摘要:

The influence of the time of inoculation with an indigenousRhizobiumstrain on biological nitrogen fixation in soyabean was tested in a field experiment in Greece, in an area extremely low in indigenousRhizobiaeffective on soyabean. Inoculation was either at sowing by seed inoculation or 30 days later with liquid solution. One nodulating and one non-nodulating variety ofGlycine max(L.) Merr., were used, while the contribution of the low indigenousRhizobiumpopulation was measured with uninoculated plants of the nodulating variety. Nitrogen fertilizer labelled with15N enabled the nitrogen derived from fixation (% NdfF), from fertilizer (% Ndff) and from the soil (% Ndfs) to be estimated.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755226

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study was carried out in one of the plots at the Gambari Experimental Station (GES) jointly initiated by the Cocoa Research Institute of Nigeria (CRIN) and the Nigerian Institute of Oil Palm Research (NIFOR) in 1965. The experimental design, mainly agronomic, was randomized blocks consisting of three spacing arrangements: pure stands of cocoa and oil palm; avenue planting of cocoa and oil palm and hollow square planting of cocoa and oil palm.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755227

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Leaching of nitrogen from arable land is an important factor contributing to increased nutrient loads to lakes and coastal waters. The aim of this study was to evaluate the impact of ley composition and time of incorporation on the nitrogen utilization by subsequent winter- or spring-sown crops and risks for nitrogen leaching. Therefore, a field investigation was carried out, using a split-plot design. Ten treatments with different preceding crops were used, i.e. five compositions of forage ley, three green manure treatments and two treatments with spring barley. Also three different times for incorporation of the crop residues were used (early autumn, late autumn or spring). No supplements of commercial fertilizer-N or manure were applied. The average grain yields were strongly influenced by the amounts of nitrogen in incorporated material. Early autumn incorporation gave acceptable grain yields, but rather large amounts of soil mineral nitrogen were found in late autumn which had disappeared before early spring, probably due to leaching. Late autumn and spring incorporation were both good choices with respect to reducing risks for leaching during the first winter and had positive effects on subsequent grain yields. Incorporation of ley residues in late autumn and in spring caused increased mineral-N content in soil during the following autumn.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755228

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper reviews the environmental effects of organic farming, with particular reference to Australia but using some international experience as well as findings from other ‘alternative’ farming systems where appropriate. Beneficial environmental effects include positive changes to soil physical, biological and chemical properties in comparison with some adverse effects associated with conventional agriculture. Other benefits are linked to the opportunities provided to recycle organic wastes, the reduced use of synthetic chemicals, improvements to plant and animal quality, reductions in erosion and runoff, and potential improvements to the serious problems of soil and water salinity and the loss and deterioration of ecosystems.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755229

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Fertilization of ecological cultivating systems for producing greenhouse tomatoes with locally produced mulches was studied from 1993 to 1995. The tomato plants were cultivated in limited growth beds filled with nutrient-poor substrate, consisting of farmyard manure (FYM) compost, straw and soil subsequently mixed with peat and gypsum. Mulches of freshly cut grass or clover or a mixture of the two were placed on the surface of the substrate to assess their value as fertilizer. Fruit yield, fruit quality, plant length and NPK-content of mulch materials and bed water were regularly measured. Comparisons made on four occasions during each growing season showed that the mulches containing clover produced significantly higher yield than the grass mulch and this treatment also had the best utilization of P and K. Nitrogen utilization was highest in beds fertilized with grass mulch, even though the yield was lower. Combined mulch of grass and clover produced intermediate yield and had good utilization of N, P and K. However the clover-grass mulch seemed to have potential for higher yield than was found in the experiment.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755230

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In field experiments with drilled salad onions, a single weeding made at 4 weeks after 50% crop emergence was sufficient to prevent significant yield loss due to weeds. Weed removal 5 or 6 weeks after 50% crop emergence was generally unsuccessful in averting crop losses. It is well known that the relative timing of crop and weed emergence is important in determining the balance of crop-weed interactions. In the present experiments, the pattern of crop and weed emergence varied between sites and years but the removal of early emerging weeds, at 4 weeks after 50% crop emergence, avoided weed interference consistently. In the transplanted bulb onion experiments, the crop began with an advantage over the weeds, and a single weeding made at 5, 6 or 7 weeks after planting was effective in preventing a reduction in yield. There was no difference in response between crops grown organically and those grown conventionally. Yield loss was due mainly to weed competition occurring prior to handweeding or mechanical injury to the crop following late or repeated weed removal. In the conventional crop, a single weeding that removed inter-row weeds but left within-row weeds in place gave yields little better than those of the unweeded crop.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755231

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Changes in the soil weed seedbank were monitored over a single growing season in field experiments with drilled salad onion and carrot crops following different weeding treatments. Viable weed seed numbers were determined in soil samples taken at crop sowing and at harvest. When the crops were left weedy until harvest, seed numbers in soil increased by between two- and seventy-fold due to the influx of fresh seed. There was much less change in weed seed numbers in the soil when crops were kept weed-free until harvest or weeded once at 4, 5 or 6 weeks after 50% crop emergence. An estimate of the seedbank at harvest in the weeded treatments as a proportion of that of the unweeded control was derived using a log-linear model that included a covariate adjustment for seed numbers at sowing. There was little difference in the proportion remaining when crops were weeded once or kept weed-free throughout. The results were similar in carrot and salad onion crops grown in organic or conventional cropping systems. The findings highlight the risk of a rapid increase in the soil seedbank if weed control is neglected in a single crop. However, there was no indication that limiting weed control to one carefully-timed weeding would increase the potential weed population in subsequent crops.

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755232

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755233

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755234

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.1998.9755235

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor