A four-season experiment was carried out in the North China Plain (NCP) to evaluate crop yield and water productivity of winter wheat (Triticum aestivum L.) under sprinkler and surface irrigation. Results show that leaf area index (LAI) of winter wheat was greater and active leaf area lasted for longer in the sprinkler than in the surface irrigated field. Above-ground biomass at harvest was 4~22.1% greater in the sprinkler than in the surface irrigated field, similarly the yield was greater by 11.5~50.9%. The greater yield was mainly due to the greater weight of 1000 kernels in the sprinkler irrigated field. Seasonal crop evapotranspiration (ET) was lower by 4~23%, water productivity (WP) was higher by 18~57% and irrigation water productivity (IWP) was higher by 21~81% in the sprinkler field than in the surface irrigated field. Statistical analysis of four-season data by using a generalized linear model showed that the sprinkler irrigation method significantly increased crop yield, WP and IWP, and significantly decreased crop ET. Crop WP and IWP were also significantly affected by climate conditions and agronomic practices. Therefore, the sprinkler irrigation method was recommended as an efficient and water-saving irrigation method for winter wheat cultivars in the North China Plain. RÉSUMÉUne expérimentation de quatre ans a été réalisée dans la plaine du Nord en Chine pour évaluer le rendement et la productivité de l'eau du blé d'hiver (Triticum aestivum L.) irrigués en gravitaire ou par aspersion. Les résultats d'indice de surface foliaire (LAI) du blé d'hiver montrent que la surface foliaire active est plus importante et dure plus longtemps dans le cas d'irrigation par aspersion. La biomasse aérienne à la récolte était de 4 à 22,1% plus grande dans le cas de l'arrosage par aspersion, de même que le rendement était supérieur de 11,5 à 50,9%. Le meilleur rendement est principalement attribuable à la plus grande fois de 1000 grains. L'évapotranspiration saisonnière (ET) était inférieure de 4 à 23%, la productivité de l'eau (WP) était plus élevée de 18 à 57% et la productivité de l'eau d'irrigation (PTI) a été supérieure de 21 à 81% dans le cas de l'irrigation par aspersion. L'analyse statistique des données des quatre années en utilisant le modèle linéaire généralisé a montré que la méthode d'irrigation par aspersion a augmenté de façon significative le rendement des cultures, WP et IWP, ainsi qu'une diminuation significative d'évaporation des cultures. WP et IWP ont également été significativement affectés par les conditions climatiques et les pratiques agronomiques. Par conséquent, la méthode de l'irrigation par aspersion a été recommandée comme une méthode d'irrigation efficace et d'économie d'eau pour les cultivars de blé d'hiver dans la plaine de Chine du Nord.

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Measurements of porosity and pore size distribution provide important data on the physical properties of soils. This paper presents a digital image method for the analysis of soil pores. In the analysis of soil thin sections, the image threshold separating pore space from the surrounding solid, as well as the capillary pore size threshold separating air pores and capillary pores, was obtained by analysis of the thin sections of calibration samples where values of total porosity and capillary porosity were predetermined by traditional soil physics methods (IM). The total porosity and capillary porosity, as well as percentages of pores of a particular size, of all samples of similar soil type can then be determined by these image thresholds in thin section image analysis. The maximum capillary pore size in soils can also be determined. Because the thresholds for the total porosity and capillary porosity are determined based on physical soil characteristics in this method, the error associated with existing methods (caused by subjective threshold estimates) was overcome. Small variations in results proved that this method has good accuracy and is acceptable. Any personal computer and flatbed scanner, along with any commercial remote sensing software (ENVI, PCI, ERDAS, etc.) and Geographic Information System software (ArcGIS, ArcView, SuperMap, etc.) are sufficient to complete the method. In addition, the method can also be used for analysis of pore shapes and arrangements.