摘要:

Twenty-seven popular South African inbred maize lines, four commercial maize cultivars, two sweet corn cultivars and two grain sorghum cultivars were screened by means of a rapid, semi-quantitative method to determine DIMBOA concentration. Significant differences were found between inbred lines. Sweet corn cultivars exhibited a relatively high concentration of DIMBOA, while grain sorghum contained a very low concentration. Although differences in concentration between plants cultivated from different seed sizes were found, no definite trend could be established.S. Air. J. Plant Soil1984, 1: 99–102

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634120

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor

摘要:

The growth response of five inbred maize lines with high and low DIMBOA content were compared in the presence of 3 and 12 ppm atrazine. A growth-promoting effect of atrazine on roots, mesocotyls and coleoptiles was observed in dark-grown seedlings of the low DIMBOA concentration lines, whereas virtually no effect could be detected in high DIMBOA concentration lines.S.Afr. J. Plant Soil1984, 1: 103–105

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634121

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor

摘要:

Physiological leaf abnormalities and boll yield of cotton (Gossypium hirsutumL.) as affected by potassium, calcium and boron nutrition.A pot trial with a sand medium and two levels each of K, Ca and B nutrition, factorially arranged, was carried out with cotton over a period of 13 weeks. A low level of B nutrition resulted in stunted plants. The high K level suppressed Ca uptake, resulting in a K X Ca interaction. A low boll yield and distorted leaves in the growing point were associated with deficient Ca nutrition. A high K level had a detrimental effect only at the low Ca level. Necrotic lesions, that may be confused with infection byXanthomonas malvacearum(E.F. Smith) Dowson, occurred on leaves at the low Ca and B levels. Damage to cell walls in the spongy parenchyma or to phloem cells of the leaf veins preceded the development of necrotic lesions. Transparent spots were the result of a group of enlarged cells containing almost no chloroplasts, which developed between the two epidermal layers.S.Afr. J. Plant Soil1984, 1: 106–110

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634122

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor

摘要:

The effect of mulching and irrigation frequency on tuber yield was investigated during three seasons at the Glen Agricultural Research Institute The soil on the experimental site consisted of a loamy sand topsoil and sandy clay subsoil with 94 mm total available water in the top 775 mm of the soil profile. A wheal straw mulch of 14 t ha−1reduced soil temperature and increased tuber yield consistently (averaged over all irrigation treatments in all three seasons, mulched plots produced 30% more tubers than bare plots). Tuber yield also responded well to increased irrigation frequencies it was concluded that the cooling effect ot frequent irrigation could be obtained much cheaper by mulching It is recommended that from commencement of stolonization, potatoes should be irrigated with 50 mm of water as soon as 50 mm of water has evaporated from a Class A pan for an unmulched crop and 65 mm for a mulched crop.S Afr J. Plant Soil1984. 1: 111–116

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634123

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor

摘要:

The irrigation scheduling model IRRISCHED-4, here described, enables the irrigator to choose one of four techniques for estimating crop water use, depending upon data available. Daily inputs include maximum and minimum temperatures, sunshine hours, leaf area index, crop factor, rain, and irrigation. The model is run on a programmable pocket calculator. The techniques used in determining daily soil-water status depend on Class A pan evaporation, the Linacre and Blaney&Criddle equations, and a modified version of the Priestley&Taylor equation. These four techniques were tested over two seasons at Cedara and compared to lysimeter-determined values of evapotranspiration. All methods perform satisfactorily but the modified Priestley&Taylor method provided the most reliable evapotranspiration estimates, owing to the utilization of leaf area index data.S. Afr. J. Plant. Soil1984, 1: 117–121

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634124

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor

摘要:

