摘要:

A commonly used macro‐Kjeldahl digestion method for the determination of total N in soils containing N was modified for use with an electrically heated aluminum block containing 250‐ml volumetric tubes. The method was shown to recover quantitatively the15N added to soil as NO3‐, NO2‐, and plant material. When similar size soil samples were digested, the means and coefficients of variation for total soil N and15N recovery were comparable for this method and a macro‐Kjeldahl method employing 300‐ml flasks with electrically heated digestion stands. The method is intended as an alternative for laboratories that desire to minimize sampling error by use of a macro‐Kjeldahl rather than a micro‐Kjeldahl digestion but do not have suitable macro‐Kjeldahl digestion stands and flasks for analysis of N‐labeled soils. The electrically heated aluminum block results in uniform heating of digests, conservation of laboratory space, and ease of handling of samples when compared with ordinary macro‐Kjeldahl equipment.

ISSN:0010-3624    

DOI:10.1080/00103628509367583

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Four exchangeable cations (Ca, Mg, Na and K) were determined in aqueous and alcoholic NH4Cl soil extracts using ICPES.

ISSN:0010-3624    

DOI:10.1080/00103628509367584

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Zambia possesses tremendous potential in implementing multiple cropping systems. To utilize this potential, an expansion of irrigated crops grown during the dry season (May to October) must be achieved. However, this implies the need for a more rational and efficient use of water and fertilizer. A two‐year study was, therefore, conducted to find out the response of wheat(Triticum aestivumL.) to different irrigation regimes, different rates and methods of placement of urea N. Differential irrigation commenced after tillering either on a weekly, every two week, or every three week basis with irrigation water applied at 70, 60, and 50 percent of the total pan evaporation during the whole irrigation interval, respectively. Maximum yields were obtained with weekly irrigation and split application of urea at rates of 50 kgN ha‐1at seeding and minimum 25 kgN ha‐1topdressed at tillering. Of the four methods of N fertilizer placement (broadcast or broadcast and incorporation before seeding, side‐banding at seeding and broadcast two weeks after seeding) maximum yields were obtained either by broadcasting the initial portion of the fertilizer two weeks after seeding, or by broadcast and incorporation prior to seeding.

ISSN:0010-3624    

DOI:10.1080/00103628509367585

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The influence of different levels of irrigation on the grain yield of wheat was studied in a two year experiment at the National Irrigation Research Station at Nanga. The irrigation schedules were irrigation every week, every two, and every three weeks at a rate of 70, 60 and 50 percent, respectively, of the total class A pan evaporation during the whole irrigation interval. Apparent water use by wheat increased with shorter irrigation intervals. However, none of the above schedules was deemed satisfactory for obtaining maximum wheat yields.

ISSN:0010-3624    

DOI:10.1080/00103628509367586

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Grain deficits frequently occur in the Southeastern Atlantic Coastal Plain because erratic rainfall patterns and soil properties often limit corn (Zea maysL.) yields, however, harvesting corn for silage may enable farmers to produce a second grain crop during the same calendar year. Effects of row spacing, plant population, and fertilizer program on yield, quality, and mineral concentrations of corn silage grown with irrigation on Typic Paleudult soils were therefore investigated. Two plant population treatments which averaged 7.0 and 10.1 plants m‐2were evaluated withtwofertilizer programs that differed in N, N and K, and N, P, and K in 1980, 1981, and 1982, respectively. Each plant density by fertilizer combination was evaluated in single rows spaced 96 cm apart and in twin rows which approximately doubled the intrarow plant spacing. Plot size for the 2×2×2 factorial experiment ranged from 30 to 44 m2. Yield, quality, and mineral concentrations of corn silage grown in single rows spaced 96 or 75 cm apart and twin rows were also evaluated in large (185 m2) plots under center pivot irrigation during 1981 and 1982.

ISSN:0010-3624    

DOI:10.1080/00103628509367587

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Field experiments were conducted to evaluate N and K fertilization rates, fertilizer placement, and water management practices for fresh‐market tomato (Lycopersicon esculentumMill.) production in the Southeastern Atlantic Coastal Plain. Plant nutrient status, fruit yield, and fruit firmness after 12. to 15 days of storage at 20C were evaluated. Nitrogen rates of 130 or 200 kg/ha significantly increased yield of extra‐large and large fruit compared to the 67 kg/ha N rate. There was no significant difference in yield response among K rates of 46, 140, or 280 kg/ha. Marketable fruit yields for banded or broadcast placement of fertilizers beneath the black polyethylene mulch were not significantly different. Trickle irrigation did not cause extensive nutrient leaching or induce a “soft‐fruit”; storage syndrome. The ‘Tempo’ cultivar yielded significantly more extra‐large fruit with or without irrigation. However, after 12 to 15 days at 20C, internal firmness of physiologically similar fruit was lower for ‘Tempo’ than for the ‘Flora‐Dade’ cultivar. These results provide management guidelines for intensive tomato production in the Southeastern Atlantic Coastal Plain.

ISSN:0010-3624    

DOI:10.1080/00103628509367588

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

In the past several years many scientists, consultants and growers in northern Idaho and eastern Washington have noticed a decline in the pH of agricultural soils. The purpose of this study was to compile and generate data for the determination of the causes, rate and magnitude of the pH decline in the region. Soil pH records from the past 40 years were collected from the soil testing laboratories at the University of Idaho and Washington State University. An intensive field pH survey was conducted in northern Idaho from 1982–84 and virgin soil samples were acidified under laboratory conditions.

ISSN:0010-3624    

DOI:10.1080/00103628509367589

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Ryegrass was grown in 12 soils at 10 and 25°C in a pot trial carried out under controlled climate conditions. Adsorbed sulphate determinations were carried out on the soils both before and after the trial using 2 related methods; 1/2 h extraction with 0.04MCa(H2PO4)2followed by charcoal treatment and reductive distillation and 16 h extraction with 0.04MCa(H2PO4)2followed by reductive distillation with no charcoal pretreatment. Total DM yield and S‐uptake at the two temperatures were correlated with the two measures of adsorbed sulphate employed. Estimates of the apparent net mineralisation of organic S during the trial were also made on the basis of each set of adsorbed sulphate measurements and correlated with ester‐S, C‐bonded S and total organic S levels in the soils and with the mean levels of sulphatase activity and microbial respiration recorded during the trial.

ISSN:0010-3624    

DOI:10.1080/00103628509367590

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Soybean (Glycine maxL. Merr.) cultivars differ in their root morphology and their nutrient uptake capabilities. The relation between root growth, P and K uptake, and grain yield was investigated using eight cultivars grown in the field on Raub (Aquic Argiudoll) silt loam which received 49 kg P/ha and 93 kg K/ha. Hobbit (maturity group III, determinate) was among the highest in grain yield, P and K uptakes, and root system length. However, this cultivar was intermediate in its relative efficiency to utilize P and K to produce grain yield; among the most efficient cultivars were Asgrow 3127 (maturity group II) and Williams‐79 (maturity group III). The hay cultivar, Wilson‐6, was the least efficient. It was concluded that even though grain yield was correlated with nutrient uptake, selection for higher yields was not necessarily a selection for higher efficiency in utilization of fertilizer for grain production.

ISSN:0010-3624    

DOI:10.1080/00103628509367591

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628509367582

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor