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Liu P.,Shandong Academy of Agricultural Sciences | Liu P.,Key Laboratory of Agro Environment in Huang Huai Hai Plain | Zhong Z.,Shandong Academy of Agricultural Sciences | Zhao H.,Shandong Academy of Agricultural Sciences | And 6 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica

Continuous cropping obstacle is a common problem in agriculture and autotoxicity of allelochemicals plays a major role in this problem of many crops. In field situations, allelochemicals (autotoxins) must accumulate and persist at phytotoxic levels and comes in contact with the target plant. The potential of plant allelopathy includes the combined effects of all allelochemicals released. Peanut (Arachis hypogaea L.) is a kind of oil crop and highly vulnerable to continuous cropping obstacle. In a previous study we showed the autotoxic potential of peanut root exudates. We have isolated and identified a number of compounds from the root exudates of peanut seedlings including long-chain fatty acids. Long-chain fatty acids are suggested as a group of potential allelopathic compounds. The object of this study was to discuss the relationship between the accumulation of fatty acids in field soil and peanut continuous cropping obstacle, and offer some new theoretical bases for the mechanism study of peanut continuous cropping obstacle. We investigated the synergetic effects of three long-chain fatty acids (Tetradecanoic, Hexadecanoic and Octadecanoic acids) in the root exudates of peanut (Arachis hypogaea L.) on peanut plant growth, production and soil enzyme activities. A simulation experiment in pot culture was carried out using the field soil as the growth medium. It was found that their low content (80 mg/kg soil) slightly stimulated the growth and production of peanut (P > 0. 05), but their high contents (160 mg/kg soil and 240 mg/ kg soil) significantly decreased the growth and production (P < 0.05). With increasing fatty acid content in the soil, growth of peanut plants was inhibited and the degree of inhibition increased in a dose-dependent manner. At flowering stage when fatty acids were at their highest content (240 mg/kg soil), plant height, shoot fresh weight, root fresh weight and total biomass were reduced by 14. 4%, 22. 0%, 30. 9% and 23. 7%, respectively. When the content of fatty acids was 160 mg/kg soil and 240 mg/kg soil, peanut pod production was significantly decreased by 15.4% (P = 0.021) and 22.4% (P = 0.005), respectively. Chlorophyll content in peanut leaves, root activity, soil enzymes (sucrase, urease and phosphatase) activities were slightly promoted at low content of fatty acids in soil but were suppressed at high conctents (P<0. 001). At the highest fatty acid content (240 mg/kg soil), leaf chlorophyll content and root activity were reduced by 21. 0% and 31.4% at the seedling stage and 22. 7% and 33. 3% at the flowering stage. At the flowering stage, sucrase, urease and phosphatase activities were reduced by 25. 3, 25.4 and 26. 1%, respectively, by fatty acids at their highest tested content (240 mg/kg soil). Decreases in photosynthates production, nutrients uptake and rhizosphere nutrients availability were one of the possible reasons which could decrease the peanut growth and production. The accumulation of three long-chain fatty acids, tetradecanoic, hexadecanoic and octadecanoic acids, in field soil has close relationship with peanut continuous cropping obstacle. Source

Hoogendoorn C.J.,Agresearch Ltd. | Luo J.,Agresearch Ltd. | Lloyd-West C.M.,Agresearch Ltd. | Devantier B.P.,Agresearch Ltd. | And 6 more authors.
Agriculture, Ecosystems and Environment

There is increasing scrutiny of the impact of grazing systems on the wider environment. Urine deposition during grazing has a dominant influence on inorganic nitrogen (N) loss to air and water, and in particular on emissions of nitrous oxide (N2O), a potent greenhouse gas. A series of three field trials were conducted to determine N2O emission factors of urine (EF3: N2O-N emitted as % of urine N applied) from animals on two different forage diets: forage rape (Brassica napus L.) and a conventional ryegrass/white clover (Lolium perenne L./Trifolium repens). Emission factors were measured over two winter trials and one summer trial, using both sheep and cattle urine. All three trials were conducted on a poorly drained soil. It was found that there was a tendency for a higher EF3 for urine from animals on a forage rape diet, both when applied to the forage rape soil and when applied to the pasture soil, although differences were not significant on an individual trial basis. When the data for all three trials was combined in a meta-analysis, urine from forage rape-fed animals had a significantly higher EF3 than urine from pasture-fed animals (1.54 vs. 1.20%). This was despite background emissions from the soil under forage rape being higher than from the soil under pasture. Our results suggest that there may be scope to influence N2O emissions via forage type on offer. © 2016 Elsevier B.V. Source

