摘要:

Water containing 3.6, 7.2, or 10.8 mmol N/L and uniformly supplied with 2.0 and 5.0 mmol/L of P and K, respectively, was used for irrigating greenhouse‐grown French beans (Phaseolus vulqariscv. ‘Blue Lake'). The fertilizers were applied with every irrigation via the irrigation stream. The plants were grown in pots, each filled with 12 kg of soil. In all treatments a 0.3 leaching fraction was allowed. The total amounts of N applied in a total amount of 180 L water per pot were 9, 18, and 27 g/pot for the three N levels, respectively.

ISSN:0010-3624    

DOI:10.1080/00103628609367761

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Heavy applications of ammonium‐based N fertilizers on cereal crops have resulted in rapid acidification of once neutral soils in northern Idaho. Lime and elemental S applications were used to manipulate soil pH and evaluate consequent effects on the growth of lentils (Lens culinarius) and winter wheat (Triticum aestivumL.). Lime applications of 2,200 and 4,400 kg/ha resulted in 22 to 23% and 10 to 28% yield increases of lentils and winter wheat, respectively. Elemental S application rates of 2,200 and 4,400 kg/ha reduced: (1) soil pH in the surface 30 cm of the soil profile, (2) lentil and winter wheat yields, (3) populations ofRhizobium leguminosarumin the soil, and (4) N mineralization rates. Soil pH should be maintained at or above 5.6 for lentils and 5.2 for winter wheat production.

ISSN:0010-3624    

DOI:10.1080/00103628609367762

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Nitrogen use efficiency and response of sunflower (Helianthus annuusL.) to timing and rate of surface banded N was characterized in a split‐plot 4x2 factorial experiment. Nitrogen rates (main plots) were 0, 34, 67, and 134 kg ha‐1at Mississippi State and 0, 45, 90 and 180 kg ha‐1at Brooksville, MS. Nitrogen, applied as NH4NO3, was surface banded either at planting or at the four leaf stage (subplot). Seed yield was significantly influenced by rate of N application at both locations. Seed yield showed a quadratic response at Mississippi State and a Mitscherlich‐type response at Brooksville. Maximum seed yields of 2606 and 2380 kg ha‐1were obtained at the respective sites. Sunflower responded to N fertilizer application when inorganic N content of the soil to 60 cm depth at planting was less than 50 kg ha‐1. Nitrogen efficiency was influenced by rate and timing of application, exhibiting exponential declines with increasing N rates. Fertilizer losses at the highest rates of applied N were 19 and 52% at Mississippi State and Brooksville, respectively. Clay‐fixed NH^+accounted for 26% of the applied N fertilizer loss at Brooksville. Nitrogen fertilizer efficiency and recommendations for sunflower could be improved if initial soil inorganic N is taken into account.

ISSN:0010-3624    

DOI:10.1080/00103628609367763

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

An inexpensive hand held reflectometer was used to estimate NO3concentration with Merckoquant NO3indicator strips. For KNO3solutions a fourfold improvement in precision was obtained over the visual method of colour comparison. The instrument calibration was stable over several days and not affected by temperature in the range 8–34oC. The reflectometer showed quantitatively that increasing temperature (8–34oC) reduced the optimal time for reading the strips from 120s to 40s. With standard NO3solutions a simple hyperbolic transformation of the reflectometer readings produced a linear calibration of good fit (r2=0.99). NO3could be estimated in different soil types within half an hour. The results agreed well with values from ion chromatography (r2=0.97, slope=1.07). Plant sap analysis was moderately precise (r2=0.92) but inaccurate and underestimated by more than 60% values obtained by ion chromatography. This discrepancy was not caused by the reflectometer but seemed to be due to factors within the plant sap that interfered with the NO3colour reaction in the Merckoquant strips.

