Search

In this study, a regional irrigation schedule optimization method was proposed and applied in Fengqiu County in the North China Plain, which often suffers serious soil water drainage and nitrogen (N) leaching problems caused by excessive irrigation. The irrigation scheduling method was established by integrating the 'checkbook irrigation method' into a GIS-coupled soil water and nitrogen management model (WNMM) as an extension. The soil water and crop information required by the checkbook method, and previously collected from field observations, was estimated by the WNMM. By replacing manually observed data with simulated data from WNMM, the application range of the checkbook method could be extended from field scale to regional scale. The WNMM and the checkbook irrigation method were both validated by field experiments in the study region. The irrigation experiment in fluvo-aquic soil showed that the checkbook method had excellent performance; soil water drainage and N leaching were reduced by 83.1 and 85.6%, respectively, when compared with local farmers' flood irrigation. Using the validated WNMM, the performance of checkbook irrigation in an entire winter wheat and summer maize rotation was also validated: the average soil water drainage and N leaching in four types of soils decreased from 331 to 75 mm year and 47.7 to 9.3 kg hayear, respectively; and average irrigation water use efficiency increased from 26.5 to 57.2 kg ha mm. The regional irrigation schedule optimization method based on WNMM was applied in Fengqiu County. The results showed a good effect on saving irrigation water, decreasing soil water drainage and then saving agricultural inputs. In a typical meteorological year, it could save >110 mm of irrigation water on average, translating to >7.26 × 10 m of agricultural water saved each year within the county. Annual soil water drainage was reduced to <143 mm and N leaching to <27 kg ha in most soils, all of which were significantly lower than local farmers' flood irrigation. In the mean time, crop yield also had an average increase of 2,890 kg ha when checkbook irrigation was applied. [ABSTRACT FROM AUTHOR]

The article focuses on the concentration and chemical fractions of copper, zinc, nickel and chromium in Japanese andisols, which had accumulated swine composts and chemical fertilizers for six years. The unique properties of andisols including high anion exchange capacity, low bulk density, and high organic matter content may influence the accruement of heavy metals. The potential risks of the aggregation of heavy metals as well as its impact on plant tissues, soils and surface waters are also discussed.