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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 loess region in northern China is an important area of apple ( Pyrus malus L.) and pear ( Pyrus communis L.) production due to its favorable soil and climate. In recent years, as the apple and pear production in this region rapidly increased, more orchards experienced iron deficiency chlorosis. However, information on soil nutrient status and fruit tree chlorosis of this region is scarce. In this research, we collected soil and fruit tree leaf samples from 25 pear and apple orchards (10 chlorotic orchards and 15 nonchlorotic orchards). Soil samples were collected at depths of 0–20 cm, 20–40 cm, 40–60 cm, and 60–80 cm. Soil organic matter, total nitrogen (TN), alkali-hydrolyzable N, Olsen-phosphorus (P), ammonium acetate-potassium (K), DTPA-iron (Fe), and less than 0.01-mm soil particle content were analyzed, soil bulk density of 0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm were also determined. Leaf samples were analyzed for chlorophyll content. Comparison of soil properties was performed between chlorotic orchard soils and nonchlorotic orchard soils; stepwise multiple regression was performed between leaf chlorophyll content and soil properties. The results indicated that those orchard soils were rich in P and K but deficient in Fe. Chlorotic orchard soils contained more K, bicarbonate and less than 0.01-mm soil particles, and less DTPA-Fe in certain layers than those of nonchlorotic orchard soils. Leaf chlorophyll content negatively correlated with soil bicarbonate, alkali-hydrolysable N, and ammonium acetate-K and positively correlated with TN, DTPA-Fe, and bulk density at certain depths. Most of these soil properties that have a significant difference between these two kinds of orchard soils or affect leaf chlorophyll content occur below 40 cm in the soil profile. These results suggested that high bicarbonate content and low available Fe content in soils were the primary causes for fruit tree chlorosis in the loess region. Shallow groundwater table in the chlorotic orchards and root growth impairment in the surface soil because of tillage are supposed to be the reason why deeper depth in soil profile play an important role in fruit tree chlorosis in this region. [ABSTRACT FROM AUTHOR]