ISSN:0010-3624    

DOI:10.1080/00103628609367764

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

One approach to evaluating computer models which predict terrestrial‐aquatic ecosystem response to acid deposition is the experimental acidification of soils with subsequent comparisons among predicted and measured soil solution response. Using a soil microcosm experimental approach, comparisions between simulated acid rain (i.e. dilute H2SO4), dry NH4NO3, and prilled reduced S were made for suitability for large‐scale field experiments. Soil microcosms consisting of reconstructed soil profiles received a background simulated throughfall dosing over the six month treatment period. Results indicated that simulated throughfall, applied at twice the ambient rate, acidified soil leachates approximately 0.5 pH units over the treatment period. Along with the decline in leachate pH was an apparent release of base cations as well as Fe and Al. Over the length of the treatment period, very little of the prilled S dissolved and the simulated acid rain treatment did not have significant effects on leachate chemistry.

ISSN:0010-3624    

DOI:10.1080/00103628609367765

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Coker 7473wheat (Triticum aestivumL.) was grown on Keo silt loam (coarse‐silty, mixed, thermic Dystric Fluventic Entrochrepts) with four S sources applied at various rates for two years. The innate S level of this soil was not adequate for optimum grain yield; therefore, additional S significantly increased grain yield and S concentration and decreased N/S ratios in wheat tissue. Minimum S concentration and N/S ratios in plant tissue for maximum yield ranged from 1.3 to 2.73 g S/kg and 9.5 to 19.2, respectively.

ISSN:0010-3624    

DOI:10.1080/00103628609367766

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A procedure is proposed for measuring nitrogen mineralization and nitrification in intact soil cores. The method relies on ion exchange resins to trap ammonium and nitrate entering and leaving cores of soil otherwise open at the top and bottom. Changes in soil concentrations plus an accounting of ions trapped by the lower resin after field incubations, indicate rates of nitrogen reactions. Using this technique, we estimated net ammonification rates from 0–36 mg N/kg/mo and nitrification rates from 0–16 mg N/kg/mo for the surface of a sandy, low nutrient soil under pine cultivation in north Florida; higher rates occurred after urea fertilization. The procedure has potential advantages over others, but must be more fully evaluated under a variety of conditions.

ISSN:0010-3624    

DOI:10.1080/00103628609367767

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Cation exchange capacity (CEC) of the 0–5 cm depth of forest soils increased with the square root of solution ionic strength over the experimental range of 6 to 96 mM. Percentage increases in CEC were positively correlated with percentage organic carbon; for mixed hardwood forest soils, increases were38%for soils with 3.3% carbon, and 105% for soils with 7.4% carbon when ionic strength was varied over the full experimental range. When analyzing soils with constant‐potential surfaces, both pH and ionic strength must be controlled, preferably at or near levels found in the field, in order to provide interpretable measures of CEC.

ISSN:0010-3624    

DOI:10.1080/00103628609367768

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Winged bean (Psophocarpus tetragonolobus) (L.) DC) seedlings of the accession TPT‐1, were grown in a greenhouse with graded, balanced total soluble salt (TSS) concentrations. After 4.5 days, plant height increased quadratically, with a maximum (149 cm) at 3000 ppm TSS. Seedlings were shortest at 1000 and 10,000 ppm TSS, 44.0 and 79.0 cm, respectively. Fresh weight of shoots increased quadratically with greatest weight, 29.03 g, at 5000 ppm TSS. Percent dry matter increased linearly with increasing TSS. Concentration of N, K and P increased quadratically with an increase in the TSS concentration in the growth medium. Concentration of Ca decreased quadratically with increasing TSS. Among the micronutrients, Fe and Mo concentration was quadratic, both elements were highest in the seedlings at 1000 and 10,000 ppm TSS rates. Concentrations of Mn and Zn increased linearly with increasing TSS. Winged bean seedlings at the 1000 to 3000 ppm TSS rates had spindly stems and a sparse, yellow foliage, typical for winged bean seedlings observed in the field during the first 4 to 5 weeks of growth. Seedlings at the 4000 and 5000 ppm TSS rates had sturdy stems and an abundant green foliage. At higher TSS concentrations, 5000 to 10,000 ppm TSS, seedlings had short intermodes and dark green foliage.

ISSN:0010-3624    

DOI:10.1080/00103628609367769

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628609367760

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor