摘要:

The recent biological invasion of water hyacinth (Eichhornia crassipes(Mart.) Solms) into lakes and rivers of East Africa has forced the implementation of mechanical harvesting around key harbours and dams, resulting in subsequent difficulties of waste disposal. Utilization of these wastes would assist in deferring costs of control, currently covered by international agencies. This paper reports the nutrient contents, mineralization patterns and potential for ensiling water hyacinth wastes. Whole chopped plants and tissues separated into leaves, petioles and roots were placed into litter bags, deployed as surface mulch or submerged in water and recovered over 16 weeks. The wastes consisted of 45% leaves, 26% petiole and 29% roots and contained 92% moisture. Decomposition was greater under surface mulched conditions and significant differences were observed between plant tissues. The time to 50% decomposition of whole plants was 21 and 74 days for mulched and submerged conditions, respectively. Mineralization of N and P was significantly delayed under anaerobic conditions. Shoots of fresh water hyacinth were chopped into 2 to 4 cm pieces, maize bran or molasses added at rates of 0, 10, 15, 20 and 25% on a fresh weight basis and fermented for 21 days. Without additives, the pH of water hyacinth alone was 7.33, suggesting poor silage quality. Addition of 15% maize bran or molasses resulted in silage of pH 4.1 and 4.2, respectively. Silage prepared with 15% maize bran contained 20% dry weight with 13% crude protein and 20% acid detergent fibre. Water hyacinth silage prepared with maize bran and molasses was readily accepted by goats and young steers. Waste disposal problems may be related to poor aeration within mounds and an alternative exists for use of the wastes as organic inputs to soils or as livestock feed.

ISSN:0144-8765    

DOI:10.1080/01448765.2000.9754841

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Major objectives of this study were to evaluate the effects of organic, conventional and integrated orchard fruit production systems on the quality and quantity of soil organic matter in orchard floors and to identify sensitive soil organic matter indicators. Seventeen different soil organic matter parameters were studied. These were soil aggregate stability (AS), total nitrogen (TN), total carbon (TC), carbon/nitrogen ratio, microbial biomass N (BN), microbial biomass C (BC), BC:BN; BC:TC; BN:TN; hot-water extractable C (HC), hot-water extractable carbohydrate (HCA), HCA:HC; humin N (hum N), humin C (hum C), hum C:TC; hum N:TN and potentially mineralizable N (Pot N). They were based largely on soil organic matter characteristics and fractions extracted sequentially by different extractants from soils collected from the alleys and treelines of organic, conventional, and integrated grassed-down apple orchard types from both commercial and experimental sites in Canterbury, New Zealand. A total of 12 apple orchards were investigated. Soil samples collected from these orchards (0–75 mm depth) were analysed for TC, TN, BC, BN, Pot N, AS and also sequentially extracted for labile and stable soil organic matter fractions using cold and hot water, acid mixtures (hydrochloric:hydroflouric acids, HC1:HF) and alkalis (sodium pyrophosphate and sodium hydroxide, Na4P207and NaOH). Only TN, BN, and BN:TN showed significant interaction effects and all these were associated with soil N. Overall, combining orchards according to similar management systems, results obtained showed no significant differences between experimental and commercial orchards. However, sensitive indicators capable of distinguishing significant differences between different orchard management systems were BC, BC:TC and HCA:HC while HCA:HC distinguished significantly between treelines and alleys within each group of the same orchard type.

ISSN:0144-8765    

DOI:10.1080/01448765.2000.9754842

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A dairy system based on grass-white clover (GC) swards, receiving no artificial nitrogen fertilizer, was established and its physical performance compared with that of a system in which grass only (GN) swards received 350 kg N ha−1year−1. The comparison was made over 3 years using two self- contained Holstein-Friesian herds of 70 cows and replacements. Initially the stocking rate for both systems was 2.4 livestock units ha−1. Grass-clover swards were successfully established and GC herbage ensiled. Total silage yields from GC swards (t DM ha−1year1) were on average 0.87 those of GN swards. Over the three years of the study, grazed sward clover contents were maintained at an average of 25% of total dry matter production over the whole season, and followed a repeatable seasonal increase from an average of 8% in April to 37% in August. Milk yield per cow was within 0.97 of the target of 5700 1 cow−1in each year. However, in years 1 and 2, as a result of the lower herbage yield from GC swards, the level of concentrate required to achieve this was higher in the GC system. In year 3, the stocking rate of the GC unit was reduced to 1.9 livestock units ha−1and equal milk yields were achieved by the two units, with equal concentrate inputs. Although problems are perceived with the use of GC swards, this study has shown that, with appropriate management, GC swards can support a viable dairying system, providing an opportunity for minimizing the use of nitrogen fertilizer.

ISSN:0144-8765    

DOI:10.1080/01448765.2000.9754843

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Conversion from conventional to organic cropping systems was started in 1993 at three sites in Norway: Landvik (Grimstad), Voll (Ås), and Kvithamar (Stjørdal). A six-year crop rotation was designed for each site. At Landvik, the nutrient input was based on compost from plant residues and household waste, and at Voll and Kvithamar, the plant nutrient supply was from cattle slurry. The yields of leys were large at all three sites. At Landvik, large yields of vegetables were obtained. At Kvithamar the yields of cereals were small, while at Voll the growth conditions for cabbage varied between years, causing crop failure in 1995 and a large yield of good quality in 1994. More potassium was removed than applied from the cropping systems at all three sites, but a significant decrease in potassium status of the soil was only found at Landvik. At Voll and Kvithamar, a negative balance was found for phosphorus, and a corresponding significant decrease in readily available P of the soil was found. The nitrogen inputs to the cropping systems were somewhat higher than the amounts of nitrogen removed by the crops. Adjusted for estimated nitrogen leaching, the nitrogen balances were close to equilibrium at Kvithamar and Landvik and negative at Voll. Nitrogen supply seems to be the major factor limiting plant growth in the cropping systems.

ISSN:0144-8765    

DOI:10.1080/01448765.2000.9754844

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

One argument for supporting organic farming has been that it requires more labour and leads to higher rural employment. On the other hand, the high labour costs may constrain the development of the organic sector. This paper reviews the current knowledge about labour use changes in the conversion to organic farming in Western Europe. It discusses how key concepts derived from feminist literature on rural women and agriculture can enlarge the existing knowledge of labour in organic farming which is mainly a product of farm management approaches.

ISSN:0144-8765    

DOI:10.1080/01448765.2000.9754845

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.2000.9754847

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.2000.9754848

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0144-8765    

DOI:10.1080/01448765.2000.9754840

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor