摘要:

This paper reviews the literature on acid rain, with emphasis on soils and leaching of soil elements. Several questions still exist concerning the effects of atmospheric acid deposition on soils: 1) does acid rain enhance mobilization of harmful heavy metals in soils which could leach into the groundwater; 2) does acid rain accelerate the kinetics of weathering of primary minerals and of secondary clay minerals in soils which would release large quantities of Al, Fe, and Si into the groundwater making it unfit for human consumption; and 3) do the beneficial effects of acid deposition outweigh the negative effects or vice versa? Literature pertaining to these questions is addressed in this review.

ISSN:0010-3624    

DOI:10.1080/00103628509367636

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effects of foliar fertilization on the yield and seed composition of two soybean (Glycine maxL. Merrill) varieties were investigated under mid‐Missouri conditions over a 2‐year period. The foliar fertilizer treatments consisted of (i) 80–8–24–4 (NPKS) kg/ha, (ii) 40–4–12–2 (NPKS) kg/ha, and (in) control (no foliar treatment) with the optimum proportion of N:P:K:S in the solution 10:1:3:0.5 respectively. Nutrient sources were urea, potassium polyphosphate, and potassium sulfate. Water solutions of fertilizers (pH 6.9) containing 0.1% Tween 80 (v/v) were sprayed on the plants using a CO2‐ pressurized back‐pack sprayer. Foliar fertilizer was split between four equal applications during the seed filling period. The variety Mitchell at the higher rate and the variety Williams at the lower fertilizer application rate produced slight, though statistically insignificant, yield increases. At the higher rate of application, the seed protein contents of both varieties increased, while the oil contents decreased. The concentrations of P and K in the seeds were not affected by foliar fertilization, but at the higher rate, there was a small decrease in S content of Williams variety.

ISSN:0010-3624    

DOI:10.1080/00103628509367637

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

In spite of a high N requirement, sweet sorghum hasn't shown a consistent response to N fertilization. This research was designed to study the effect of N fertilization on sweet sorghum as affected by rates and time of N application. Five experiments were conducted under field conditions, where 0, 50, 100 and 150 kg N/ha were applied at sowing, and 35, 40, 55, 60 and 80 days after plant emergence. The soil had textures varying from sandy loam to clay, and organic matter contents from 0.67% to1.9%.The highest yields were observed when N was applied early in the season, showing that for sweet sorghum, sidedressing with N is not necessary. All the N can be applied at planting time, which allows the highest fertilizer use efficiency. On the other hand, late applications of N fertilizer (after 40 days), when the floral primordia is already visible, has little effect on stalk or grain yield. In this situation, a double or triple rate had to be applied to overcome the low efficiency of N utilization. There was no great advantage in splitting the sidedressed N rate. On the other hand, it was impossible to link the response to N to soil analysis as performed in most of Brazilian laboratories.

ISSN:0010-3624    

DOI:10.1080/00103628509367638

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Soybean (Glycine max(L.) Merrill) has been shown to have a great capacity to take K from soil, suggesting that it might absorb K from non‐exchangeable forms. In this paper, the effect of level of K fertilization on soil exchangeable K content and K uptake by soybean are discussed. The experiment was conducted on a Typic Haplortox (sandy loam), fertilized with 0, 40, 80, 160 and 240 kg K2O/ha as KC1 or K2SO4. During five years before the experiment, half of the plots received those K rates annually and the other half only in the first three years, providing an opportunity to study the residual effect of applied K. Plant samples were taken at pod filling and at harvest. Soil cores were collected in 20 cm increments down to 80 cm deep at plant emergence, pod filling and after harvest. There was a residual effect of K, and 240 kg K2O/ha applied in a 3‐year term led to the same yield and K uptake as 80 kg ICO/ha applied annually for 3 years. Fertilized plants absorbed 160% more K than unfertilized ones, but soil exchangeable K accounted for less than 50% of plant uptake; therefore the exchangeable pool must have been replaced in time for soybean uptake. On the other hand, the K recycled from the plant to the soil was not found in the exchangeable form. There was evidence of K leaching deeper than 80 cm, and in addition, the K recycled from the plants may have turned into non‐exchangeable forms in the soil.

ISSN:0010-3624    

DOI:10.1080/00103628509367639

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Results from 2 pastoral field lime trials showed that liming reduced exchangeable Mg. This effect increased with increasing rate of lime and with time following lime application, and was greatest in the top 0–50 mm depth. Soil solutions, sampled 2 years after liming, showed that solution Mg increased in increasing rate of lime. This effect was greatest in the top 20 mm of soil.

ISSN:0010-3624    

DOI:10.1080/00103628509367640

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A field experiment was conducted on a Bradson gravelly loam (clayey, oxidic, mesic Typic Hapludult) at Fletcher, North Carolina, to determine the effect of timing and rate of N and rate of P and K fertilization on snap bean yield and grade, plant tissue nutrient concentrations, and residual soil test levels. Fertilizer treatments were arranged according to a sequential one‐factor‐at‐a‐time design and established as randomized blocks. Initial soil test levels by the Mehlich‐I extractant were 4 μg P/cc (very low) and 0.09 meq K/100 cc (low).

ISSN:0010-3624    

DOI:10.1080/00103628509367641

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The mean urease activities of the pasture and tillage counterparts of 10 soil series were 103 ± 44 and 75 ± 26 μg urea‐N hydrol. g‐1h‐1, respectively. Significantly (p<0.01) greater activity was recorded in the pasture variety of 8 series and in the tillage variety of 2 series. Multiple regression analysis showed that variations in the activities of the pasture soils (R2= 95.9%) and of 2 the tillage soils (R2= 97.3%) was attributable to variations in total‐N, unbuffered and pH‐dependent CEC, pH and silt, as well as C:N ratio in the case of the pasture group. The best‐fit regression for the latter soils was obtained when individual cations replaced CEC parameters (R2= 99.8%). Individual soil properties each accounted for a small proportion of the total variation. The results suggest that agricultural soils should be grouped by land‐use for best prediction of their urease activities. Differences between the activities of the pasture and tillage soils were highly correlated with the differences between their organic‐C and exchangeable Mg contents.

ISSN:0010-3624    

DOI:10.1080/00103628509367642

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Procedures for determining organic matter indirectly and directly in sludges are described. A good agreement between chromic acid oxidation and dry—combustion elemental analysis methods of determining organic‐C was observed. Sludge organic matter content was determined directly by loss‐on‐ignition by thermal analysis. An average C factor of 1.68 to estimate the organic matter from organic‐C, obtained by chromic acid oxidation method, was calculated for aerobically digested sludges.

ISSN:0010-3624    

DOI:10.1080/00103628509367643

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Simultaneous determination of anions in plant materials is needed. A simple and precise ion‐chromatographic (IC) method for ‐ O2‐4simultaneous determination of NO3, Cl‐, S. , and PO3‐4. in plant samples was developed. It involves extraction of these anions with deionized water and their simultaneous determination by IC. The averages of 10 plant samples by the IC method agreed closely with those obtained by the steam‐distillation method for NO‐3(0.158 vs 0.164%), titrimetric method using AgNO3and K2CrO4for Cl‐(1.22 vs 1.19%), and colorimetric heteropoly blue method for PO3‐4(0.335 vs 0.330%). The average SO2‐4S value of 10 plant samples by the IC method (0.067%) was somewhat lower than the corresponding value (0.075%) obtained by the reduction and colorimetric determination of methylene blue. The IC method is based on separation of the anions by a separator column containing Dionex low‐capacity anion‐exchange resin in the HCO‐3form and on converting the various anions to their corresponding acids by a suppressor column containing a strong cation‐exchange resin in the H+form. A solution of 3.0 mMNa2CO3+ 1.8 mMNa2CO3was used as the eluent, and electrical conductivity is used as the mode of detection. The method is precise and accurate and can detect as little as 0.1 mg/L of NO‐3‐N, Cl‐, SO2‐4‐S, or PO4‐3‐P in plant extracts. In addition to those anions, malic acid was separated and determined. With the IC method, the four anions indicated and malic acid can be determined simultaneously in 2 mL of plant extract in approximately 20 min.

ISSN:0010-3624    

DOI:10.1080/00103628509367644

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628509367635

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor