Yonggan Zhao

Buried straw layer and plastic mulching increase microflora diversity in salinized soil

Salt stress has been increasingly constraining crop productivity in arid lands of the world. In our recent study, salt stress was alleviated and crop productivity was improved remarkably by straw layer burial plus plastic film mulching in a saline soil. However, its impact on the microflora diversity is not well documented. Field micro-plot experiments were conducted from 2010 to 2011 using four tillage methods: (i) deep tillage with plastic film mulching (CK), (ii) straw layer burial at 40 cm (S), (iii) straw layer burial plus surface soil mulching with straw material (S+S), and (iv) plastic film mulching plus buried straw layer (P+S). Culturable microbes and predominant bacterial communities were studied; based on 16S rDNA, bacterial community structure and abundance were characterized using denaturing gradient gel electrophoresis (DGGE) and polymerase chain reaction (PCR). Results showed that P+S was the most favorable for culturable bacteria, actinomyces and fungi and induced the most diverse genera of bacteria compared to other tillage methods. Soil temperature had significant positive correlations with the number of bacteria, actinomyces and fungi (P<0.01). However, soil water was poorly correlated with any of the microbes. Salt content had a significant negative correlation with the number of microbers, especially for bacteria and fungi (P<0.01). DGGE analysis showed that the P+S exhibited the highest diversity of bacteria with 20 visible bands followed by S+S, S and CK. Moreover, P+S had the highest similarity (68%) of bacterial communities with CK. The major bacterial genera in all soil samples were Firmicutes, Proteobacteria and Actinobacteria. Given the considerable increase in microbial growth, the combined use of straw layer burial and plastic film mulching could be a practical option for alleviating salt stress effects on soil microbial community and thereby improving crop production in arid saline soils.

Rotary tillage in rotation with plowing tillage improves soil properties and crop yield in a wheat-maize cropping system

Soil rotational tillage is an effective measure to overcome the problems caused by long-term of a single tillage, but the effect of the interval time of rotational tillage practices is not very well understood. Therefore, we conducted a 3-year field study in a wheat-maize cropping system to evaluate the effects of rotary tillage (RT) in rotation with plowing tillage (PT) on soil properties in northern China. Four practices were designed as follows: 3 years of RT to a depth of 10–15 cm (3RT), 3 years of PT to a depth of 30–35 cm (3PT), 1 year of PT followed by 2 years of RT (PT+2RT), and 2 years of PT followed by 1 year of RT (2PT+RT). Within 20 cm of the surface soil, the 3RT treatment significantly increased the soil quality index (SQI) by 6.0%, 8.8% and 13.1%, respectively, relative to the PT+2RT, 2PT+RT and 3PT treatments. The improvement was closely related to the significant increase in the soil organic carbon (SOC) and available nutrients concentrations in the 0–20 cm depths and the improvement of soil invertase, urease, alkaline phosphatase and catalase activities in the topsoil (0–10 cm). However, the opposite effects were observed in the subsoil (20–40 cm). Compared with the 3RT treatment, the 3PT, 2PT+RT and PT+2RT treatments decreased soil bulk density, and significantly enhanced enzyme activities, resulting in an increase in SQI of 32.6%, 24.4% and 0.7%, respectively, especially in the 3PT and 2PT+RT treatments, the difference was significant. When averaged across to all soil depths, the SQI under the 3RT and 2PT+RT treatments was much higher than that under the other treatments. The yields of wheat and maize under the 2PT+RT treatment were 15.0% and 14.3% higher than those under the 3RT treatment, respectively. The 2PT+RT treatment was the most effective tillage practice. These results suggest that RT in rotation with PT could improve soil quality in the soil profile whilst enhancing crop yield after continuous RT, and the benefits were enhanced with an interval time of one year. Therefore, the 2PT+RT treatment could act as an effective method for both soil quality and crop yield improvement in a wheat-maize cropping system under straw incorporation conditions.

Combined application of a straw layer and flue gas desulfurization gypsum to reduce soil salinity and alkalinity

Abstract Burying a straw layer and applying flue gas desulphurization (FGD) gypsum are effective practices to ameliorate soil salinization or alkalization and to increase crop yield; however, little information exists on the effects of such integration in saline-alkali soils. A soil column experiment was conducted to investigate the effects of a straw layer plus FGD gypsum on soil salinity and alkalinity. We placed a straw layer (5 cm thick) at a depth of 30 cm and mixed FGD gypsum into the 0–20 cm soil layer at application rates of 7.5, 15.0, 22.5, and 30.0 t ha−1, with no straw layer and FGD gypsum as a control (CK). The soil water content in the 0–30 cm soil layer was significantly higher (> 7.8%) in the treated soil profiles after infiltration than in the CK, but decreased after evaporation. The electrical conductivity (EC) of the 10–30 cm soil layer was 230.2% and 104.9% higher in the treated soil profiles than in the CK after infiltration and evaporation, respectively, and increased with increasing rates of FGD gypsum application, with Ca2+ and SO2−4 being the main dissolved salts. Compared to those in the CK, the concentrations of Na+, Cl−, and HCO−3 decreased in the treated soil profiles at depths above 55 cm, but the other soluble ions increased, after infiltration. A similar trend occurred after evaporation for all soluble ions except for HCO−3. The pH and exchangeable sodium percentage in the treated soil profiles were significantly lower than those in the CK over the entire profile, and decreased with increasing FGD gypsum application rates. Therefore, the incorporation of a straw layer plus FGD gypsum can reduce salinity and alkalinity, but the quantity of FGD gypsum should be controlled in saline-alkali soils.