Liu P.,Shandong Academy of Agricultural Sciences | Liu P.,Key Laboratory of Agro Environment in Huang Huai Hai Plain | Li Y.,Shandong Academy of Agricultural Sciences | Li Y.,Key Laboratory of Agro Environment in Huang Huai Hai Plain | And 7 more authors.
Chinese Journal of Applied Ecology

Data collected from 51 representative greenhouses of Shouguang through questionnaire survey were analyzed to investigate the effect of chemical fertilizers on vegetable yield, relationship between application of organic manure and yield, and influence factors and evolution rule of fertilizer application rate. The results showed that averages of 3338 kg N·hm-2, 1710 kg P2O5·hm-2, 3446 kg K2O·hm-2 were applied to greenhouse vegetables annually in Shouguang, 6-14 times as that in the local wheat-maize rotation system. The application rates of chemical N, P, and K fertilizers accounted for about 35%, 49% and 42% of the total input. Increasing application of chemical fertilizers had no significant effect on vegetable yields, while organic manure input significantly increased the vegetable yields. With the increase of greenhouse cultivating time, no significant changes in the input of chemical N, P, and K fertilizers were observed in greenhouse vegetable production while organic manure input decreased significantly. Differences in vegetable species, planting pattern and cultivating time of greenhouses was one of the reasons for large variations in nutrient application rate. In recent more than ten years, organic manure nutrient input increased significantly, chemical N and P fertilizer input presented a downward trend, chemical K fertilizer input increased significantly, and the N/ P/ K ratio became more and more reasonable in greenhouse vegetable production in Shouguang. Source

Gao X.H.,Shandong Academy of Agricultural Sciences | Zhang Y.P.,Shandong Academy of Agricultural Sciences | Zhang Y.P.,Key Laboratory of Agro Environment in Huang Huai Hai Plain | Liu Z.H.,Shandong Academy of Agricultural Sciences | And 8 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica

Greenhouse farming is one of the important ways to produce vegetables in the world. This technology is characterized by that it may produce high yield of vegetable and would be less affected by the seasons. In addition, it could improve the land-use efficiency and agricultural sustainability in the regions with a large population but not enough arable land. Therefore, it could significantly raise the income of the farmers and was extended quickly in northern China. In China, Shandong province is the major vegetable production region, accounting for nearly 50% in terms of greenhouse area. In recent years, the vegetable production in greenhouse farming system has developed rapidly and brought good economic revenue and social benefits in Shouguang, Shandong Province. Now, Shouguang has been one of the most important vegetable production bases of China and obtained the title “the village of Chinese vegetable”. However, due to the lack of scientific and reasonable fertilization guidance, many problems has also arisen in vegetable production including excessive fertilization nutrient imbalance, and low fertilizer use efficiency, resulting in nutrient accumulation in soil, significant decrease in vegetable quality, and serious deterioration of soil under greenhouse conditions. Thus, the greenhouses for years in some regions are no longer suitable for vegetable production. This situation had brought certain negative impact on the agricultural sustainability, vegetable quality and ecological environment. To examine the effect of different cultivating years on soil ecological environment under the greenhouse conditions, this study was conducted to investigate the differences of soil physical and chemical properties, microflora, and the correlations between cultivating years and soil physic-chemical properties and microbial quantity under the greenhouse conditions. The results showed that with the increase of cultivating years, soil bulk density and pH value were significantly reduced, while the soil porosity, electrical conductivity, soil salt content and organic matter content were significantly increased. The contents of soil total nitrogen and total phosphorus were kept rising. The amounts of total potassium, nitrate nitrogen and available phosphorus in soils increased in the first years, and then followed by a gradual reduction. With the increase of cultivating years, the number of bacteria tended to decrease after a rise in the first years; the number of actinomycetes remained relatively constant after a rapid rise in the first years; only the number of fungi had been continuously increasing. It can be concluded that the large inputs of organic and inorganic fertilizers lead to the soil acidification, nutrient imbalance, a decrease in micro-ecological balance, and significant increases in soil salt content and environmental risk in the greenhouse soils of different cultivating years. Thus, some reasonable and scientific fertilization strategies should be proposed and recommended to the vegetable producers to coordinate the balance between nutrient and energy of soil, improve soil quality and ensure the security of soil ecological environment in greenhouse. Main strategies may include the alteration of the fertilization habit of farmers, reductions in the amounts of nitrogen fertilizers, phosphorus fertilizers and some physiologically acid fertilizers, and properly combined application of organic and inorganic fertilizers. © 2015, Ecological Society of China. All rights reserved. Source

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