摘要:

Glasshouse experiments were conducted at the Newe Ya'ar Research Center in the winter seasons of 1992/93 and 1993/94 to examine a phosphorus/ potassium (PK) fertilizer for cucurbit crops. Monopotassium phosphate [(MKP), KH2PO4] was found to be very effective as a P and K source for cucumber (Cucumis sativusL.) and muskmelon(Cucumis meloL.) plants grown in soilless container conditions. The efficiency of MKP was essentially not different from that of the combination of phosphoric acid (H3PO4) and potassium chloride (KCl) which is widely used in the commercial production of vegetables. Appropriate fertilization of cucumbers with MKP in 1992/93 affected late‐season yield more than early‐season yield. Deficiency of P and K in Gala muskmelon inhibited vegetative growth and decreased yield. The reduced yield resulted from both less fruit‐setting and smaller fruit size. The MKP rates required by cucumber plants in 1993/94 depended primarily on growth medium composition. Generally, plants grown in inert tuff (volcanic gravel) and sandy media responded more significantly to MKP than did those grown in media rich in organic matter. There are at least three reasons for preferring the use of MKP, first it is much safer to handle than is H3PO4, second it is highly soluble and can be easily incorporated in fertigation systems, and third it has a high PK content.

ISSN:0190-4167    

DOI:10.1080/01904169709365254

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Field studies were conducted at Bouctouche Research Farm in New Brunswick, Canada to determine the effect of zinc (Zn) and nitrogen (N) on silage corn. Soils at these sites are coarse texture loamy sand with pH values of 6.0–6.3 and organic matter content of 2.6 to 2.7 mg·g‐1. In Experiment 1, Zn application at 0.5 to 1.0 kg·ha‐1foliar or 10 to 20 kg·ha‐1soil applied significantly increased the silage corn dry matter yield. Leaf Zn levels of 8.8 to 10.1 mg·kg‐1and available soil Zn at 0.8 mg·kg‐1in the check treatments were related to Zn deficiency in corn. No response to Zn was noted in Experiment 2 and this was associated with leaf Zn levels of 15 to 16 mg·kg‐1in the control treatment. In the Zn x N field study, a significant dry matter yield response to N and Zn was obtained. Nitrogen applications with or without added Zn increased leaf Zn. Leaf Zn increases were highest at the highest rate of added N. Corn leaf Zn levels at 9 mg·kg‐1were associated with lower yield. Zinc deficiency in corn can be controlled by 1 kg Zn ha‐1foliar or 10 to 20 kg Zn ha‐1soil applied.

ISSN:0190-4167    

DOI:10.1080/01904169709365255

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A 2‐yr study was conducted to evaluate the effect of within‐row spacing and nitrogen (N) fertility on sweetpotato [Ipomoea batatas(L.) Lam.] yield and quality. Conducted in North Alabama on a Hartsells fine sandy loam (fineloamy, siliceous, thermic Typic Hapludult), the study consisted of four replications of a factorial arrangement of four within‐row spacings (15, 20, 25, and 30 cm) and 4 N fertility rates (0, 36, 72, and 108 kg N/ha). Nitrogen fertilization did not affect yield or quality of harvested storage roots and there was no significant interaction between row spacing and N rate in either year. In 1994, greatest total yield ofsweetpotatoes occurred with the narrowest within‐row spacing (15 cm), but in 1995 within‐row spacing did not affect total yield. In 1994, as within‐row spacing increased, yield of Jumbo sweetpotatoes increased.

ISSN:0190-4167    

DOI:10.1080/01904169709365256

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The effects on two‐week‐old plants of a salt‐tolerant line (Euroflor) and a salt‐sensitive (SMH‐24) line of sunflower, of varying sodium/calcium (Na/ Ca) ratios in a saline growth medium were assessed after three weeks growth in sand culture under greenhouse conditions. The different Na/Ca ratios of the salt treatment were 36.5, 74.0, and 149, at a constant concentration of 150 mol m‐3NaCl. Euroflor was superior to SMH‐24 in fresh and dry matters of shoots and roots at varying external Na/Ca ratios. The leaf Na+concentration in SMH‐24 increased consistently with increase in external Na/Ca ratio, whereas that in Euroflor remained almost unaffected. Although leaf chlorine (Cl‐) was significantly greater in SMH‐24 than Euroflor, there was no effect of decreasing Ca2+concentration of the saline growth medium on the leaf Cl‐concentrations of both lines. The lines did not differ in K+, Ca2+or Mg2+concentrations of both shoots and roots. The leaf K/Na and Ca/ Na ratios, K versus Na selectivity were considerably higher in Euroflor than in SMH‐24. The lines also did not differ in leaf water potential and gas exchange and these variables were not affected due to decreasing Ca2+concentration of the saline growth medium. Stomatal conductance and transpiration remained unchanged in Euroflor, whereas those in SMH‐24 decreased significantly at the highest external Na/Ca ratio. Euroflor had significantly greater stomatal conductance and transpiration than those of SMH‐24 at almost all external Na/Ca ratios, whereas the reverse was true for water use efficiency. It was established that Euroflor was tolerant to low Ca2+concentrations of the saline growth medium as compared with SMH‐24. This was mainly attributable to accumulation of relatively low Na+and Cl‐in the leaves, and maintenance of high leaf K/Na and Ca/Na ratios and K versus Na selectivity in Euroflor.

ISSN:0190-4167    

DOI:10.1080/01904169709365257

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Sodium arsenite (NaAsO2) was applied to twoVitis viniferavarieties, Aledo and Italia, for three years at a concentration of 1.25 kg NaAsO2100 L‐1applied by spraying or by direct application with a paint brush. Accumulation of arsenic (As) in leaves and fruits during these three years was not detected. Spraying resulted in the highest levels of As in the leaf with the concentration decreasing as the vegetative cycle advanced. The amount of As that accumulated in the plant was related to the proximity of the As application to bud break. The As levels detected in the eatable part (table grape) never reached concentrations that would be considered harmful to human beings.

ISSN:0190-4167    

DOI:10.1080/01904169709365258

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Gaseous nitrogen (N) loss from winter wheat(Triticum aestivumL.) plants has been identified, but has not been simultaneously evaluated for several genotypes grown under different N fertility. Two field experiments were initiated in 1993 and 1994 at the Agronomy Research Station in Stillwater and Perkins to estimate plant N loss from several cultivars as a function of N applied and to characterize nitrogen use efficiency (NUE). A total of five cultivars were evaluated at preplant N rates ranging from 30 to 180 kg·ha‐1. Nitrogen loss was estimated as the difference between total forage N accumulated at anthesis and the total (grain + straw) N at harvest. Forage, grain, straw yield, N uptake, and N loss increased with increasing N applied at both Stillwater and Perkins. Significant differences were observed among varieties for yield, N uptake, N loss, and components of NUE in forage, grain, straw, and grain + straw. Estimates of N loss over this two‐year period ranged from 4.0 to 27.9 kg·ha‐1(7.7 to 59.4% of total forage N at anthesis). Most N losses occurred between anthesis and 14 days post‐anthesis. Avoiding excess N application would reduce N loss and increase NUE in winter wheat varieties. Varieties with high harvest index (grain yield/total biomass) and low forage yield had low plant N loss. Estimates of plant loss suggest N balance studies should consider this variable before assuming that unaccounted N was lost to leaching and denitrification.

ISSN:0190-4167    

DOI:10.1080/01904169709365259

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The effect of prolonged sulfur (S) deficiency on photosynthesis and S‐containing compounds in leaves of rapeseed(Brassica napusL.) plants, grown in nutrient solution, was studied under greenhouse conditions. The rate of photosynthetic activity and stomatal conductance of water and CO2in treated plants decreased significantly after 3 months of treatment. The total chlorophyll content decreased after one month of S deprivation, after which it remained constant. The total S. content and both the water‐soluble and non‐protein soluble S fractions in the leaves showed a marked decrease. Whereas, the total protein soluble S remained unaffected during the period of observation. In the treated plants, the content of two major S compounds, e.g., cysteine and glutathione, were as a result of deprivation, although in the control it showed a trend to increase. Sulfur deficiency also decreased appreciably the activity of ATP sulfurylase. After the three‐month period of S deprivation, this enzymatic activity was about four times lower than that in the control plants. The data reported in this paper suggested that plants grown under S deficiency were capable of adjusting their S metabolism to maintain a sufficient protein and glutathione synthesis by lowering their photosynthetic activity.

ISSN:0190-4167    

DOI:10.1080/01904169709365260

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169709365261

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169709365243

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor