H. Vogtmann

Accumulation of Nitrates in Leafy Vegetables Grown Under Contrasting Agricultural Systems

ABSTRACT In the framework of the problem of nitrates in food and water, experiments with leafy vegetables are described and the results are presented. In pot and field trials with spinach, Swiss chard, head lettuce and corn salad it was found that fertilizing with composted farmyard manure—a slow release N-source—led to significantly lower nitrate concentrations in these vegetables compared to an N-equivalent NPK-application. These results were supported by similar findings for head lettuce, when the products of 7 paired conventional and biological growers were analyzed. The results indicate a very low risk of high nitrate concentrations in vegetables even with an overdose of composted farmyard manure (300 kg N/ha). Generally, the yields of vegetables grown with compost were lower than those with NPK fertilizers. However, if the right varieties are chosen, similar yields can be obtained. This was clearly demonstrated with two different varieties of spinach. The importance of variety was also demonstrated ...

Compost quality: Physical characteristics, nutrient content, heavy metals and organic chemicals

Bio‐ and yard waste composts show a high standard of quality. Due to their valuable characteristics it is possible to utilize them in plant production. Average heavy metal contents of bio‐ and yard waste composts is low. Nevertheless, the results presented reveal that nine biocomposts do not comply with the requirements necessary to obtain the “seal of approval for quality compost”;. A first check of the data suggests that soil contamination of geological, respectively pedological origin, is responsible for limit violation. Other limit violations are due to increased soil contaminant levels, caused by anthropogenic activities. Increased heavy metal contents in two more composts is likely due for above average degree of undesirable materials in the separately collected organic refuse. Dioxins can be found ubiquitously in the environment, consequently therefore in composting raw material and in the end product. According to current knowledge, levels of PCDD/F found in bio‐ and greencompost can be classified...

Technology and undesirable components on compost of separately collected organic wastes

Abstract The pilot-project “Green Garbage Can” included the separate collection and composting of biogenic wastes from households, gardens and industries in a city of 18 000 inhabitants. The aim of the project was a reduction of the total amount of wastes and the production of compost of better quality as compared with the previously produced municipal-waste compost (+ slurry). A decentralized system with low-cost technology was established, which allowed processing of biogenic waste under controlled conditions. The results demonstrate that under practical conditions, controlled composting will lead to a final product of better quality, with regard to the contents of undesirable components. Environmental pollution owing to run-off or odour can be minimized using appropriate technologies.

The Nitrate Content of Vegetable and Salad Crops Offered to the Consumer as from “Organic” or “Conventional” Production Systems

ABSTRACT This paper briefly reviews the source and extent of ingested nitrates in the human diet. In response to the possible health risk, several countries in Europe have set maximum and/or recommended concentrations of tissue nitrate in vegetables and salad crops. The consequence of adopting such limits in Great Britain is considered. In order to assess the range of nitrate concentrations in vegetables and salad crops, a market survey was conducted over two winters (1985 and 1986) with samples being taken from commercial outlets. Food offered as conventionally and organically produced was sampled. Samples of both organically and conventionally produced leafy winter vegetables contained high nitrate levels, some exceeding recommended and maximum levels in certain European countries. Various approaches to the minimisation of the dietary intake of nitrate are discussed.

Effects of composted FYM and a compound fertiliser on yield and nitrate accumulation in three summer lettuce cultivars grown in an organic system

Abstract This paper reports the results of a trial studying the accumulation of nitrate in 3 varieties of lettuce grown outside and fertilised with composted farm yard manure (FYMC) or with readily soluble compound fertiliser. Three rates of nitrogen application were used equivalent to 0, 80 and 160 kg N ha −1 . There was no significant difference in nitrate accumulation among varieties. Doubling the level of nitrogen applied (from 80 to 160 kg N ha −1 ) had no consistent or significant effect on the amount of nitrate accumulated in the plant tissue. There was a significant effect of fertiliser treatment on nitrate accumulation, with lettuce plants accumulating more nitrate when fertilised with readily soluble compound fertiliser (1410 ppm and 1387 ppm nitrate in fresh weight at 80 and 160 kg N ha −1 , respectively) compared with FYMC (1184 ppm and 1191 ppm nitrate in fresh weight at 80 and 160 kg N ha −1 , respectively). Fertilisation with FYMC did not significantly increase nitrate accumulation when compared with a zero fertilised control (1051 ppm nitrate in fresh weight). Yield was increased by fertilisation, there being no significant difference between composed FYM and compound fertiliser treatment on yield at the high rate of nitrogen application.

Nutrient value and utilization of biogenic compost in plant production

Abstract The nutrient value of biogenic waste compost (BWC) for plant production was determined by chemical analyses and in a field experiment with kohlrabi (Brassica oleracea Gongylods). The results showed favourable nutrient contents of BWC and indicated that it can be used successfully, directly or in combination with chopped bark in various fields of plant production.

Quality of food plants grown with compost from biogenic waste

Abstract Compost from biogenic waste was applied at various levels to tomatoes, beetroots and cabbage. NPK fertilizer or commercial culture substrate were used for comparison. The parameters tested were: desirable and undesirable nutrients in plant products; storage quality: sensory properties. Yields varied depending upon fertilizer applied. However, with regard to storage quality (“store-tests”) and desirable (Vitamin C, sugars) as well as undesirable nutrients (e.g. nitrates), the compost treatments led to superior results. In a number of cases, differences in sensory properties also occurred. Besides the classical methods for the determination of the quality, the newly developed technique of “Biophotones” (luminescence) was also applied to cabbage and led to conclusive results.

Vesicular-Arbuscular Mycorrhiza in Varieties of Winter Wheat in a Low External Input System

ABSTRACT Vesicular-arbuscular mycorrhiza (VAM) can improve phosphorus uptake of wheat plants and may be very effective in agricultural low external input systems, where low concentrations of plant available P are often found in the soil. Levels of VAM-infection were studied in four varieties of winter wheat of different periods of release from 1985 to 1986. These varieties differed greatly concerning rooting patterns and above ground development. Average levels of infection were 22.3% infected root length in May, 41.9% in June, and 50.0% in July. Significant varietal differences in VAM-infection were evident only during milk development stage of the wheat grains in 1986, while no differences at all existed in June of both years. The results are discussed concerning P content of soil and plants, and final phosphorus uptake and dry matter production of winter wheat. It is concluded that a low availability of soil P was counterbalanced to some extent by a strong VAM-infection before the grain filling period....

Case Studies on Nitrate Leaching in Arable Fields of Organic Farms

ABSTRACT Nitrogen supply of crops on organic farming systems mainly depends on mineralization of soil organic matter nitrogen. Mineralization was studied by taking soil samples from 30 plots in the crop rotation of two organic farms at intervals of 7 to 14 days during the growing season. On fallow plots net-mineralization alternated with net-immobilization three times from April to November. These soil inherent dynamics were modified by cultivation and the growing cycles of the different crops. Several cases could be observed which led to high accumulations of leacheable nitrate in soils: 1. fallow during growing season, 2. fallow during autumn and winter, 3. manuring in autumn, 4. leaching of chopped green manure by rain, 5. low nitrogen uptake of crops because of diseases, 6. transfer of mineralizable nitrogen from spring to autumn. The concept of the soil merely as a storage place for plant nutrients was one of the main factors for mistakes in nitrogen management. Understanding the interactions of plan...

Marketing and Pricing of Biological Products in West Germany. A Comparative Study

ABSTRACT The marketing and pricing of biological products compared to conventionally produced food was investigated in southern Germany. 42 farmers (14 conventional, 14 bio-dynamic, 14 organic- biological) were surveyed. Four alternative marketing channels were examined. In contrast to conventional farms direct-marketing plays a major role in biological farms. The prices varied considerably within and between the different farming systems. By and large higher prices for biological products were only obtained for plant products. Occasionally premium prices for biological dairy products are possible. A “food-basket” calculation indicates that costs for the consumer of biological products purchased directly would be about 30% higher, which amounts to a 3% increase in total family expenditure. It is argued that the viability of biological farms cannot be calculated on the basis of retail prices.