摘要:

The interacting effects of combining seedbed harrowing and sowing in darkness, pre-emergence flaming and post-emergence brush weeding for in-row weed control in seeded onions(Allium cepaL.) and kale(Brassica oleraceaeL.var. acephalaDC.subvar. laciniataL.) were studied in field trials in 1994 and 1995. In 1994, only seedbed harrowing and sowing in darkness, and brush weeding significantly reduced weed number and none of the factors studied interacted significantly. The combination of seedbed harrowing and sowing in darkness, and brush weeding reduced weed number by 90% in onions and 84% in kale. Soil cultivation in darkness had no effect on weed numbers in 1995. As in 1994, brush weeding reduced in-row weed number strongly and the combination of flaming and brush weeding reduced weed number in onions by 85%. In kale the combination of seedbed harrowing and sowing in darkness and brush weeding was most effective with a 72% reduction. Contrary to 1994, flaming interacted strongly with crop in 1995, as weed number was significantly reduced in the slow emerging onions but not in the fast emerging kale. Generally, brush weeding did not interact with the other methods, meaning that the pre-emergence methods had neither increased nor decreased the effects of brush weeding. However, in this study the overall effects of combining pre- and postemergence methods have shown promise for obtaining significant reductions in the time required for in-row hand-weeding in row crops grown without herbicides.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755214

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The use ofMucuna pruriensas source of N for the succeeding poor N-fixing soyabean genotypes was tested during the 1991/92 rainy season at the IDR site. Field studies revealed thatM. pruriensproduced 31 nodules plant−1with a nodule mass of 306 mg plant−1and a crop N yield of 340 kg ha−1. This high nodulation was attributed to a wide range of indigenous rhizobia identified as strains ofBradyrhizobiaisolated from nodules ofStylosanthes gracilis(two isolates G7, G71),Crotalaria juncea(two isolates C4, C41),M. pruriens(two isolates II, 13),Mimosa pudica(three isolates W3, W31, W32) andPhaseolus vulgaris(one isolate H51), which formed nodules with dark red interiors onM. pruriensas revealed by the plant-infection test. The antibiotic resistance profile differed among the various isolates, and among isolates of the same plant of origin. Consequently, the use ofMucunaas green manure for the succeeding soyabean crops is quantified as a fertilizer-N equivalent of as much as 95 and 80 kg N ha−1for genotypes cv. FN3 and cv. IRAT 274 respectively. Our findings illustrate the high agronomic efficiency ofM. pruriensfor soyabean.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755215

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Interrelationships between the three trophic levels; resistant and susceptible corn,Zea mays, a cereal aphid,Melanaphis sacchari(Zehntner), and a braconid aphid parasitoidLysiphlebus delhiensis(Subba Rao & Sharma), were studied in the laboratory and the interaction between plant resistance and the efficiency of the parasitoid was evaluated. For the assessment of parasitoid efficiency, its age-specific life tables were constructed at different host density levels. Greater survival, progeny production, female progeny and intrinsic rate of natural increase of the parasitoid were observed on the resistant cultivar than on the susceptible one. The results suggest that the reproductive success of the parasitoid was better on the corn cultivar resistant to the aphid M.sacchari, implying a synergistic effect of plant resistance on biocontrol of the aphid. Therefore, there should be no reason why plant resistance and biocontrol cannot be a highly effective and compatible combination within an IPM for aphids.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755216

