[Availability Changes in Different Exogenous Selenium Fertilizers in Soil and Their Effects on Selenium Accumulation in Wheat].

In order to understand the differences in the uptake and accumulation of several common exogenous selenium fertilizers by crops, a wheat pot experiment was conducted to study the availability changes in different selenium fertilizers (potassium selenate, potassium selenite, EDTA-chelated selenium, selenium powder, fly ash, and selenium-enriched straw) in soil and their effects on wheat growth and selenium uptake and distribution. The results showed that the change in availability of different exogenous selenium types in soil was different. During the whole growth period of wheat, the soil available selenium proportion of selenate, selenite, and EDTA-chelated selenium treatment was significantly higher than that of the control (CK), respectively, but there was no significant difference between the other treatments and the CK treatment. In the early stage of wheat growth, the soil available selenium proportion of selenate, selenite, and selenium powder treatment decreased gradually and tended to be stable in the later growth stage of wheat; however, the soil available selenium proportion of other exogenous selenium treatments showed a dynamic change of decreasing in the early period and increasing in the late period. The available selenium content in soil significantly affected the selenium uptake by wheat, and there was a significant positive correlation between them. Selenate application significantly increased the grain and leaf biomass of wheat, but other selenium fertilizers had no significant effect on wheat growth. The accumulation capacity of different exogenous selenium fertilizers for wheat followed the order of selenate>selenite, EDTA-chelated selenium>selenium powder, fly ash, and selenium-enriched straw. There was no significant difference between the selenium powder, fly ash, and selenium-enriched straw treatments and the CK treatment. Selenium was more easily transferred to and accumulated in the stems and leaves of wheat after the application of selenate, whereas selenium was more easily transferred to and accumulated in grains after the application of selenite and EDTA-chelated selenium.

Differential responses of soil nematode community to pig manure application levels in Ferric Acrisols.

Excessive pig manure application probably degrades arable soil quality in some intensive pig farming areas. The responses of the nematode community to dosages of pig manure were investigated in Ferric Acrisols under 3-season peanut monoculture. Varying dosages of manure (1.75, 3.5, 7, 14 and 28 t·ha-1·yr-1) in combination with chemical fertilizer were applied to field plots, and chemical fertilizer alone was also applied as a control. With increasing manure application, the abundance of bacterivores and omnivores-predators increased, the abundance of plant parasites decreased, and fungivores abundance exhibited hump-shaped variation. Simpson diversity index and plant parasite index/maturity index of the nematode communities increased to a maximum level at a manure application rate of 3.5 t·ha-1·yr-1 and then sharply decreased. The changes in the soil nematode community were further determined to be correlated with chemical properties; available phosphorus had the strongest quadratic correlation with the two indices, implying that available phosphorus had a better indicative effect than other soil properties to nematode community. Available phosphorus in soil was deduced from 49 to 64 mg·kg-1 with the best nematode communities. Our results emphasized the importance of regular applications of manure in agriculture field to balance nematode diversity and build healthy agro-ecosystems.