摘要:

Data are presented on the nutrient balance at the farm gate of a 52.4 ha mixed farm in Southern Germany which, since 1929, has produced increasing yields under marginal site conditions and buying in plant nutrients only in the form of some feedstuffs and straw. The farm has complete records which cover the period 1952–1981. The external input of nutrients was 29.6% N, 30.8% P and 125% K (K mainly from straw) of the amounts sold in the produce. The nutrient balance since 1952 at the farm gate has been −14.1 kg N, −2.19 kg P, +1.04 kg K per hectare per year. The nitrogen sold in plant products was 51.1% from 1951 until 1970, and 32.0% from 1971 until 1981, of the total sales in animal and plant products. Soil tests for available nutrients show minor differences from 1972 until 1982 of phosphorus, potassium and magnesium. However, a higher input of feedstuffs since 1970, which was needed to finish breeding bulls from the farm's own herd, resulted in a considerable increase during these ten years of soil organic matter and nitrogen in the soils under permanent plant cover. The annual accumulation of nitrogen amounts to 1446 kg N for the whole farm. During the same period the C:N ratio of soil organic matter in all fields has increased from 8.3 to 9.6. This is interpreted as an accumulation of organic matter with a shorter half life. It is argued that the local climate is the limiting factor that slows down the nitrogen mobilization from the soil resource leading to this accumulation. By taking account of the site conditions, manure handling and application, an estimate is made of the annual losses and gains of N, P and K for the farm. The figures arrived at suggest that the farm approximates sustainability.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754508

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Sixty specimens of Ichneumonidae (Hymenoptera), representing 20 species and 4 subfamilies, fed at the extrafloral nectaries of faba bean (Vicia fabaL., cv ‘Ipro’, Fabaceae) grown in replicated plots. Of those attacking lepidopterous pests, 3 species were known parasites of agricultural pests, 2 of forest insects, and 3 of both agricultural and forest pests. Eleven species had no recorded hosts. Faba bean seeded July 31st attracted large numbers of Ichneumonidae from mid-September through mid-November, may have provided food for overwintering adults of several of the species involved. Testing should continue on faba bean grown in conjunction with orchard, vegetable, and forest crops, because it can enhance soil fertility, and may help to sustain parasites of lepidopterous pests.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754509

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The purpose of the study was to monitor the trend of N build-up in wood shavings used as bedding for sheep/goats fed on leguminous fodder supplementation and to determine effects of increasing levels of supplementation in the diet on manurial value of the litter. Basal diet consisting ofad libitumguinea grass (Panicum maximum) was supplemented with leguminous fodder at four levels: 200, 400, 800, 1200 g DM/head/day. Samples of wood shavings mixed with faeces, urine and spilled feed were taken at 2-week intervals after penning the animals for a period of 7 weeks and then analysed for N content. Manure from the four feed types was compared at three rates of application (4, 8, 12g/kg soil) in a pot trial. A second trial was run to test effects of increasing levels of wood shavings on immobilization of applied and native N. Generally, accumulation of N in litter increased progressively with time. Increasing leguminous fodder supplementation in the diet improved manurial value of bedding. Wood shavings used as bedding appeared to decrease agronomic value of manure.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754510

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In an experimental grove of pecan (Carya illinoinensis[Wangenheim] K. Koch [Juglandaceae]), we surveyed potential “insectary crops” that might provide aphidophagous insects and other entomophaga with alternate foods, and thereby enhance biological pest control. Thirteen prospective warm-season cover crops were evaluated for associated aphids and entomophagous insects; an additional 11 crops or mixtures were considered in unreplicated plots. Seven crops developed adequate stands in the replicated study: sericea lespedeza (Lespedeza cuneate[Dumont] G. Don, cultivar ‘Lowtan’, Fabaceae), American jointvetch (Aeschynomene americanaL., Fabaceae), sesbania (Sesbania exaltata[Rafinesque-Schmaltz] Cory, Fabaceae), cowpea (Vigna unguiculatassp.unguiculata[L.] Walpers, no named cultivar, but termed “combine” or “reseeding” cowpea, Fabaceae), alyceclover (Alysicarpus vaginalis[L.] De Candolle, Fabaceae), a sorghum X Sudan grass hybrid (Sorghum bicolor[L.] Moench cultivar ‘Kow Kandy’, Poaceae), and buckwheat (Fagopyrum esculentumMoench, Polygonaceae). Together with late-seeded sunflower (Helianthus annuusL., cultivar ‘Triumph 565’), these were assessed weekly for crop- plant density, vegetational cover, and height; vegetational cover by weeds; and densities of insects. All crops except sorghum showed substantial declines in density through time, due to drought, pathogens, nematodes, shade, or a combination of these factors. Sesbania and buckwheat were the only crops that exhibited substantial declines in vegetational cover, whereas alyceclover showed a substantive increase. Sorghum attained the greatest mean height, followed by sesbania, alyceclover, sunflower, American jointvetch, cowpea, buckwheat, and lespedeza.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754511

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The present work was undertaken to evaluate the effect of three cucurbit host plants,viz., Lagenaria vulgaris, Luffa cylindricaandCucurbita maximaon the oviposition pattern, fecundity, developmental rate, longevity and sex ratio of the parasitoidTrioxys indicuson its hostAphis gossypii.The daily oviposition pattern ofT. indicusdid not vary significantly in host insects bred on different host plants. However, the frequency of oviposition was significantly less in the hosts bred onC. maximathan others. The female laid about 80% of the total eggs during the first four days irrespective of the host plants. The females oviposited for 8.3 ± 0.95 days, 5.5 ± 1.08 days and 5.3 ± 0.67 days in the hosts reared onL. vulgaris, C. maximaandL. cylindricarespectively. The oviposition period also corresponded with the life-span. Host plants significantly influenced the mean fecundity ofT. indicus.It was approximately three times as high on the aphids bred onL. vulgaris(164.5 ± 18.87 mummies/female) andL. cylindrica(144.0± 18.16mummies/female)than onC. maxima(51.3 ± 13.57 mummies/female). The rate of development of both sexes ofT. indicuswas not influenced by host plants at all. However, host plants significantly influenced the sex ratio of the parasitoid;C. maximasubstantially reducing the production of females. The findings established a direct relationship between the host plants and the parasitoids and, therefore, the importance of the host plants as a factor in the success of a bioagent should also be considered.

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754512

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754513

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754514

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754515

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754516

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1989.9754507

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor