摘要:

A high nitrate pollution of groundwaters has been detected in recent years in many areas of southwest Spain where maize is cropped. This may be caused by the high fertilization level used in those areas. In this work, maize was grown consecutively for six years (1991–96) under Mediterranean management practices in the Guadalquivir River Valley (southwest Spain), using both a fertilization level widely used in the area (510 kg N ha‐1yr‐1) and one third of it. The effect of the reduced fertilization on crop development, yield parameters and kernel analysis was studied. Nitrate leaching for each fertilization treatment was also monitored, during one experimental year. Crop development was slightly poorer in the plot with reduced fertilization, but no differences in yield were found. The only effect on kernel composition was a higher nitrogen (N) concentration in the kernels of the plot with the higher fertilization level. The amount of N supplied by the reduced fertilization, together with the N in the irrigation water and from the soil mineralization, was enough to counterbalance the N removed by the crop in years of high production. Nitrate leakage was three times greater in the plot with the higher fertilization level than in the plot with reduced fertilization. A marked reduction in crop performance was observed in both plots in the first three experimental years. Some stabilization was observed afterwards.

ISSN:0010-3624    

DOI:10.1080/00103629809370158

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In Sweden the official method for estimating plant available potassium (K) is well calibrated to Swedish soils, but mainly provides information about exchangeable K. The objective was to evaluate a 0.01 M calcium chloride (CaCl2) solution (K‐CaCl2), with regard to its compatibility with standard laboratory procedures, and the relationship between the K‐CaCl2method and official Swedish methods depending on soil and fertilizing strategy. Soil was taken from long‐term field experiments with no K application or with applications of 160–240 K kg ha‐1yr‐1at Vojakkala, Ultuna, and Rådde. The soil samples, air‐dried or at field moisture content, were extracted by 0.01M CaCl2at two different soil:extractant ratios (1:2 and 1:10), and analyzed by inductively coupled plasma emission spectrometry (ICP) for K content. In Sweden, the official method for estimating plant available soil K is the ammonium lactate/acetic acid (AL) method and non‐exchangeable K is estimated in 2M HCl (K‐HCl). Amounts of K‐CaCl2from field‐moist and air‐dried soil were significantly affected by soihextractant ratio 1:2 or 1:10. This indicated that the same fraction of K in soil was not always extracted and that the amount depended on soil and fertilizing strategy. A soil:extractant ratio of 1:10 was preferable in order to get clear extracts. Air‐dried soil samples were most suitable for Swedish laboratory procedures. Overall, CaCl2extraction gave smaller amounts of K than AL and HC1 extraction. However, at Vojakkala and Radde treatments with K application considerably increased amounts of K‐CaCl2and K‐AL, compared with no K application. In treatments with no K application, amounts of K‐CaCl2and K‐AL were largest at Ultuna. There was a clear difference among sites in amounts of K‐ HC1. There seemed to be a good relationship between the K‐CaCl2and the K‐AL methods. However, the K‐CaCl2method extracted smaller amounts indicating that mostly K in soil solution was extracted. In Sweden, CaCl2could be a good complement to AL and HC1 extractable K and give a more complete description of K availability on different soil types and under different fertilizing strategies and could easily be incorporated into Swedish laboratory procedures.

ISSN:0010-3624    

DOI:10.1080/00103629809370159

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Field studies were made to determine the yield and quality of wheat at different landscape positions managed with uniform vs. variable rates of nitrogen (N). A moderately‐eroded wheat farm near Thana (Swat) was divided into four parallel transects which were further divided into two strips each. On one strip, fertilizer was applied at a uniform rate of 120 kg N ha‐1, and along the other strip, three different rates of N (80, 110, and 125 kg N ha‐1) were applied to match the crop productivity patterns. A basal dose of 90 kg P2O5and 60 kg K2O ha‐1was applied to the whole field. Soil profiles were described for the three different zones, i.e., low, medium, and high productivity zones. Soil in Zone I was Pirsabak, moderately deep variant, and in Zones II and III, Badwan soil series. Although uniformly fertilized strip (120 kg N ha‐1) received 40 and 10 kg N ha1more than Zone I and Zone II (variable management strategy), there were no significant differences in yield. The differences in three fertilizer management zones were due to differences in moisture content at sowing, infiltration rate, lime content, steepness, and soil depth. Test weight of wheat grains was not significantly affected. Protein content of wheat was significantly higher in variably fertilized strips than in uniformly treated strips. Based on these results, it is suggested that farms with spatially‐variable soils should be fertilized according to the crop productivity and soil fertility patterns.

