ISSN:0190-4167    

DOI:10.1080/01904169009364146

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Literature review indicates that higher crop yields may be obtained with a mixture of nitrate and ammonium than with either source alone. An adequate supply of potassium enhances ammonium utilization and thus improves yields, when a mixed ammonium‐nitrate nitrogen nutrition is applied.

ISSN:0190-4167    

DOI:10.1080/01904169009364147

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In a greenhouse experiment with wheat, sandy loam or clay soils were salinized by additions of 0, 3. or 8 g NaCl/3L pot. Ammonium and nitrate nitrogen mixtures in ratiosof0/100, 25/75 and 50/50 together with DCD, a nitrification inhibitor, were applied with irrigation water.

ISSN:0190-4167    

DOI:10.1080/01904169009364148

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The objective of this study was to evaluate the effect of the NO3‐/NH4+ ratio in the nutrient solution, combined with seasonal ambient temperature and irradiation level provided toPelargonium zonalecvs. ‘Empress’ and ‘Rubin’ stock plants, on production and their cuttings’ qualities. Plants were grown for 7 months on tuff:peat medium with three NO3‐/NH4+ ratios, in a greenhouse with high natural irradiance conditions or at reduced irradiance level (30% shading simulated the marginal production season). Cutting production was negatively affected by the low irradiance level and low ambient temperature. The NO3‐/NH4+ ratio did not affect cutting yields in natural and reduced irradiance except for a very high NH4+ proportion (70%) in the solution. Rooting ability and quality were affected reciprocally by the irradiance level, compared with yield. The NO3‐/NH4+ ratio applied in the two irradiance regimes affected the rooting significantly; a low ratio was preferable at low irradiance level and low temperature. Carbohydrate content could serve to predict the propagation capability of the cuttings.

ISSN:0190-4167    

DOI:10.1080/01904169009364149

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The response of melon plants (Cucumis meloL. cv Galia) to different ratios of NH4‐N/(NH4+NO3)‐N (0, 0.15, 0.3 and 0.6) in saline (9 dS/m) and nonsaline (1.5 ds/m) nutrient solutions (in which the total N level was 5 mmol l‐1) was studied using an aerohydroponic system in a greenhouse. The total production of dry matter and the concentration of macronutrients and other elements in plant shoot and root tissue were determined 68 days after transplanting. Dry matter production was not significantly affected by the NH4/N03ratio but the following general trend of NH4. effect on crop yield cannot be ignored. In nonsaline solutions the presence of a relatively low proportion (0.15) of NH4‐N enhanced the yield of shoot dry matter, whereas under saline conditions the presence of NH4exerted a negative effect on plant growth. Ammonium nutrition tended to increase the level of total N in plant tissue. Increasing NH4/NO3ratio (decreasing NO3level) resulted in higher Na and Cl and lower Ca, K and NO3levels in plant tissue. The concentration of Mg in plant tissue was the result of the interactions between the NH4/NO3ratio and salt effects.

ISSN:0190-4167    

DOI:10.1080/01904169009364150

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Various physiological effects of ammonium, nitrate and mixed ammonium‐nitrate nutrition of plants have been studied in this laboratory during the last years. Some of the characteristic distinctions observed between plants growing on these nitrogen sources are described and discussed. Biomass production of ammonium‐grown plants increased with K+concentration in the nutrient medium between 0.1 to 3 mM , while nitrate‐fed plants reached maximal growth around 0.25 mM K+. The water use efficiency (WUE) of ammonium‐fed plants was lower and also more dependent on K+than that of plants receiving nitrate. At low K+levels (0.1 mM) in the medium, plants growing on ammonium‐N spent nearly twice as much water through transpiration per unit mass than nitrate‐fed plants. WUE of plants receiving NH4NO3was poor at low K+(similar to ammonium‐fed plants) but at high K+this plants grew even better than nitrate‐grown plants. Overall transpiration per plant was little affected by K+levels in the medium. Consequently, the main effect of K+was on the overall photosynthetic capacity of the shoot.

