浅析种植绿肥在丰富土壤肥力方面的作用

随着农业的不断发展,我国的农作物产量得到极大提高。前些年,由于化肥使用不当,导致土壤肥力降低、土地结块、农作物产量降低等,为了有效改善这些情况,我国开始实施种植绿肥的推广,使土壤肥力得到极大的改善。重点分析了种植绿肥在丰富土壤肥力方面的重要作用。

Higher Species Diversity Occurs in More Fertile Habitats Without Fertilizer Disturbance in an Alpine Natural Grassland Community

Are there some relationships among species diversity and soil chemical properties of high altitude natural grasslands? Plant community composition and chemical properties of soil samples were compared to investigate the relationship between soil and species diversity, and the richness in Tibetan alpine grasslands. Results showed that species diversity was significantly positively related to soil organic matter(SOM), total nitrogen(TN),available nitrogen(AN), total phosphorus(TP),available phosphorus(AP), and available potassium(AK) in the high alpine grasslands. Margalef's species richness index was also significantly positively related to SOM, TN, AN, and TP. Most soil chemical properties showed significantly positive correlation with species diversity and Margalef's richness index.Our results suggested that higher plant species richness index and diversity occurred in more fertile soil habitats in high altitude natural grassland community. In practice, fertilization management for the restoration of degraded grassland should be conducted with reference to the nutrient levels ofnatural grassland without the additional artificial fertilizer and with higher species-diversity and richness index.

Herbage Production and Species Richness in Sub-alpine Grasslands of Different Soil Parent Material in Northern Greece

Several abiotic and biotic factors were investigated as possible predictors of local species richness in two sub-alpine grasslands of Jenna and Belles Mountains in Northern Greece.For species richness modelling a hierarchical modelling framework based on generalized additive models was adopted.The two sub-alpine grasslands differed in aspect,altitude and soil parent material(volcanic origin,mostly trachyte,and andesite(TA) for Jenna and metamorphic rocks,mostly gneiss(G) for Belles).12 fenced squared plots,16 m2 each,were used per grassland,where soil properties,herbage production,species presence and cover of grasses,legumes and forbs were estimated.Mean herbage production was significantly affected by slope and altitude,soil K content and floristic composition as expressed by an ordination axis.Soil p H,floristic composition and average herbage production were significant predictors of forbs and total species richness.For the former,soil N content and for the latter the occurrence of Agrostis capillaris,were also included as significant terms in the predictive model.Thepredictors for grasses species richness were N content,having a positive effect,and average herbage production.In all cases higher species richness was predicted for intermediate values of average herbage production.Differential responses were found between forbs and grasses.The predictors of their species richness were different while for the case of the common predictor(N) the responses of the two groups were also different(grasses species numbers increase and forbs species numbers decreased with increasing N).Maximum species richness of grasses was observed at relatively low production levels while forbs species richness maximized at relatively high production levels.

古代景芝的酿酒生态与酒史辨析

丰富度高的土壤微生物霉菌菌群和酵母菌群及其湿润共生态水体环境有利于酒精发酵,红陶尖底缸的出土佐证了五千年发酵酿酒史,元代蒸馏技术的改进使我国早期的高粱蒸馏酒诞生。

Contribution of Root Proliferation in Nutrient-Rich Soil Patches to Nutrient Uptake and Growth of Maize

Root proliferation can be stimulated in a heterogeneous nutrient patch; however, the functions of the root proliferation in the nutrient-rich soil patches are not fully understood. In the present study, a two-year field experiment was conducted to examine the comparative effects of localized application of ammonium and phosphorus (P) at early or late stages on root growth, nutrient uptake, and biomass of maize (Zea mays L.) on a calcareous soil in an intensive farming system. Localized supply of ammonium and P had a more evident effect on shoot and root growth, and especially stimulated fine root development at the early seedling stage, with most of the maize roots being allocated to the nutrient-rich patch in the topsoil. Although localized ammonium and P supply at the late stage also enhanced the fine root growth, the plant roots in the patch accounted for a low proportion of the whole maize roots in the topsoil at the flowering stage. Compared with the early stage, fine root length in the short-lived nutrient patch decreased by 44%-62% and the shoot dry weight was not different between heterogeneous and homogeneous nutrient supply at the late growth stage. Localized supply of ammonium and P significantly increased N and P accumulation by maize at 35 and 47 days after sowing (DAS); however, no significant difference was found among the treatments at 82 DAS and the later growth stages. The increased nutrient uptake and plant growth was related to the higher proportion of root length in the localized nutrient-enriched patch. The results indicated that root proliferation in nutrient patches contributed more to maize growth and nutrient uptake at the early than late stages.