In a field trial with maize, applications of potassium (K) proved to have a highly significant effect on stalk strength, premature death, root lodging and stalk breakage. A week prior to harvest the percentage of lodged plants varied from 77% in plots which received 50 kg K ha−1to 47% in plots which received 200 kg K ha−1. Although some stalk breakage of green plants and root lodging were evident, premature death was clearly the prime cause of lodging. Significantly, premature death and stalk breakage were lowest in plots which received no K fertilization. The virtual absence of ears precluded the establishment of the carbohydrate sink, considered to play an important role in predisposing plants to invasion by stalk-rot organisms. The marked effects of K observed in this study suggest that K stress could profitably be used as a selection aid in breeding programmes. It seems probable that discrimination in terms of standability will be reduced when crops are adequately fertilized with K.S. Afr. J. Plant Soil1984, 1: 122–124

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634125

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor

摘要:

Veldkapasiteit (VK) is bepaal op 5x5 m-persele op verskeie gronde in Wes-Kaapland. Tekstureel het die gronde gewissel van growwe sand tot sandklei. Gronde van die Avalon-, Dundee-, Fernwood-, Hutton-, Oakleafen Westleighvorme is gebruik. Matrikspotensiaal (ψm) is gemonitor met kwiktensiometers, terwyl waterinhoud gravimetries bepaal is. Veldkapasiteit is op vyf gronddieptes bepaal en het gewissel van 4,9% tot 27,2% op massabasis. In totaal is 105 bepalings op 23 persele uitgevoer. Lineêre korrelasiestudies het getoon dat daar 'n swak verwantskap bestaan tussen % klei (r= 0,40), % slik + klei (r= 0,53), % fynsand (r=−0,52) en hidrouliese geleivermoë(K) (r=−0,42), onderskeidelik, en matrikspotensiaal by VK. Hierdie tekstuureienskappe en K is nog swakker gekorreleer met die tydsverloop vanaf versadiging tot VK. Trosontledings het alle waarnemings in 'n aantal goed afgebakende groepe geplaas op basis van die genoemde deeltjiegroottefraksies en grond- watereienskappe. Vyf tekstuurgroepe is geïdentifiseer. Die ontledings het getoon dat (i) daar geen uniekheid is in die groeperings sover dit lokaliteite of grondvorme betref nie; (ii) matrikspotensiaal by VK 'n funksie van hidrouliese geleivermoëis; (iii) daar gevolgllk nie 'n unieke verband bestaan tussen tekstuur enψby VK nie; en (iv) daar geen verwantskap bestaan tussen tekstuur of hidrouliese geleivermoë, en die tydsverloop vanaf versadiging tot VK nie.S.-Afr. Tydskr. Plant Grond1984, 1: 125–131

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634126

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor

摘要:

Three levels of nitrogenous fertilizer were applied to oriental tobacco (Nicotiana tabacumL. cv. Elcatra) at different spacings and topped to 14 and 28 leaves per plant respectively. Yield, income, total nitrogen and total alkaloids of the cured leaves increased, and total reducing sugars decreased as nitrogen application was increased. Acceptable levels of quality attributes such as total nitrogen, alkaloids, and reducing sugars, as well as a high income, were obtained when plants were spaced 20 cm from each other in 25 cm twin rows with an interrow space of 50 cm, topped to 28 leaves and fertilized with a high level of N (72 kg N ha−1).S. Afr. J. Plant Soil1984, 1: 132–134

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634127

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor

摘要:

Thirteen herbicides were tested for toxicity against strains ofRhizobiumused in South African legume inoculants for lucerne, clover, soybeans, groundnuts and lupins, respectively. Each of alachlor, bromoxynil, proprop, metolachlor, naptalam + dinoseb, and trifluralin inhibited at least two of the strains after a contact period ofca10 s.Nostrain survived 42 h in contact with any of these herbicides. Atrazine and terbutryn were relatively non-toxic. The slow-growing strains ofRhizobium japonicum, Rhizobium lupiniandRhizobiumsp. (groundnuts) were less affected by at least two of the herbicides tested than strains of the fast-growingR. melilotiandR. trifolii.Toxicity of a herbicide to rhizobiain vitrodid not necessarily correlate with its effect on nodulation and some are considered suitable for field application.S.Afr. J. Plant Soil1984, 1: 135–138

ISSN:0257-1862    

DOI:10.1080/02571862.1984.10634128

出版商:Taylor&Francis Group    

年代:1984

数据来源: Taylor