Forage yields of five grass species: Agropyron cristatum (L.) Gaertn., A. smithii Rydb., Lolium perenne L., Poa pratensis L., and Puccinellia distans (L.) Parl., were studied in soil under greenhouse conditions with NaCl additions of 0; 5,000; 10,000; and 20,000 ppm. Forage yield of P. distans was reduced 23% by addition of 20,000 ppm NaCl, compared to a minimum reduction of 40% for the other grass species. Addition of 30,000 ppm NaCl to soil completely inhibited seedling survival of A. cristatum, A. smithii, Elymus triticoides Buckl., P. distans, Puccinellia lemmoni (Vasey) Scribn., and Sporobolus airoides (Torr.) Torr. Puccinellia airoides (Nutt.) Wats. and Coult. and P. distans were unusually toleran to foliar applications of NaCl in the field.Mineral analysis of leaf tissue by emission spectroscopy showed that Na concentrations increased as NaCl addition to the soil increased. However, there was no relationship between salt tolerance of the various grasses and amounts of Na in leaf tissue. Increased NaCl addition to the soil resulted in decreased leaf Ca and Mg, but no relationship existed between leaf K and NaCl addition.P. distans is of value for vegetating saline roadsides.
Field experiments were conducted to study the effects of 2‐chloro‐6‐(trichloromethyl) pyridine, N‐Serve, on nitrification of anhydrous NH3. Applications of 0, 0.56, and 1.12 kg N‐Serve/ha in all possible combinations with 0, 112, and 224 kg N/ha were made on March 30, June 4, and November 25, 1968. Concentrations of NH4+‐N in the NH3 retention zones were determined at various times following application. N‐Serve decreased the rate of nitrification. Nitrification inhibition was evident at the first sampling (14 to 41 days from NH3 application) and persisted until almost all NH4+ had nitrified. N‐Serve was inhibitory at all locations within the NH3 retention zone. As an average of all application dates and N rates, there was 52% as much NH4+ present at the first sampling with no N‐Serve as with 1.12 kg/ha of N‐Serve. There was 82% as much NH4+ present at the first sampling with 0.56 kg/ha N‐Serve as with 1.12 kg/ha N‐Serve.
A method for marking the point of anhydrous ammonia release is described. A steel tube welded to the back of the ammonia applicator knife serves to place a twine marker at the point of release as ammonia is injected into the soil. The twine can then be readily located several months later if sampling of the ammonia application zone is desired.
The frequency and extent of fungicide use on putting green turfgrasses prompted investigations to determine the effect of three commonly used fungicides on N transformations in soil. Laboratory and field studies were conducted to study the effect of the following fungicides on nitrification and N mineralization in soil: benomyl [(methyl l‐(butylcarbamoyl)‐2‐benzimidazolecarbamate)], rene [(2,4‐dichloro‐6‐(0‐chloranilino)‐s‐triazine)], and rnaM‐7 neb (manganese ethylenebisdithiocarbamate). In laboratory studies, the three fungicides were added at rates of 0, 25, 75, and 150 ppm and the soil incubated at 21±1 C and moisture content of 30±1%. Analyses for NH+4‐N and (NO‐2 + NO‐3)‐N were conducted at various times during a 16‐week incubation period. Almost no effect was detected for benomyl, but a complete blockage occurred at the 150 ppm rate of maneb. Dyrene had an intermediate effect. Based on concentrations of (NH+,4 + NO‐2 + NO‐3)‐N in the untreated control as compared to treated soil, benomyl was stimulatory to N mineralization. Inhibitory effects were observed for both Dyrene and maneb after 4 weeks of incubation, but these effects had disappeared after 16 weeks. In the field, 14 weekly applications of benomyl, Dyrene, and maneb at 90, 90, and 135 g active ingredient/are were made to a ‘Penncross’ creeping bentgrass, Agrostis palustris Huds., golf green. Soil samples were taken from a depth of 0 to 2.5 cm (excluding thatch) and determinations of NH+4‐N and (NO‐2 + NO3‐)‐N concentrations were made at weekly intervals during a 5‐week incubation. There was no effect of any of the fungicides on nitrification but enhanced N mineralization occurred with application of all three of the fungicides. The differences in the effects of these fungicides on nitrification and N mineralization in laboratory as compared to field applications were considered to be the result of lower rates of application associated with more rapid rates of degradation under field conditions as contrasted with the high single rates of application under laboratory conditions.
The effect of 0, 2, 4, 8, 16, and 32 ppm KN3 on nitrification in soil was studied at 30 and 10 C. At both temperatures, KN3 was an effective nitrification inhibitor. At 30 C, 75 ppm of added NH4 + disappeared in 2 weeks where no KN3 had been added as compared to 4 weeks at the 32 ppm KN3 rate. At 10 C, 4 weeks were required for the NH4+ to disappear at 0 ppm KN3, whereas more NH4+ was present after 18 weeks than initially where 32 ppm KN3 was applied. Concentrations of (NO2‐ + NO3‐)‐ N were found to be similar at all KN3 rates once the NH4+ had disappeared. This indicates that KN3 had no effect on mineralization‐immobilization relationships. The soil pH for both incubation temperatures was 6.8. The effect of 4 ppm KN3 in soil incubated at 30 C was studied at soil pH levels of 4.5, 6.0, and 7.5. The NH4‐N and (NO2‐ + NO3‐)‐N concentrations during 4 weeks incubation indicated that KN3 did not inhibit nitrification at soil pH levels of 4.5 and 6.0 but that nitrification was inhibited at pH 7.5. At 30 C, KN3 does not appear to be an effective nitrification inhibitor for soils of pH less than 6.0.
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