Li Xiujun

Sustainable agriculture development in saline-alkali soil area of Songnen Plain, Northeast China

There is great potential for agriculture in saline-alkali soil area in Songnen Plain, Northeast China. But the sustainable crop production in this area has been restricted by a few of main factors, such as less precipitation, higher evaporation and frequent drought, high salinity and alkalinity, high exchangeable sodium content and poor infiltration of the soil, and insufficiency and low availability in nutrition. It is also considered that there are a few of favorable conditions for agricultural development in this region, such as sufficient light and heat resources, rich ground water resources, plenty of manure produced by livestock, and so on. At the same time, scientific management and measurements have been employed; rational irrigation and drainage system has been established; reclamation, amendment and fertilization of soil, and suitable strategies of cropping practices have been made for the sustainable development of agriculture. Great progress has been made during 1996 – 2000.

Characteristics of Channeling Flow in Cultivated Horizon of Saline Rice Soil

By applying bromide ion as tracer, the channeling flow has been quantitatively described in saline rice soil and alkaline soil of Da’an City, Jilin Province of China. Breakthrough curves of bromide ion in the saline rice soils after 1-year cultivation and 5-year cultivation and alkaline soil have been attained. Results show that the rice cultivation practice can improve the alkaline soil structure, however, it can accelerate the development of channeling flow pathway. Therefore, the channeling flow pathway has been developed widely in saline rice soil, but rarely in the alkaline soil. Three models of convection-dispersion equation (CDE), transfer functional model (TFM) and Back-Progation Network (BP Network) were used to simulate the transportation process of bromide ion. The peaks of probability density function of saline rice soil are higher with left skewed feature compared with that of the alkaline soil. It shows that the TFM and CDE can simulate the transportation process of the bromide ion in saline rice soil after 5-year cultivation, however, some deviation exists when it was used to simulate transportation process of bromide ion in saline rice soil after 1-year cultivation and alkaline soil; BP network can effectively simulate transportation process of bromide ion in both saline rice soil and alkaline soil.

Spatio-temporal variations of soil respiration in five typical plant communities in the meadow steppe of the western Songnen Plain, China

Aims Soil respiration plays a critical role in the process of carbon cycling in terrestrial ecosystems, and it often shows spatio-temporal variations in response to diverse abiotic and biotic factors. Our objective was to examine the seasonal and spatial variations of soil respiration under five typical plant communities in the meadow steppe of western Songnen Plain. Methods Using a LI-6400 soil CO2 flux system, we investigated soil respiration and environmental factors under five vegetation types(Suaeda glauca, Chloris virgata, Puccinellia distans, Phragmites australis and Leymus chinensis) in the meadow steppe of Songnen Plain during the growing seasons of 2011 and 2012. Important findings Soil temperature was the dominant controlling factor of soil respiration, which explained approximately 64% of the changes in soil CO2 effluxes. Soil water content was not the limiting factor of the seasonal variations in soil respiration. The sensitivities of soil respiration to temperature(Q10) ranged from 2.0 to 6.7, showing significant differences among vegetation types. The cumulative CO2 emission averaged 316.6 g C·m–2 during the growing season. The magnitude of soil CO2 emission during the growing season was positively correlated with aboveground plant biomass, soil organic carbon content, and mean soil water content, and negatively linked to mean soil temperature, pH, electrical conductivity, and percentage of exchangeable sodium. The spatial variations of soil CO2 emission were mainly caused by changes in soil microclimate, plant biomass, and soil properties.

IMPROVEMENT OF SANDY SOIL WITH WATER-CONSERVING MEMBRANE AND ITS EFFECT ON CROP GROWTH

Water-conserving membrane is a new material of improving sandy soil. It is based on the rule that a compound with organic and inorganic components can produce colloid after its integrating with Ca2+ in soil. The water-conserving membrane will obstruct capillary and increase viscidity of sandy soil, so as to decrease leakage and evaporation in sandy soil. The water-conserving membrane contains polyacrylic acid (PAA) and bentonite. When PAA concentration and pH of solution are different, water-conserving membrane can be made in different depth of soil. This experiment shows that the solution with 0.2% PAA does not harm and poison the crops, on the contrary, promotes crop germination. The solution with 0.2% or 0.4% PAA can accelerate corn growth. Accordingly, different crops need the application of the different PAA concentrations in the cultivation. Therefore, on the basis of different vadose coefficient in sandy soil, the solution with different PAA concentration can improve sandy soil and increase its water-conserving competence very well. The solution can be used to improve sandy soil and control desert enlargement in arid, semi-arid and semi-humid areas.