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Winter wheat (Triticum aestivum L.) is the major crop in the North China Plain (NCP). The monsoon climate in this region causes most rain to fall in the summer season, but during the winter?wheat growing season (October–May) the rainfall is far less than the water requirements for the crop. The efficiency of soil water use by winter wheat needs to be improved to reduce the need for irrigation. In this paper, we report the results of two seasons'' work on soil water utilization, root growth and distribution, root water uptake by the crop under different irrigation treatments, and possible ways to improve soil water?use efficiency. The field experiments were carried out at Luancheng Station (37° 53?N, 114° 41?E) from 1996 to 1997 and 1998 to 1999, two growing seasons of winter wheat. Five treatments for each season: rain?fed and irrigated winter wheat with different irrigation numbers from 1 up to 4, were set up in a randomized plot design. Soil available water?holding capacity at the experimental site was about 454 mm for the top 2 m soil profile. Root sampling results showed that winter wheat had a prolific root system with an average maximum rooting depth of 2 m. Most of the root system was concentrated in the upper 40 cm of soil. Root length density in the top layer of soil (0–20 cm) was very high, with values over 5 cm cm?3. The distribution of water uptake from the soil profile under high soil moisture conditions was the same as the distribution of root length density. The roots in the top layer of soil played an important role in soil water uptake. When root length density was less than 0 · 8 cm cm?3, the root was the main factor limiting the complete utilization of soil water by crops. The scarcity of roots in the deep soil layers restricted the full utilization of soil water by the crops. Thus, at maturity, over 100 mm of available water remained in the root zone for the rain?fed treatment, although the upper layers had already entered water deficit. The crop took up 80% of the total available soil water in the treatment without irrigation in a dry season. For irrigated wheat, from 40 to 50% of crop water uptake was from the stored soil water. Available stored soil water played an important role in the higher production of wheat crops in the NCP. Effective measures to increase the utilization of stored soil water could improve crop performance under conditions of limited water supply. Results showed that deep tillage to break the soil pan improved root growth in the deeper soil layers, and sowing the crop evenly also enhanced water uptake from the top soil layer to compete with soil evaporation. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the soil water movement in shallow groundwater areas in Cangzhou (CZ) and Hengshui (HS) of Hebei province in the North China Plain, China. It states that North China Plain is considered as the center of politics, economics, and culture in the country. However, it faces great difficulties in water supply and water pollution. It mentions that in the shallow groundwater areas, precipitation infiltration and evaporates are the major processes for the water cycle. The study suggests that although the two sites shared the same climate, there are noted differences in the infiltration process, soil water movement, and groundwater recharge sources.

The article reports on the study using climatic variables for the estimation of the evapotranspiration which is important for detecting crop water status and proper irrigation scheduling in the wheat field in the North China Plain in China. The method is simplified from the Penman-Monteith equation which requires canopy resistance which is used to calculate sensible heat flux and then the latent heat flux as the residual of the surface energy balance. The result reveals that original modified Todorovic model underestimates the canopy temperature and the sensible heat flux and overestimates the latent heat flux.

Growing demand on groundwater resources and the semi-arid climate in the North China Plain (NCP) highlight the need for improved understanding of connections between regional climate change and groundwater recharge. Hydrologic time series of precipitation and groundwater levels were analyzed in three representative geographical zones throughout the NCP for the period of 1960-2008 using trend analysis and spectral analysis methods. A significant change point around 1975 is followed by a long-term decline trend in precipitation time series, which coincides with the Pacific Decadal Oscillation positive phase. However, the magnitudes of groundwater level variability due to heavy pumping overwhelm the low-frequency signal of groundwater levels. Nonlinear trends that related to long-term climatic variability and anthropogenic activities are removed by using the Singular Spectrum Analysis method. Spectral analyses of the detrended residuals demonstrate significant short-term oscillations at the frequencies of 2-7 years, which have strong correlations with the El Niño-Southern Oscillation modes. This study contributes to improved understanding of dynamic relationship between groundwater and climate variability modes in the NCP and demonstrates the importance of reliable detrending methods for groundwater levels that are affected greatly by pumping. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]