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Systems theory differs from classic analytical science by producing statements in the context of a descriptive system rather than seeking to reduce a complex problematic situation to researchable entities. This paper analyzes the validity and applicability of systems theory as a scientific approach towards organic farming. The world-views on which organic farming and systems theory build, respectively, are discussed and the methodological consequences of these world views are clarified. The world-view inherent in organic farming, the ontological level, as reflected in stewardship towards nature, the ethic of animal husbandry, and the cycling processes in nature, is harmonious with the underlying ideas of systems theory as regards a hierarchical structure and a mainly anthropocentric stand. This world-view is not paradigmatically different from the world-view inherent in conventional agriculture but non-consistent with the world-view of deep ecology. The world-view of organic farming acknowledges the wholeness in every system with emerging phenomena we might not perceive on an epistemological level. This world-view also acknowledges that such emerging phenomena occur at the higher levels of the hierarchical structure, which is in accordance with systems theory. Originally, a system was defined by its relations to its environment. However, in order to avoid the potential reductionism that may arise when everything is reduced to the ultimate whole system, it is found necessary also to identify and describe the major mechanisms within each system. It is concluded that meeting this requirement, systems theory can be viewed as an extension of traditional methods as the problems become more complex at higher hierarchical levels. Unfortunately, biologically speaking, we still have a limited knowledge of these mechanisms or processes in organic farming, but one of the challenges of today's science in organic farming is to identify and define these mechanisms on every hierarchical level.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755217

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Organic vegetable transplants are produced in Israel in ‘Speedling’ trays. The commercial growth medium consists of a mixture of peat moss and vermiculite (PV). Commercially grown transplants frequently exhibit non-uniform quality. Growers experience unacceptable mortality rates during the first weeks after transplanting. Substituting part of the peat moss with compost, based on the coarse fraction of cattle manure (CPV), caused a significant improvement of the growth rate of the seedlings in the nursery. Improved parameters included fresh and dry weight of the seedlings. Possible reasons for improved growth are discussed. After transplanting to the field, CPV-grown cabbage transplants exhibited lower mortality rates caused byPythium ciphcinidermatumthan PV- transplants. The yield of CPV-transplants at harvest weighed more than that of the PV-transplants although non-infested control plants yielded similarly to those grown in compost-containing media. The effect on processing tomato transplants was different. Although all plants survived, the superiority of the CPV-transplants manifested itself at harvest in terms of higher yields. Compost suppressed infestation of sweet basil plants by inoculum ofFusarium oxisporumf.basilici.Under identical condition,Fusariumcaused severe growth inhibition and even death of peat-grown plants.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755218

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of inoculation by arbuscular mycorrhizal fungi (AMF) and indigenous AMF populations on biomass production and phosphorus (P) uptake by leek and on its utilization of P in Kola apatite and bone meal was studied in field soils. Arbuscular mycorrhiza (AM) did not enhance P uptake from Kola apatite, which had no clear effect on P uptake by leek within one growing season, either in the field or in pots. AM increased P uptake from bone meal by 62% in a pot experiment. Inoculation did not increase the effect in unsterile soil as compared with the indigenous AMF populations. The results demonstrate a key role for AM in utilization of organic P.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755219

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An experiment was conducted to assess the N availability of roots of woody species and maize. The trial was conducted using a split-plot design with four replications. Four incubation periods (0, 2, 4 and 6 months) made up the main plots. There were six subplots, consisting of addition of fine roots (< 2 mm diameter) of four woody species(Dactylcidenici barteri, Senna siamea, Gliricidia sepiumandLeucaena leucocephala) and maize(Zea mays), and a control with no roots added. Roots from four-month-old plants were used in this study. Maize as test plant was grown in pots containing sandy loam soil (Psammentic ustorthent). Incubation period of roots before planting maize increased maize dry matter yield and N uptake. Addition ofGliricidiaandLeucaenaroots which have high? content and low C/N ratio (13.1 and 14.0 respectively) improved maize dry matter yield and N uptake following 2 months incubation. Application of maize roots which have low N content and high C/N ratio (40.3) reduced maize dry matter yield and N uptake. Application ofDactyladeniaandSennaroots had an intermediate effect on maize dry matter yield and N uptake. Maize dry matter yield and N uptake were significantly and inversely correlated with the C/N ratio of the added roots with 0, 2, and 6 months incubation. No relationships were observed between the other root chemical characteristics and maize dry matter yield, and N uptake.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755220

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755221

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755222

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755223

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor