ISSN:0010-3624    

DOI:10.1080/00103629409369107

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The high P fixation capacity of soils rich in x‐ray amorphous minerals has been well documented. Some Andisols in central Guatemala which have received additions of volcanic ash have extraordinarily high extractable P levels with acidic extractant. These ash materials have low fixing capacities but they weather rapidly. This study examined the relationship between different soil P tests on soils from Guatemala. The study area has a strong volcanic influence. Some volcanos are still active, from which the ash being deposited is rich in apatite. Age and composition of the parent materials exert the strongest influence on soil properties. Thirty‐two soils from the southern part of Guatemala were divided according to their classification and soil properties. Chemical methods (Bray I and Mehlich I) were compared to two other soil test techniques (Pi strip and Resin‐strip). Phosphate retention characteristics were also measured. In general, very good correlations were found between all methods on soils that do not have any recent ash influence. On soils with ash deposition containing apatite, Bray I and Mehlich I readily dissolve this Ca‐P compound and gave exaggeratedly high P values. The Pi strip and Resin‐strip methods were more appropriate in estimating available P in all soils irrespective of their properties, suggesting that either of these two methods could be adopted for the purpose of P fertilizer recommendations. The thickness and weathering status of the recent ash deposits vary with the catenary sequence down the volcano and determine soil P fertility management. Phosphorus fixation was lower on soils being rejuvenated by ash depositions, but water retention properties were reduced. On soils with a buried Andisol covered by fresh material on the surface, specific soil management strategies should be adopted. The presence of apatite in volcanic ash influencing soil P availability has not been described in the literature.

ISSN:0010-3624    

DOI:10.1080/00103629409369108

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

From November 1991 until January 1992, a 956 km2area of the loamy sand to sandy loam region of West‐Flanders (Belgium) was sampled for residual soil nitrate,i.e.the amount of nitrate nitrogen in the soil profile at the end of the growing season. In total, 296 soil samples were taken to a depth of 90 cm (in layers of 30 cm) on arable land only. On basis of the rate of the mineral nitrogen losses occuring during this extended period, all residues present on the date of 21 November 1991 were estimated. This date corresponded with the start of the sampling campaign and is close to the end of the growing season. The residues were lognormally distributed around a mean of 177 kg NO3‐‐N/ha with a minimum of 24 and a maximum of 881 kg NO3‐‐N/ha. Classifying the residues into groups according to the preceding crop, the lowest residues appeared after beets (a median of 59 kg NO3‐‐N/ha). Between cereals, maize, potatoes, and vegetables, no significant differences were found. Each of these four groups had a median residue of about 170 kg NO3‐‐N/ha. The high amounts found after cereals were due to a continuing mineralization of the soil organic matter during the three months between harvest and sampling time. This residual soil mineral nitrogen must be limited to minimize the NO3‐‐N drainage losses during winter which otherwise enhance the nitrate concentration in ground and surface waters.

ISSN:0010-3624    

DOI:10.1080/00103629409369109

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effect of varying phosphorus (P) supply on the growth, yield, leaf abnormalities, and nutrient composition was investigated for three lettuce cultivars (Chaparal, Wintercrisp, and Robinvale) in sand culture and soil. The leaf P content for optimum yields varied between 0.40 and 0.90% while higher than 0.90% P seemed to cause leaf abnormalities in Chaparal and Winter‐crisp. With high P supply, more calcium (Ca) was necessary to overcome the detrimental effect of P. In soil, maximum yields were obtained with a P supply level of 540 mg/kg P, while higher levels caused yield reductions. Soil analysis at the end of the experiment showed that a soil P content of 250 mg/kg P (Bray II) was associated with the best yield. When additional Ca was supplied to the soil, yield reduction due to high P supply was reduced. The leaf abnormalities which coincided with the high P supply were similar to those which have previously been described for auxin‐type herbicide damage on lettuce.

ISSN:0010-3624    

DOI:10.1080/00103629409369110

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The expert system nitrogen (N)‐index calculates N fertilizer recommendations for arable crops in temperate regions. The knowledge base of N‐index leans on different fundamentals, such as the measurement of the mineral N stock in soil in spring, the calculation of the evolution of the mineral N content in time and depth in the soil profile as well as the crop response to N fertilizer rates. The calculations with the empirical and theoretical founded knowledge base results in a N‐index value, which is subdivided into different values each representing a major point of vue to know the N availability for the growing crop. Since the introduction of the N‐index expert system in Belgium and the northern part of France in 1979, many crops were added to the knowledge base. The number of samples and correlated analysis data increased, making it possible to review accurately the mineral N stock in the soil after the winter period as a function of many factors,e.g.previous crop and organic fertilizer application.

ISSN:0010-3624    

DOI:10.1080/00103629409369111

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Both nutrient concentrations and nutrient ratios of plants have been associated with crop seed yields, but research examining their relative correlation to yield is scarce. Furthermore, research comparing nutrient diagnoses by the modified‐diagnosis and recommendation integrated system (M‐DRIS) against diagnoses resulting from use of M‐DRIS concentration means as critical nutrient levels (CNL's) is lacking. Consequently, a soybean[Glycine max(L.) Merrill] cultivar by phosphorus (P) by potassium (K) by limestone soil fertility field study conducted on a Cresco loam (fine‐loamy mixed, mesicTypic Argiudoll)was used to determine: (i) whether plant nutrient concentrations or ratios better accounted for differences in soybean seed yield; and (ii) whether diagnostic systems that use nutrient concentrations or nutrient balance are more accurate in diagnosing soybean P and K status. Correlation analyses demonstrated that both nutrient concentrations and nutrient ratios were related to yield, but partial correlations showed that concentrations explained more variability in yield than did ratios. Partial correlations also indicated that most nutrient ratios were correlated to yield simply because one of the nutrients in the ratio was related to yield. Potassium diagnoses by M‐DRIS were superior to those for the CNL when M‐DRIS concentration means were used as CNL's. However, these differences could be attributed to factors other than nutrient balance versus concentrations.

ISSN:0010-3624    

DOI:10.1080/00103629409369112

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Seedlings ofCatharanthus roseus’Grape Cooler’ transplanted into 120‐cm3cell packs of three commercial potting media were fertilized at each irrigation in flood and drain trays with commercial 20N‐4.4P‐17K fertilizer at concentrations of 50, 150, or 250 ppm nitrogen (N). Media samples were obtained 2, 3, 4 and 5 weeks post transplant. The contents of four cells from each of two replications were airdried, mixed, and sifted to pass a 2 mm sieve. Concentrations of calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P), ammonium (NH4+), and nitrate (NO3‐) were measured in Spurway (SPUR) and Saturated Media (SME) extracts. Electrical conductivity (EC) was measured in SME extracts. Leaf samples obtained four weeks post transplant were analyzed for all essential elements. Highly significant correlations were obtained for nutrient concentrations in SME and SPUR, but the coefficient of determination (r2) for linear regressions ranged from 0.34 for Ca to 0.77 for NH4+. Trends over time for increasing concentrations of Ca and Mg were detected in SME, but not SPUR. SME and SPUR indicated generally similar trends for NH4+and NO3‐. Both media extracts were correlated with plant tissue for P, but not other elements. Media EC increased with time and with increasing fertilizer concentration. EC in all media fertilized with 250 ppm N exceeded 4.5 dS/m at the final harvest. Plant growth responded positively to increasing fertilizer concentration to 150 ppm N in two media, probably due to increased accumulation of both N and P. Decreased growth at 250 ppm was related to high EC.

ISSN:0010-3624    

DOI:10.1080/00103629409369113

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In the paper, five methods of plant sample preparation (microwave digestion with nitric acid, and nitric acid and hydrogen peroxide; solubilization with diluted hydrochloric acid; mineralization in mixture of nitric, sulphuric, and perchloric acids; and dry way mineralization in muffle furnace) for determination of calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P), sodium (Na), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) were compared. Approximately equal results were obtained for all the ways used. The only exception was solubilization at which incomplete extraction of Fe and expected impossibility of diluted acid to act on phosphate groups of organic compounds were observed. The speed of sample preparation and the values of blanks were significantly in favour of microwave digestion of samples.

ISSN:0010-3624    

DOI:10.1080/00103629409369114

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

For two soil types, loamy degraded chernozem and silty loam, the conversion equations for phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) determined after extraction with Mehlich 1‐, 2‐, and 3‐, and CaCl2‐extractants, for K after extraction according to Schachtschabel‐, and P according to Egner‐, Bray‐, and Olsen‐methods were found out. The results show that for most nutrients, it is possible to use for data‐conversion 1st order equation common for both soil types. For some nutrients and extractions methods, different conversion equations seem to be necessary. Close correlations between organic matter and total carbon (C) (r = 0.929***) and hydrogen (H) (r = 0.912***) and between total C and H (r = 0.857***) were also confirmed. Very close relations were found for pH determined in CaCl2‐ and KCl‐extracts (r = 0.991***). For both soil types, similar curves of relations of soil pH as the functions of Ca‐content (according to Mehlich 1‐, 2‐, and 3‐methods) with typical tendency to saturation were observed. Effects of K, Ca, Mg, pH, and soil organic matter on Mehlich 1‐, 3‐, and CaCl2‐extractable P were studied too.

ISSN:0010-3624    

DOI:10.1080/00103629409369115

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Field experiments were conducted to predict optimum tissue sulphur (S) concentration, nitrogen:sulphur (N:S) ratio in leaf tissue and S levels for maximum grain yields of soybean cultivar PK‐327. Various S levels significantly increased the S and N contents in 50‐day‐old plants, straw and soybean grains. Test weight of soybean grains was also increased. N:S ratio wider that 16.0 in soybean leaves of 50‐day‐old plants was considered to indicate S starvation. Leaf N:S ratio of 10.83 produced maximum soybean grain yield. Among ammonium sulphate, superphosphate, and elemental S tried as a source of S, ammonium sulphate was found to be the best source of S for soybean. It is recommended that soil testing programmes should include testing for S status so that only optimum levels of S are applied as higher levels of applied S appear to be luxuriantly consumed.

ISSN:0010-3624    

DOI:10.1080/00103629409369116

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor