrass varieties from diverse areas of the world.
Geronimo, J.; Smith, L. L.; Stockdale, G. D.; Goring, C. A. I.
doi: 10.2134/agronj1973.00021962006500050003xpmid: N/A
Previous laboratory studies have shown that nitrapyrin (2‐chloro‐6‐(trichloromethyl) pyridine) can produce phytotoxicity in certain plants. Nitrapyrin hydrolyzes in soil to 6‐chloropicolinic acid; however, the phytotoxic properties of the latter compound have not been compared with those of the former. Therefore, studies were conducted to compare the relative toxicity of nitrapyrin and 6‐chloropicolinic acid to the seedlings of various crop plants, to compare their phytotoxicity in a variety of soils, and to estimate if the soil concentration, of either chemical, required to produce significant growth reduction is less than recommended field application rates for nitrapyrin. Nitrapyrin was more toxic than 6‐chloropicolinic acid to the graminaceous species tested which included corn (Zea mays L.), sorghum (Sorghum vulgate L.), wheat (Triticum aestivum L.), and rice (Oryza sativa L.). 6‐Chloropicolinic acid was more toxic than nitrapyrin to the dicotyledenous species tested which included cotton (Gossypium hirsutum L.), sugar beet (Beta vulgaris L.), tomato (Lycopersicon esculentum L.), alfalfa (Medicago sativa L.), and soybean (Glycine max L.). The dicotyledenous species were more sensitive to both compounds than were the graminaceous species. All species tested except alfalfa and tomato tolerated soil concentrations of nitrapyrin estimated to be greater than the highest recommended field application rates. Nitrapyrin was more highly adsorbed and therefore detoxified to a greater extent than 6‐chloropicolinic acid when soil organic matter increased.
Geronimo, J.; Smith, L. L.; Stockdale, G. D.
doi: 10.2134/agronj1973.00021962006500050004xpmid: N/A
Nitrapyrin (2‐Chloro‐6‐(trichloromethyl) pyridine) is a selective nitrification inhibitor and 6‐chloropicolinic acid is its principal metabolite in plants and soil. Nitrapyrin has been found to produce more phytotoxicity on some graminaceous species than 6‐chloropicolinic acid, and the opposite has been found for some dicotyledenous species. This study was conducted to determine if the differences in activity observed with nitrapyrin and 6‐chloropicolinic acid on some monocotyledenous and dicotyledenous species could be due, at least in part, to differences in the site of exposure of the seedlings to the two chemicals. Chemically treated bands of soil were placed either above or below the seeds of cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.), and the effect of the chemicals was assessed by weighing top growth of the plants. Nitrapyrin reduced the top growth of both cotton and wheat when exposure occurred through both the roots and shoots of the germinating seedlings. 6‐Chloropicolinic acid reduced the top growth of both species when exposure occurred through the roots only. The site of exposure of the germinating seedlings to the chemicals influences the degree of phytotoxicity obtained. The inherent activity of each compound against each species, however, appears to be a more important factor with regard to phytotoxicity.
doi: 10.2134/agronj1973.00021962006500050005xpmid: N/A
The method and rate of nitrogen fertilization of muskmelons (Cucumis melo) on sandy soils is of concern because of the leaching potential of N. The relative availability of nitrogen from ammonium nitrate, urea‐formaldehyde, and sulfur coated urea (SCU) was studied in the field with regard to influence on growth, leaf and petiole composition, and fruit yield of muskmelon. The field studies compared various nitrogen materials in different timing and rate schedules. The fertilizers were used at 0, 33, 66, 99, 132, and 264 kg/ha in single (preplant) and split (preplant + sidedressing) applications. Data were collected for 4 seasons. In each year N application increased vine growth and intensity of the green color of the leaves. The N concentration of the recently mature melon leaves was increased more by NH4NO3 than by urea‐formaldehyde or SCU. The relationship of N rate was linear with N composition but parabolic with yield. Optimum plant growth and fruit yields were obtained with a preplant application of 80 to 90 kg/ha. The same total N rate as a split application or as a less available N source was not as effective for fruit yield production. The increased yield from N treatment was due to increased vine size and increased numbers of fruit. Optimum fruit yields were produced at leaf composition of total N over 4.5% or petiole content of NO3‐N over 15,000 ppm during vegetative and fruit initiation stages. Sulfur coated urea with 37% dissolution rate produced NO3‐N and total N concentrations of petioles about equal to the same N rate as NH4NO3; SCU with 12% dissolution rate resulted in NO3 concentrations equal to one‐quarter the N rate as NH4NO3 at the runner stage and equal to one‐half the N rate as NH4NO3 just prior to harvest.
Anderson, F. N.; Peterson, G. A.
doi: 10.2134/agronj1973.00021962006500050006xpmid: N/A
Continuous corn (Zea mays L.) was produced from 1912 to 1972 on an irrigated soil of the Typic Haplustoll group in western Nebraska. Corn yields declined rapidly from 1912 to 1922 when no manure or N fertilizer was used. Annual applications of manure on one‐half of the plot area beginning in 1941 increased yields linearly until 1953. Nitrogen fertilization beginning in 1953 increased corn yields 4685 kg/ha above the control during the first year of application on the nonmanured treatment. Maximum yields have been reached with a combination of manure and N fertilization. Total soil N data indicate that manuring from 1941 to 1972 has returned the soil N level to about 90% of the level that was present in the uncultivated soil in 1912.
doi: 10.2134/agronj1973.00021962006500050007xpmid: N/A
To evaluate the comparative costs of controlled‐environment and field research, a ledger has been formulated to consider the base expenditures—those expenses incurred in the routine operation of the field and controlled‐environment facilities—and the variable expenditures—those incurred in the acquisition of samples and the various chemical, physical, and morphological analyses dictated by the needs of a particular investigation. For a comparable experiment, the base cost of growth‐chamber space in the North Carolina State University Phytotron is more than fivefold the base cost for field‐acreage. This relatively high base cost for controlled‐environment research is offset by a greater variable cost encountered with field research.
doi: 10.2134/agronj1973.00021962006500050008xpmid: N/A
Optimum rates for and the residual effects of several new copper fertilizer materials have not been determined. Because the copper in these sources is complexed, usually with an organic ligand, it has been implied that they are more effective than copper sulfate.
doi: 10.2134/agronj1973.00021962006500050009xpmid: N/A
An understanding of the seasonal dry matter accumulation pattern of the sorghum [Sorghum bicolor (L.) Moench] plant under varying fertility levels is important for planning an efficient fertilization program. Field experiments were conducted to determine the effects of varying rates of N (0, 60, and 120 kg/ha) on the dry matter accumulation pattern, yield, and grain N content of a sorghum hybrid. Plant samples were collected at weekly intervals and partitioned into component parts for dry matter estimation.
doi: 10.2134/agronj1973.00021962006500050010xpmid: N/A
Crop response to N can be difficult to predict under semitropical irrigated conditions. To aid in the explanation of erratice N response, studies were conducted over a 4‐year period to determine the influence of cotton (Gossipium hirsutum L.) and sorghum (Sorghum bicolor (L.) Moench.) on NO3‐N distribution in a clay soil profile and its effect on subsequent crop response to applied N. Double‐cropping systems used in the study were cotton— winter vegetable and sorghum—winter vegetable with plots split to include N rates of 0, 67, and 134 kg/ha. Nitrate nitrogen determinations were made periodically from soil samples taken from profiles of each treatment. Where sorghum was grown for 3 years, the profile was depleted of NO3‐N to a depth of 120 cm. In contrast, where cotton was grown NO3‐N accumulated at the 60 to 120 cm depth. This resulted in little response to residual N by mustard (Brassica juncea) after sorghum, but residual N from applications of 134 kg/ha per year to cotton precluded a response to N applied to winter mustard. These studies indicate that the depleted soil profile after sorghum results in a need for higher rates of N fertilizer on crops following sorghum than those following cotton.
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