ISSN:0190-4167    

DOI:10.1080/01904169009364151

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The effect of ammonium ion in the solution on plant growth and ionic composition is reviewed.lt is demonstrated that ammonium is taken up in preference to nitrate when its concentration is above 10 % of total nitrogen in the nutrient solution. Ammonium is a safe source at low root temperatures, and is dangerous at high temperatures. Sensitivity of crops to ammonium varies between species. Chinese cabbage may die in the presence of 5 mM ammonium but thrives on 0.05 mM. The response of various crops to various ratios of ammonium in the solution leads to the conclusion that the rate of sugar supply to the roots minus the demand for root respiration is the key factor that controls the ability of the plant to assimilate ammonium in the root.

ISSN:0190-4167    

DOI:10.1080/01904169009364152

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The objective of this study was to determine the distribution of Se in rainfall in two sites in the arid regions of western Colorado that also supported accumulator species of the genus Astragalus (milk vetch). In addition it was of interest to discover the selenium (Se) cycle in members of this genus. To elucidate the Se cycle in these perennials, samples of plants and soils were collected throughout several growing seasons. Se was not detected (< 2ug/L) in any of 12 rainstorms sampled. Nor was any Se found in rain falling through nonaccumulator plants. All the Se detected in rain falling through accumulators was water soluble and most of the Se in leaves of these plants was also water soluble (90–92%). Accumulator plants underwent a progressive loss of Se throughout the growing season beyond the full bloom stage. Prior to the initiation of the following year's growing season, the Se content of accumulator plants was <5 ug Se/g. During years of adequate rainfall the soils beneath the accumulator plants increased in Se content reaching a peak in the early spring. Soils beneath nonaccumulator plants varied little in their total Se content during the growing season.

ISSN:0190-4167    

DOI:10.1080/01904169009364153

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Two fertilizer studies were conducted on mature vineyards established with a water harvesting system on a White House sandy loam (fine, mixed, thermic, Ustollic Haplargid) soil at the University of Arizona Oracle Agricultural Center. In one study, two grape (Vitis viniferaL.) cultivars, ‘Cabernet Sauvignon’ and ‘Sauvignon blanc’, were treated with different levels of15N and P fertilizer and tested for tissue NO3‐N and total‐P content. In second study, eleven grape varieties were treated with three levels of N. Tissue samples were analysed for total P and NO3‐N content, and the ratio of petiole‐P to leaf blade‐P was determined. When sufficient quantities of both nutrients were provided, N and P interacted positively resulting in increased grape yields. The petiole‐P to leaf blade‐P ratio correctly monitored the P status of the vines.

ISSN:0190-4167    

DOI:10.1080/01904169009364154

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Urea was spray‐applied to a Kentucky bluegrass(Poa pratensisL) turf at a rate of 50 kg N ha‐1. Two volumes of solution were used to provide application depths of 0.5 and 2.0 mm. Ammonia volatilization and the rate of disappearance of the applied N were then examined over a 48 hr period. Urea‐N was positioned primarily on shoots with the 0.5 mm application, whereas the 2.0 mm application distributed the urea equally between the shoot and the thatch/soil layers. Urea positioned in the thatch/soil was hydro‐lyzed rapidly, while very little hydrolysis occurred with the urea positioned on the shoots. Cumulative volatile loss amounted to 5.3% and 11.6% of the applied N with the 0.5 and 2.0 mm application, respectively. Applied urea‐N disappeared rapidly from the turf/soil system. Approximately 80% and 100% of the applied N was depleted by 48 hr for the 0.5 and 2.0 mm application, respectively. The duration of volatile loss was correlated with the period that the urea‐N was resident in the turf profile.

ISSN:0190-4167    

DOI:10.1080/01904169009364155

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor