摘要:

Lettuce, favabean and pea were grown as sole crops and as intercrops in all 3 paired combinations (ie. fava:lettuce, pea:lettuce, fava:pea) with 4 different row arrangements (ie. 1:1, 1:2, 2:1, 2:2) under weeded and unweeded conditions. The weed biomass and diversity, as measured by species richness, were recorded for all unweeded treatments. The crop yields and land equivalent ratios (LERs) were determined for all treatments. Weed biomass was significantly reduced compared to sole crops by intercrops of fava:lettuce in 1:1 and 2:2 row arrangements, by fava:pea in 1:1,1:2 and 2:1 row arrangements, but not by pea:lettuce in any row arrangement. Weed diversity was not significantly different compared to sole crops for all intercrop treatments. Yield reductions by weeds in the intercrops ranged from 23 to 40% for lettuce, from 19 to 42% for fava, and from 15 to 50% for pea. Yield reductions by weeds were dependent on crop combination and row arrangement, not necessarily weed biomass, and suggested treatment differences on critical times for weed interference. LERs for all intercrop treatments were greater than 1.0, except for the weeded 2fava:21ettuce, 2pea:llettuce and lfava:1pea plots, and were always greater under unweeded conditions.

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754615

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Case studies examining nitrogen supply dynamics were carried out on two biodynamic farms in Sörmland (for a 7 year rotation period on one farm and 3 years on the other) and on one biodynamic farm in Skåne (for 3 years) in Sweden. Each of the farm locations had a different set of climatic and soil conditions. Two conventional farms, one with and one without livestock, served as controls in each of the two areas. In this paper results from the biodynamic farm in Sörmland are presented. Changes in soil mineral nitrogen, nitrogen uptake by the crop and productivity were studied in relation to previous crops, crop rotations, and nitrogen fixation. A nitrogen balance and flow of nitrogen in the farm ecosystem is presented. For a farm to meet its nitrogen needs without resorting to the use of artificial fertilizers requires that nitrogen be effectively recycled within the farm with only small losses; that enough nitrogen-fixing crops be cultivated (legumes on a third of the area in the circulation); and that the intensity of livestock management is adjusted on the basis of the farm's feed production capacity.

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754616

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Growth, nodulation, nitrogen fixation and transfer of N2were studied in a mixed cropping system of cowpea (Vigna unguiculataL. (Walp)) and rice (Oryza sativaL.). The treatments consisted of three cropping systems which were: monocrop cowpea, monocrop rice and cowpea/rice mixed cropping.l5N-labelled ammonium sulphate (20 kg N ha−lof atom %l5N excess) was applied evenly in solution to thel5N subplots while the same amount of unlabelled ammonium sulphate was applied in salt form to thel4N subplots. The cropping system, either sole or mixed with rice, did not significantly influence nodule dry weight at any of the sampling dates. Plants of sole cowpea had a higher shoot dry weight than mixed-crop cowpea plants while the growth of rice was essentially the same. Sequential harvests made at 25, 35, 45 and 55 days after planting (DAP) showed that the proportion of nitrogen derived from N2fixation and the amount of N2fixed by sole and mixed-crop cowpea were similar. Thel5N enrichment data show no clear evidence of significant N2transfer in the cowpea/rice mixed cropping system. The fact that the15N enrichment in the mixed rice was not significantly different from that of sole rice suggests that the15N enrichment in the mixed rice was not diluted by fixed N2from cowpea.

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754617

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Polyethylene (PE) films having various Blue/ultraviolet (B/UV) ratios (20.4–76.8) of the transmitted light have been investigated with regard to their effects on the epidemiology of grey mould in artificially-inoculated greenhouse-grown tomato plants and onin vitrosporulation ofBotrytis cinereaPers. ex Fr. The highest number of infection sites was found on plants grown under the sheet having the lowest ratio of B/UV transmittance (20.4) in both control or artificially-inoculated and fungicide-treated (Rovral) greenhouses. It was also found that the rate of development of the epidemic in greenhouses covered with an improved sheet having a higher ratio of B/UV transmittance (32.7) was remarkably slower as compared to those covered by sheets with a low B/UV ratio. When experimental sheets having even higher B/UV ratio (up to 76.8) were tested, a clear negative association was observed between B/UV ratio and number of spores produced in culture. Such films are suggested as a cladding material for both conventional and organic greenhouse crops where the grey mould disease is a major economic problem.

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754618

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Compost (C), chicken manure (M), bone ash (BA) and triple superphosphate (TSP) were evaluated as fertilizers for common beans on a P-fixing Andosol from Nicaragua, in a pot experiment. Three different levels, based on phosphorus content, of each fertilizer were used. BA- treatments did not have any major effect on growth of bean plants, probably due to slow dissolution rate of calcium phosphates. The high content of macro- and micro-nutrients in compost and chicken manure in most cases significantly increased the growth of bean plants, enhanced nodulation and increased uptake of P, N, Ca, Mg, S, Mn and Cu as compared to TSP, bone ash and the control. Only the highest level of TSP significantly increased plant growth, nodulation and uptake of major nutrients. Clear correlations were found between dry weight of nodules and N- and S- uptake, concentration of Cu and P and added P. A lower fertilizer level of C, M, and BA resulted in a higher phosphorus utilization efficiency than at higher levels. The effect of TSP was the inverse. The organic manures seemed to have lowered the capacity of the soil to fix phosphorus and increased the availability of macro- and micro-nutrients.

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754619

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754620

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754621

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754622

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754623

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1992.9754614

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor