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471.
Soils are a major source of atmospheric NO and N2O. Since the soil properties that regulate the production and consumption of NO and N2O are still largely unknown, we studied N trace gas turnover by nitrification and denitrification in 20 soils as a function
of various soil variables. Since fertilizer treatment, temperature and moisture are already known to affect N trace gas turnover,
we avoided the masking effect of these soil variables by conducting the experiments in non-fertilized soils at constant temperature
and moisture. In all soils nitrification was the dominant process of NO production, and in 50% of the soils nitrification
was also the dominant process of N2O production. Factor analysis extracted three factors which together explained 71% of the variance and identified three different
soil groups. Group I contained acidic soils, which showed only low rates of microbial respiration and low contents of total
and inorganic nitrogen. Group II mainly contained acidic forest soils, which showed relatively high respiration rates and
high contents of total N and NH4
+. Group III mainly contained neutral agricultural soils with high potential rates of nitrification. The soils of group I produced
the lowest amounts of NO and N2O. The results of linear multiple regression conducted separately for each soil group explained between 44–100% of the variance.
The soil variables that regulated consumption of NO, total production of NO and N2O, and production of NO and N2O by either nitrification or denitrification differed among the different soil groups. The soil pH, the contents of NH4
+, NO2
– and NO3
–, the texture, and the rates of microbial respiration and nitrification were among the important variables.
Received: 28 October 1999 相似文献
472.
473.
Rapidly expanding global aquaculture requires sustainable, local protein sources to supplement the use of fishmeal. Lupin seed meal (Lupinus angustifolius) was tested as sustainable diet component for Whiteleg shrimp (Litopenaeus vannamei). Controlled feeding experiments were conducted in a recirculating aquaculture system for eight weeks. Juvenile shrimps were provided formulated diets containing various levels of lupin meal inclusion (0, 100, 200 and 300 g kg?1) supplementing the fishmeal component, and a commercial feed as general reference. Shrimp survival, growth, metabolic and immune parameters were analysed. Survival did not differ significantly between groups. Growth performance was significantly impaired in shrimp fed diets containing more than 100 g kg?1 lupin meal. Lupin meal supplementation did not affect haemolymph protein content, whereas glucose and acylglyceride concentrations varied between treatments and were highest in animals fed the 100 g kg?1 lupin meal diet. Phenoloxidase activity was highest in shrimp fed 100 g kg?1 lupin meal diet indicating improved immune status. The present study indicates that low inclusion levels of lupin meal do not cause adverse effects and seem to stimulate the immune system of juvenile L. vannamei. 相似文献
474.
The correct diagnosis of boron deficiency is not yet completely resolved for species where boron is phloem immobile. As some deficiency reactions in the extension zone of young roots cannot be reversed after only one hour of deficiency, boron should be supplied continuously. Several early deficiency reactions are shown to be related to the concentration of ”︁free” boron. It is suggested that there is a ”︁minimum” or ”︁critical level” of soluble boron (i.e. not tightly bound to rhamno‐galacturonan II) which is needed in the most boron requiring tissues to avoid deficiency reactions. Determination of this ”︁soluble” or ”︁exchangeable” boron fraction might improve the diagnosis of boron deficiency. 相似文献
475.
Muhammad Ayaz Urte Stulpinaite Dalia Feiziene Vita Tilvikiene Kashif Akthar Edita Baltrėnaitė-Gedienė Nerijus Striugas Urooj Rehmani Sahib Alam Rashid Iqbal Monika Toleikiene Modupe Doyeni 《Soil Use and Management》2022,38(2):1307-1321
Management of heavy metal-contaminated soil under drought and other harsh hydrological conditions is critical for protecting soil ecosystem services. In this study, we examined the effect of pig manure digestate-derived biochar as a soil amendment (15 t ha−1) with N fertilizer (180 kg ha−1) on soil and plant heavy metal levels and nutrient availability under various moisture regimes (optimal moisture ~15%, drought condition ≤5%, and flooded condition ≥35% wt.). It was observed that biochar applications significantly decreased heavy metals in the spring wheat plants, lowering Cr by 90%, Ni by 50%, Cd by 9% and Pb by 34% compared to non-biochar (control) treatments. However, the pig digestate-derived biochar increased heavy metals in soil under all moisture regimes, increasing soil Cr by 21%, Ni by 43%, Cu by 55%, Zn by 70%, and Pb by 12%. The availability of macroelements also increased with the biochar applications under the optimum moisture regimes in both soil and plants, increasing Mg2+ by 11%, P by 4%, K+ by 50%, and Ca2+ by 56% in the soil, and Mg2+ by 13%, P by 69%, K+ by 29, and Ca2+ by 39% in plants. Biochar addition also improved chlorophyll fluorescence (CF) levels in the crop for the entire season (12th to 62nd day) and the aboveground crop biomass and dry matter contents both increased. Consequently, the use of pig manure digestate-derived biochar with N fertilizer under normal moisture conditions was able to reduce heavy metal availability to plants and thus could be used in contaminated soils to maintain better crop growth and development. 相似文献