摘要:

Fertilizer trials involving application of phosphorus (P) as both rock phosphate and superphosphate were conducted on adjacent organic and conventional farms in SE-Australia in 1991 and 1992. Seed P concentration and seed P content (P concentration multiplied by seed mass) were higher on the organic farm in 1991 when rainfall was below average, but were higher on the conventional farm in 1992, a wetter year. Addition of superphosphate increased seed P content and concentration on both farms in 1991 and on the organic farm in 1992. These results indicated that seed produced on a conventional farm with addition of fertilizers containing soluble P is likely to have a significantly greater seed P content than seed produced on an organic farm with application of rock phosphate or with no fertilizer addition.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.10823197

出版商:Taylor & Francis    

年代:1998

数据来源: Taylor

摘要:

Exposure to different constant temperatures (12, 17, 22, 27 or 32°C) during the entire life-span of femaleLysiphlebia mirzaivariously affected its longevity, life-table parameters, developmental rate, and mortality of developmental stages of the progeny. The parasitoid develops much faster at 32°C than 12°C. Lower threshold temperature for the development (t1) was 3.02°C and predicted time-to-adult 339.93 degree days. Higher percent mortality occurred at 32°C and 12°C than at 22°C. The adult survived much longer (17 days) at the lower extreme temperature than at the higher one. However, net fecundity (daughters/female) and total fecundity rates (progeny/female) were lowest at 12°C. The female produced the highest number of daughters (163.8) and progeny (242.6) at 22°C. Life-table parameters were temperature dependent; rmwas greater than 0.3 at ≥ 22°C. The results reveal an optimum range of temperatures at whichL. mirzaiperforms well. Most of the life- table parameters vary little between 17 and 27°C, thus, the parasitoid may be adapted for a wide range of temperatures and thus well suited for biocontrol of the cereal aphidRhopalosiphum maidis, in areas where temperatures vary within this range, as in the plains of north India.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.10823198

出版商:Taylor & Francis    

年代:1998

数据来源: Taylor

摘要:

Compared with usual reference values, liquid cattle manure from ecologically-managed farms (n = 13) had low average nutrient contents. In the case of solid manure obtained from cattle (n = 96) and from pigs (n = 18), the proportion of NH4+in the Ntotal(8.4% and 10.3% respectively), the CaO content (0.26% and 0.27% respectively) and, in the case of pig manure, the P2O5content (0.57%), were all relatively low. On the other hand, the K2O content of cattle manure (0.8%) was higher than that quoted in reference values. The manures from deep-litter stables had an above average content of K2O (1.03%). The content of Ntotaldecreased in the sequence deep litter stable > stanchion stable > sloping floor stable. The more frequently the manure heaps were relocated or rotated, and the older they became, the more the content of organic matter and in particular the percentage of K2O in the mineral fraction declined.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.10823199

出版商:Taylor & Francis    

年代:1998

数据来源: Taylor

摘要:

The potential of herbage composts as horticultural substrate and source of nutrients was investigated. The effect of botanical composition of the herbage, as well as the effect of different kinds and amounts of carbon sources, on nitrogen losses during composting and growth properties of the compost were studied. Growth tests with different plant species as well as chemical analyses of total- and easily-soluble plant nutrients were used to evaluate compost quality. Seven herbage composts were studied and used in growth tests with seven different test plants. The results were evaluated by conventional and multivariate statistical methods.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.10823200

出版商:Taylor & Francis    

年代:1998

数据来源: Taylor

摘要:

The purpose of the present studies was to screen for suitable cover crops and seeding rates and investigate the influence of non-suppressed and mechanically suppressed living mulch on white cabbage yield, weed growth, pest damage and green manuring effects. Because no differences in weed suppression between the species/cultivars were found in the first experiment,Trifolium repensL. cv. Pertina, which had least negative impact on cabbage yield was chosen for the second experiment. In addition,Trifolium subterraneumL. cv. Geraldton was included. The competition between cover crop and cabbage was considerable in the second experiment. Mowing once or twice did not improve cabbage yield compared with unmowed treatments. A considerable increase in cabbage yield was achieved both in subclover and white clover by rototilling between the rows 6 weeks after transplanting. The cover crops did not reduce weed biomass or number of weeds early in the season compared with monoculture, but weed biomass in late summer became significantly lower in living mulch. Rototilling was more effective for weed suppression than mowing. Cover crop combined with rototilling reduced weed biomass by 89% compared with untreated monoculture. Subclover living mulch gave the earliest and most ground coverage and the lowest cabbage yield, but it also gave the least insect damage. Both subclover and white clover living mulches gave significantly more marketable cabbage heads than monoculture due to less insect damage. However, damage from caterpillars, primarilyMamestra brassicaeL., was too great in all treatments to produce a commercially viable crop. White clover intercropping in cabbage gave significantly higher oat (Avena sativaL.) yield the subsequent year than monocropping. The implications of the current findings on future efforts to improve intercropping are discussed.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.10823201

出版商:Taylor & Francis    

年代:1998

数据来源: Taylor

摘要:

Biological dairy farming is often advocated as a solution for environmental problems caused by Dutch dairy farming. At the same time, biological farming can improve animal welfare and increase income due to a higher milk price. In this paper the central issue is to quantify economic and environmental consequences for dairy farms when converting to biological dairy farming. A linear programming model is used to model an extensive and an intensive dairy farm typical for the Province of Utrecht, The Netherlands. The objective function of the model maximizes labour income of the farm. From the results it appears that the extensive farm benefits from conversion while the intensive farm loses income. The environmental consequences are quite diverse. The nitrogen surplus after conversion is much lower than before because nitrogen fixation by legumes is omitted from the calculation. On the other hand, ammonia emission is higher after conversion to biological farming due to a higher number of animals. On the extensive farm the phosphate surplus in the biological situation is much higher than in the conventional situation due to the fact that a shortage of nitrogen in the biological situation can only be made up by applying animal manure (slurry) from other farms with consequential overfertilization of phosphate. When environmental legislation is introduced, the biological farms appear to lose more income than the conventional farms. From the sensitivity analysis it appears that assumptions about milk yield per cow and milk price are crucial for the economic results of biological farms.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.10823202

出版商:Taylor & Francis    

年代:1998

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1998.10823203

出版商:Taylor & Francis    

年代:1998

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1998.10823204

出版商:Taylor & Francis    

年代:1998

数据来源: Taylor