ISSN:0010-3624    

DOI:10.1080/00103629809370160

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Ammonia volatilization from soils is a complex process generally associated with surface applied nitrogen (N) fertilizer. The effect of conventional tillage and no tillage on NH3volatilization was evaluated on cultivated corn (Zea maizeL.) field in Pampa Húmeda, Argentina. The objectives of this study were a) to determine the amount of N loss by volatilization (NH3) from urea fertilized soils under two different tillage systems (conventional and no tillage) and two different fertilizer application methods (surface and incorporated application) and b) to relate volatilization losses with environmental factors and biochemical and microbiological properties. This experiment was conducted on a Vertic Argiudoll with a silty clay loam texture in the Argentine Pampa. The site has been in natural grassland for 8 years prior was planted to corn. Following the fertilizer application for conventional tillage and no tillage systems, the daily volatilization loss of NH3on the fertilized plots was highest during the first three days. Higher losses of NH3occurred in the no‐tillage treatments, with 11.5% and 6.2% of N‐urea lost when the fertilizer was surface applied and incorporated, respectively. For conventional tillage, 8.6 % of the N was lost when the fertilizer was surface applied and 5.4% when the fertilizer was incorporated. Surface application of urea stimulated urease enzyme activity. An opposite effect was observed when the urea was incorporated. Environmental changes conditioned the availability of energy substrates for microorganisms, which resulted in different rates of intensity of biochemical reactions in the soil. Multiple regression equations showed differences between surface applied urea and incorporated urea treatments due to the latter avoiding the direct exposure of the fertilizer to atmospheric conditions.

ISSN:0010-3624    

DOI:10.1080/00103629809370161

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A regional survey was conducted in commercial orchards of pomegranate (Punica granatumL.) in order to develop diagnostic norms and for evaluation of yield limiting nutrients in low yielding orchards. The leaf nutrient status was interpreted using Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis (CND). The correlation structure among the nutrients was extracted by Principal Component Analysis (PCA). The departure of DRIS indices from their CND counterparts was relatively small and a highly significant positive correlation was obtained between DRIS and CND indices. The three principal components explained 59.5% of the variation in the high yielding population and the designated PCS were (N+S+Zn+Fe‐Mn‐), (N+P+Ca+Zn‐), and (K‐S+). Pomegranate is mainly grown on marginal soils with low fertility and hence more than two or three nutrients were found to be limiting yields. However, nitrogen (N) and zinc (Zn) were the most common yield limiting nutrients. The DRIS and CND indices for low‐yielding orchards are reported and discussed.

ISSN:0010-3624    

DOI:10.1080/00103629809370162

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An investigation was conducted on physico‐chemical properties of humic acids (HAs) in Venezuelan soils. The HAs were extracted by the NaOH method from a Banco‐Bajio‐Estero soil toposequence (local names for soils located at high, intermediate and low topographic levels), in the Venezuelan plains (Mantecal, Apure State). The extracted HAs were analyzed for elemental composition and characterized by fluorescence, Fourier transform infrared (FT‐IR) and electron spin resonance (ESR) spectroscopies. The results showed that free radical concentration of HAs increased from soils at the highest to soils at the lowest topographic position. High carbon (C), nitrogen (N), and carboxyl group contents, E4/E6ratio, aliphatic character and concentration of free radicals, and low oxygen (O) and phenolic hydroxyl group contents and total acidity were typical of HA from soils at the lower relief position. The FT‐IR spectra indicated that the HA from the soil at the lowest topographic position tended to have a slightly higher content of carboxyl groups than the HAs from soils at higher topographic levels. The observed fluorescence was attributed to the presence of condensed aromatic moieties and/or conjugated unsaturated systems of various complexity in the HA macromolecules.

ISSN:0010-3624    

DOI:10.1080/00103629809370163

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A field experiment was conducted on an Aerie Haplaquept soil to study the effect of phosphorus (P) deficiency in soil on the P nutrition and yield of five modern varieties of rice, viz., Purbachi, BR1, BR3, BR14, and BR29, popular with the rice farmers of Bangladesh. Soil‐available P in the different plots of the experimental field varied widely, from 2.8 to 16.4 ppm. This plot to plot variation in soil‐available P content resulted from differences in the total amounts (0 to 480 kg ha‐1) of P the plots had received over a period of 8 years in a long‐term P fertilizer trial conducted previously in the same field. Phosphorus deficiency in soil drastically reduced the grain yield of all the rice varieties. In severely P deficient plots, where soil‐available P was around 3 ppm, the yield was less than 1 ton ha‐1while in plots containing an adequate P level, i.e., >6 ppm, the yield was more than 41 ha‐1. Rice yield increased linearly with an increase in soil P content up to 6 ppm, and the highest grain yield for any variety, obtained at 6–7 ppm of soil‐available P leveled off at this point. Soil P deficiency not only decreased rice yield severely but also decreased P content in straw and grain drastically. However, differences among rice varieties were noted in P nutrition, particularly at low soil P levels. The rice varieties differed markedly also in respect of internal P efficiency. The BR29 showed the highest internal P efficiency both at low and high soil P levels. In all the rice varieties, internal P efficiency decreased with an increase in soil P levels.

ISSN:0010-3624    

DOI:10.1080/00103629809370164

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study was to determine the effect of soil amendments on the fractionation of selenium (Se) using incubation experiments under simulated upland and flooded conditions. The treatments were as follows: 1) control [soil + sodium selenite (Na2SeO3) (1 mg Se kg‐1)]; 2) control + calcium carbonate (CaCO3) (5 g kg‐1); 3) control + alfalfa (40 g kg‐1); and 4) control + CaCO3(5 g kg‐1) + alfalfa (40 g kg‐1). After a 90‐day incubation, soil was sampled and fractionated into five fractions: 1) potassium sulfate (K2SO4)‐soluble fraction (available to plants); 2) potassium dihydrogen phosphate (KH2PO4)‐exchangeable fraction (potentially available); 3) ammonium hydroxide (NH3H2O)‐soluble fraction (potentially available); 4) hydrochloric acid (HCl)‐extractable fraction (unavailable); and 5) residual fraction (unavailable). Compared with the control, CaCO3increased the K2SO4fraction at the expense of the NH3H2O fraction. Alfalfa increased both the K2SO4and residual fractions but reduced the KH2PO4and NH3H2O fractions. The CaCO3‐alfalfa treatment had a similar effect to the alfalfa treatment alone. The comparison between the upland and flooded conditions showed that the flooded condition generally increased the residual fraction and decreased the potentially‐available fractions. In general, CaCO3was a better amendment because it not only increased the available fraction but also maintained the potentially available fractions at a high level. The application of Na2SeO3and use of appropriate soil amendments can improve Se availability in soil.

ISSN:0010-3624    

DOI:10.1080/00103629809370165

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Plant residue compost, urban waste compost, farmyard manure, and peat can be used to ameliorate soil acidity. The diversity of these materials and their highly variable composition mean that their reliability in increasing the soil pH is uncertain because of lack of a method to test their acid ameliorating capacities. Incubation of a Spodosol from Sumatra, an Oxisol from Burundi and an Ultisol from Cameroon with 1.5% by weight of four composts, a farmyard manure and a sedge peat resulted in increased soil pH and decreased aluminum (Al) saturation measured at 14 days of incubation. The increased soil pH was directly proportional to the protons consumption capacity of the organic materials. This was measured by titrating the organic material from their natural pH values down to pH 4.0. This measure of acid neutralizing capacity provides a simple test method that was reliable across the variety of materials used. The final pH of the soil treated with organic material can be predicted with reasonable accuracy by determining the buffer characteristics of the soil and organic matter separately. The pH at the intersection of the two buffer curves predicts reasonably accurately the final pH of the treated soil. This suggests that a major mechanism of acid amelioration may be proton exchange between the soil and organic matter buffer systems. The increased soil pH was also directly proportional to the base cations [calcium (Ca), magnesium (Mg), and potassium (K)] contents of the added organic material. Such a relationship was presumably obtained because the base cations reflected the content of weak organic acid functional groups that are capable of binding protons and Al.

ISSN:0010-3624    

DOI:10.1080/00103629809370166

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Certain organic soil amendments have been found to ameliorate metal toxicity to plants. A study was undertaken to determine the effects of organic amendments on cadmium (Cd) and lead (Pb) distribution among soil fractions. Two soils (fine‐textured and coarse‐textured) were amended with five organic waste materials or commercial humic acid (HA) with and without 5 mg Cd kg‐1or 300 mg Pb kg‐1, incubated, and fractionated using a sequential extraction technique. The added Cd and Pb were found mainly in the organic matter (OM) fraction, although significant amounts were in the exchangeable (EXC) fraction for the sandy Norfolk soil. Spent mushroom compost (SMC) and HA lowered Cd in the EXC fraction for both soils and raised Cd in the OM fraction for the sandy Norfolk soil. The SMC and HA lowered Pb in the EXC and OM fractions and raised Pb in the manganese oxide (MnO), amorphous Fe oxide (AFeO) and the crystalline Fe oxide (CFeO) fractions. Poultry‐litter amendment caused higher Cd and Pb in the EXC fraction for the sandy soil. It was concluded from these studies that certain organic amendments like the SMC will lower Cd and Pb availability by redistribution the metals from the EXC and/or the OM fraction to less available fractions. Other amendments have little affect on Cd and Pb distribution, or for sandy soils, poultry litter can cause higher Cd and Pb in the more available fraction presumably due to the formation of soluble organic complexes.

ISSN:0010-3624    

DOI:10.1080/00103629809370167

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor