摘要:

Application of clear plastic mulch with or without N fertilizer did not significantly increase (P > 0.05) yield of cos lettuce(Lactuca sativaL. cv. Paris Island), grown in Fall in a greenhouse in the Mediterranean mountains. Yield ranged from 31 to 38 kg/50 heads. Leaf NO3‐N and total P levels were higher in mulched than unmulched plants, and in fertilized than in unfertilized plants, and always above the sufficiency level in all treatments. Soil levels of NO3‐N were higher under mulched than unmulched plots, and under fertilized than unfertilized plots, which had more than 50 ppm NO3‐N at harvest. This indicates ample supply of N and thus explains the lack of response to added N. It may be concluded that in mild climates and on soils with adequate N, lettuce will not respond to the use of clear mulch and N fertilizer.

ISSN:0190-4167    

DOI:10.1080/01904169109364261

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The reduction capacity for ferric chelates ofGeum urbanumL. showed a marked increase when plants were grown under conditions of iron‐shortage. Ferric ethylenediaminetetraacetate (FeEDTA) was reduced with a pH optimum between 5 and 6. The reaction exhibited a low substrate affinity with a Kmmuch higher than the expected concentration range of soluble iron in the soil. Analysis of the saturation plots conform to Michaelis‐Menten kinetics. Both Vmaxand Kmvalues varied to a broad extent with changing assay and plant culturing conditions. Ferricyanide was reduced at significantly higher rates than FeEDTA and inhibited the reduction of FeEDTA compete‐tively. The kinetic characteristics of iron reduction by plants will be discussed in terms of ecological significance as part of an adaptation to the soil conditions.

ISSN:0190-4167    

DOI:10.1080/01904169109364262

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Absorption and translocation of foliar applied15N labeled S‐tetrahydrotriazone (triazone), as compared to other N forms, was evaluated in tomato plants. Triazone‐N was taken up into leaf tissue in quantities similar to urea, ammonium, and nitrate‐N when applied at a N concentration of 0.35% w/v. Although >40% of the15N label was exported from the treated leaf after 7 days, nearly 50% of the translocated triazone15N label accumulated in non‐treated leaf tissue as compared to only 10% or less for the other N sources. The largest percentage of the translocated urea‐, ammonium‐, and nitrate‐15N label accumulated within developing fruit tissue. Multiple (3) foliar applications of triazone and urea at concentrations of 0.94% or higher and 1.0% N (w/v), respectively, enhanced both leaf and fruit tissue N concentrations. No growth responses to foliar applied N were observed.

ISSN:0190-4167    

DOI:10.1080/01904169109364263

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Bell pepper (Capsicum annuumvarannuumL.), cv Pip, transplants were established at 31 and 46 cm in‐rows on bare soil and drip irrigated on a twice weekly schedule. A base rate of fertilizer was applied either in one preplant application or in two (preplant and first flower set) or three (preplant, first flower set, after the midseason harvest) split applications. Additional fertilizer was applied in excess of the base rate on a predetermined schedule or after significant yield decline ('as needed'). Concentrations of 12 elements in leaf and fruit tissues were determined throughout the growing season. The three‐split application of the base rate of fertilizer increased total yield. Plants spaced at 46 cm had increased total and marketable yield in one year. Interactions of fertilizer treatment and plant spacing did not affect total yield. In one year when additional fertilizer was applied ‘as needed’, plants spaced at 31 cm produced more marketable yield than plants spaced at 46 cm. Nutrients in leaves and fruit did not respond to fertilizer treatment or spacing. In leaves and fruit, concentrations of elements increased, decreased/or stayed the same in both years. For leaves, exceptions were Cu, Mn, and N. For fruit, exceptions were Al, Fe, K, and N. A base level application of fertilizer applied preplant was sufficient to support marketable fruit production.

ISSN:0190-4167    

DOI:10.1080/01904169109364264

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Aluminum stress did not reduce root and shoot growth significantly, nor were the pooled Al stress x cultivar interactions significant. Cultivars differed significantly in mean shoot and root vigor in nutrient solutions but not in soil. R‐esponses in soil were only weakly correlated with responses in nutrient solutions. Am 312 and Appalow had the lowest relative weight values (dry weight stressed/dry weight unstressed) in both media and Interstate and Interstate 76 the highest. Interstate 76 exhibited a significant positive response (5% level) to Al when evaluated in nutrient solutions.

ISSN:0190-4167    

DOI:10.1080/01904169109364265

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Alyssum bertoioniiDesv., a crucifer which grows only in Tuscany on serpentine soil, is characterized by high Ni concentration in its leaves and a high tolerance to this element. In this research, the Co and Zn tolerance ofA. bertoloniihas been tested and compared with that of Ni. Although the Zn concentration in the serpentine soil on which the plant grows is lower than that of Co, root growth showed no significant difference for these two elements. In excised roots, on the other hand, Co and Zn compete with Ni uptake and accumulation. Seedlings do not show any inhibition in the translocation of these three elements. They are all rapidly carried to and accumulate in the shoots, but the uptake and traslocation of Zn does not show the saturation trend found for Ni and Co. The same gel filtration fractions contain the three elements in association with malic acid, involved in Ni tolerance.

ISSN:0190-4167    

DOI:10.1080/01904169109364266

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Acid, sandy soils selected for blueberry production are usually deficient in plant available phosphorus. Fertilizer addition at planting has not been a recommended practice. This research was designed to evaluate potted blueberry(Vaccinium asheiReade) plant growth response to P applied at establishment and interacted with N applied during the growing season. Four liter containerized ‘Tifblue’ rabbiteye blueberry plants were transplanted into 4.4 kg of 1:1 v/v loamy sand:peat mixture in an 8‐liter container. Preplant P was incorporated into the mixture at 0, 20, 40, 60, and 80 kg/ha rates. Nitrogen was split‐applied post‐plant four times at 60‐day intervals beginning 30 days after blueberry bushes were transplanted. Total N rates were equivalent to 0, 112, 224, or 336 kg/ha. Plants were harvested 270 days after transplanting. Phosphorus at the 60 and 80 kg/ha rates increased plant growth 40 and 31%, respectively. Plant growth responded linearly to increasing N rate. Leaf and stem weight increases contributed to this linear response while root weight was not affected by fertilizer N. Total plant dry weight was increased by N rates at the 60 and 80 kg/ha P levels. Phosphorus applications increased leaf P levels, but did not increase soil test P. Leaf redness, caused by cool temperatures, was reduced by high N rates. The optimum P rate for fertilization of the soilrpeat mixture in the planting hole under conditions of this experiment was the equivalent of 60 kg/ha.

ISSN:0190-4167    

DOI:10.1080/01904169109364267

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Many of the poorly drained clayey soils of the Mississippi River delta region in Arkansas are used for soft red winter wheat (Triticum aestivumL.) production. Oftentimes, excessive rainfall occurs between the last N application and physiological maturity, resulting in soil conditions conducive to denitrification. Studies were conducted in 1989 and 1990 to evaluate late N applications on five wheat cultivars on a Sharkey silty clay (very fine, montmorillonitic, nonacid, thermic, Vertic Haplaquepts) at Keiser, AR. A linear‐move irrigation system was used to maintain excessive soil moisture conditions throughout the spring growing season to best insure denitrification conditions. After the recommended spring N was applied, N as urea was applied at rates of 0, 34, and 68 kg ha‐1at growth stage (GS) 9 in 1989 and GS 10 in 1990. Ammonium nitrate was also evaluated at the 34 kg N ha‐1rate. Grain yield, yield components, whole‐plant N concentration, grain N content, and whole‐plant N uptake were evaluated. Grain yield increased each year with late N applications. The optimum N rate was 34 kg ha‐1with no difference between the N sources, urea and ammonium nitrate. The yield component accounting for this grain yield increase were kernels per spike in 1989 and kernel weight and kernels per spike in 1990. Whole plant N concentration increased each year and grain N content increased in 1990 with the late N application. The N sources affected N nutrition similarly.

ISSN:0190-4167    

DOI:10.1080/01904169109364268

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In a solution culture experiment, the growth and nutrient uptake of wild oat plants(Avena fatuaL.) was compared with that of cultivated oat plants(Avena sativaL. cv. Pennlo) at both low (5 μM P) and high (100 μMP) levels of phosphate. Solution phosphate depletions and plant growth variables were measured through daily solution sampling and destructive tissue harvests. Wild oat produced more root mass and accumulated P more rapidly than the cultivar in both low and high P levels. Wild oat plants also produced significantly more dry matter for a given accumulation of P than the cultivated oat plants in both low and high P solutions. We conclude that wild oat is likely to be competitively superior to the Pennlo cultivar under conditions of moderate P limitation due to its greater allocation of dry matter to roots and higher P use efficiency.

ISSN:0190-4167    

DOI:10.1080/01904169109364269

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Grain sorghum (Sorghum bicolorL. Moench) production commonly occurs on poorly drained clayey soils of the Mississippi River delta region inArkansas. Raised, wide seedbeds may improve grain yield and fertilizer N efficiency for narrow‐row sorghum production on these soils. The influence of individual row positions on raised, wide seedbeds was compared to conventional flat seedbed for grain yield, yield components, dry weight, and N uptake. A 193‐cm wide and 15 cm high crowned seedbed (CB) was compared to the flat seedbed (FB) in 1987 and 1988 on a Sharkey silty clay (very fine, mont‐morillonitic, nonacid, thermic, Vertic Haplaquepts) at Keiser, AR. Three rows were planted on each seedbed treatment; one in the middle of the bed and one row 48 cm to each side of the row in the middle. Nitrogen rates of 0, 56, 112, and 168 kg/ha were applied at planting. In addition, two split applications at the 168 kg/ha N rate (56 kg N/ha at planting and 112 kg N/ha at either four‐leaf or eight‐leaf growth stage) were evaluated. Each row position was evaluated for grain yield, yield components, plant dry weight, and N uptake. Whole plant samples were collected at the anthesis and physiological maturity growth stages. The field average grain yield was higher on the CB each year regardless of N rate applied at planting. This yield increase on the CB was related to the row on the top of the CB yielding more than the equivalent row on the FB. The responses of plant dry weight at each growth stage, N uptake at each growth stage, and N content of the seed was similar to grain yield responses. The split N application at planting and the eight‐leaf growth stage was as effective or better than any other treatment for increasing grain yield, N uptake, and seed N content.

ISSN:0190-4167    

DOI:10.1080/01904169109364270

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor