摘要:

Carob seedlings were grown at different proportions of nitrate NO3) and ammonium (NH4) supplied at a concentration of 3.5 mM nitrogen (N). The effect of five different combinations of NH4‐ and NO3‐N on growth rates, N and carbon (C) content of the plant and dry matter distribution were studied. The presence of NH4in the nutrient solution enhanced plant growth rate, although net photosynthesis rates per unit area were lower than in NO3‐fed plants. Nitrate‐fed plants exhibited the highest rates of carbon dioxide (CO2) assimilation, water use, and N‐use efficiency. Nevertheless, plants growing only with NO3were more fragile and susceptible to fungus infections. The role of cotyledons on the regulation of the supply of photosynthates from leaves to roots in the different combinations of NO3and NH4is described. Results suggest that the growth rates of carob may be improved using suitable combinations of NO3‐ and NH4‐N. Equal concentrations of these two N sources allows good development and adequate allocation of low C and N to different developing sinks of the carob seedlings.

ISSN:0190-4167    

DOI:10.1080/01904169309364511

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Alfalfa or lucerne(Medicago sativaL.) is an important forage legume grown extensively in the world. There have been relatively few investigations on the adaptation of alfalfa to soils found in suitable eco‐zones in Africa. In the present investigations, twenty accessions were evaluated for tolerance to soil acidity, low phosphorus (P) and tolerance to aluminum (Al), and their response to P in nutrient solutions to identify indicator cultivare for acid soil mineral stresses.

ISSN:0190-4167    

DOI:10.1080/01904169309364512

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Although lablab(Lablab purpureusL.) is grown in many parts of Africa relatively little investigation has been done on its adaptation to acid soils, which are generally low in available P. In the present study, lablab was evaluated for tolerance to acidity and low available P on two Ethiopian soils. The two soils were a Nitosol (Soddo soil) and a clay loam with 77% Al saturation (Chencha soil). The pH of the Soddo soil unlimed was 4.8 and 5.6 when limed and with 0 and 37.5 mg P/kg soil applied at each lime rate. The treatments on the Chencha soil were pH 4.1 and 5.9 with combinations 0 and 25 mg P/kg added.

ISSN:0190-4167    

DOI:10.1080/01904169309364513

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Sesbania, particularlyEsnabia sesbanspecies, grow naturally in many parts of Africa where they form natural browse. Productivity of Sesbania as animal feed is widely limited by soil acidity and low P. In this study, eighteen ILCA accessions ofS. sesbanand two ofS.goetzei, all but two from Africa, were evaluated for tolerance to acidity and low P on two Ethiopian soils as well as their tolerance to Al and response to P in nutrient solutions. The treatments were 0 and 4000 mg CaCO3/kg (pH 4.8 and 5.6) in combination with 0 and 37.5 mg P/kg on a Soddo Nitosol. On the Chencha clay loam with 77% Al saturation, the pH values were 4.1 (unlimed) and 5.9 (limed) in combination with 0 and 25 mg P/kg on the unlimed soil plus 37.5 mg P/kg on the limed soil. Treatments applied to the nutrient solutions were 0, 3, and 6 ppm (0, 111, and 222 μM) Al in combination with 5 and 200 μM (155 and 6200 ppm) P as KH2PO4.

ISSN:0190-4167    

DOI:10.1080/01904169309364514

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Esbania have multifarious utilization, and in many instances growth rate is one of the most important criteria for the selection of suitable esbania. This paper reports results of a study on the growth rates of esbania on two acid soils both low in available P, but one with toxic levels of Al. Growth rate was assessed by measuring plant height at 21, 29, 35, 45, 52, and 60 days on a Nitosol (Soddo soil), and at 52 and 60 days on a clay loam (Chencha soil). Growth was also evaluated in nutrient solutions containing 0, 3, and 6 ppm Al in combination with 155 and 6200 ppm P.

ISSN:0190-4167    

DOI:10.1080/01904169309364515

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Seven cultivars and strains of winter oilseed rape(Brassica napusL.) were tested for tolerance to drought and soil acidity and for response to nitrogen fertilization. Plants were grown in ceramic cylinders (with no bottoms) buried to ground level at a field site in Poland. Cylinders contained a gray brown podzolic soil having a medium sandy texture and variable pH due to history of fertilization. Periodic drought (from early budding to late flowering) was imposed by covering the field plots with polythene film. Rainfall excluded by the film was compensated by watering the non‐stressed plants. Based on seed yields, rape cultivars and strains differed significantly in tolerance to drought. ‘Jet Neuf’ was most tolerant and ‘Bolko’ least tolerant. Cultivars also differed significantly in response to N fertilization, with Bolko being the most responsive cultivar tested. Rapeseed yields were generally reduced by 20% at a soil pH of 4.2, compared with pH 6.2 (determined in 1M KC1), but cultivars did not differ significantly in acid soil tolerance. Specific yield‐limiting factors in the acid soil were not identified, but a mild A1 toxicity was suspected. A higher level of acid soil (A1) toxicity will be needed to study A1 × drought × rape genotype interactions. Reductions in soil moisture or pH levels did not significantly affect the fat and protein contents of rapeseed. Variations in fat and protein contents observed were due largely to cultivar differences. Jet Neuf tended to have the highest protein and the lowest fat content. ‘Jantar’ was the highest in fat content and one of the lowest in protein content.

ISSN:0190-4167    

DOI:10.1080/01904169309364516

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Aluminum (Al) tolerant sorghum(Sorghum bicolorL. Moench) genotypes are needed for use on strongly acidic, infertile soils of the tropics and subtropics, where the crop is often grown in a low input, subsistence type of agriculture. Eleven genotypes were first screened for Al tolerance in greenhouse pots of acid, Al‐toxic Tatum subsoil (clayey, mixed, thermic, Typic Hapludult) at pH 4.3 and 5.3. In two subseguent experiments, four genotypes showing wide differences in acid soil tolerance in the first test were grown over pH ranges of 4.3 to 6.4 and 4.7 to 7.0. Acid soil tolerance was determined by absolute dry shoot and root weights at low pH and relative (low pH/high pH%)shoot and root weights. Genotypes differed by as much as 10 fold in relative shoot weight and 8 fold in relative root weight. Genotypic tolerances to acid, Al toxic Tatum subsoil were in good agreement with those obtained on acid field sites in Georgia and Brazil. Hence, results indicated that Al toxicity is a major selection pressure factor in sorghum breeding programs of both regions. SC283 and SC574, originating in Tanzania and Pakistan, respectively, were most tolerant to the acid Tatum subsoil. RTx430 and RTAM42S, both from Texas, were among the least tolerant. Other sensitive genotypes included RTx2536, SC214, SC170, SC369, and SC599. A tissue culture derivative of the acid soil sensitive RTx430 genotype [RTx430 (TC)], showing tolerance to drought/salinity in Arizona and acid soil in Georgia, ‘ was significantly more tolerant to the acid soil than the RTx430 parent. The acid soil tolerance of this genotype also exceeded that of SC574 and approached that of the most tolerant genotype SC283.

ISSN:0190-4167    

DOI:10.1080/01904169309364517

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

During the third year of a long‐term carbon dioxide (CO2) enrichment study, macro‐ and micro‐nutrient concentrations in leaves and roots of sour orange trees were analyzed. Data for yearly courses of the macronutrients Ca, Mg, N, P, K, Na, and S and the micronutrients B, Cu, Fe, Mn, and Zn are presented. Significantly higher concentrations of N, K, Ca, and Mn were found in leaves of the control trees. The degree of difference varied seasonally: the greatest differences occured in summer, whereas essentially no differences were found in spring and winter.

ISSN:0190-4167    

DOI:10.1080/01904169309364518

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Symbiotic nitrogen fixation is an essential ecological attribute for sustained amelioration of severely eroded, low fertility soils. The long‐lived perennial,Sericea (Lespedeza cuneata(Dument) G. Don.), is highly tolerant of depleted soil conditions and has exceptional nitrogen fixation capabilities. Objectives of this study were to determine nodulation characteristics, with adjunctive governing factors, that influence 20 year‐age Sericea growth, effectual nitrogen fixation and subsequent improved soil productivity of eroded Dougherty loam (Loamy, mixed, thermic, Arenic Haplustalf). A first‐year lime application resulted in significant favorable Sericea growth and nitrogen fixation throughout the 20‐year period. Sericea growth and nodulation declined approximately one‐third during the second decade of plant age. However, annual nodule regeneration remained at nearly the same level. Peak nitrogenase activity levels occurred with favorable mycorrhizal colonization. Distinctive nonmature and mature nodule morphology contributed to well defined histology for cellular cytology that is associated with ureide transformations unique for Sericea nodule enzyme compartmentation. Soil organic matter increased from 0.35% to 2.65% during the 20‐year Sericea growth.

ISSN:0190-4167    

DOI:10.1080/01904169309364519

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Two experiments were conducted to determine if malate and citrate change diurnally, if these changes are light dependent, and how these changes relate to K+and NO3−1levels. Malate concentration in tomato leaves was shown to increase during the day and decrease at night. The inverse occurred with citrate. The dependency of the changes on light was demonstrated for malate, but not for citrate. A relationship with NO3−assimilation and K+recirculation may explain the changes in malate concentration.

ISSN:0190-4167    

DOI:10.1080/01904169309364520

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor