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Grasslands and Grassland Sciences in Northern China
The Grassland Agricultural System developed at GGERI's Jingtai [County] Experimental Station produced similar results. He and Ge (1990) have shown that in this case, when corn was intercropped with beans and sweet clover, the production of grain, crude protein, and energy—and the economy as a whole—increased significantly in comparison to areas devoted to monoculture. In addition, the occurrence of crop diseases was drastically reduced (Ge Wenhua, personal communication).
As described by Ren and Shen (1990), the Grassland Agricultural System has four production levels: preprimary production (recreation, soil conservation); primary production (crops, forage, medicinal herbs); secondary production (animals and animal products); and postsecondary production (processing and commodity circulation). Organized in this way, the agrosystem can operate more efficiently, while causing less environmental damage. Forage plants play a key role in this system by preventing soil erosion and enriching the soil. Agricultural by-products, which represent 75% of the plant matter not directly consumed by people, can be converted to animal products. Animal manure is used to improve soil fertility. Unlike traditional agriculture in which the farming season ends with the last harvest, in the Grassland Agricultural System, forage production begins before planting and continues after the harvest.
RECLAMATION OF SALINIZED LANDS
Establishment of the Grassland Agricultural System has been accompanied by reclamation of salinized agricultural lands, which can be reseeded in grass. In the past, reclamation of saline land relied on an engineering approach, which has been found to be too expensive. With the help of Wu Qingnian of the Jilin Academy of Agricultural Sciences, a group of researchers introduced to the Hexi Corridor several salt-tolerant perennial species of the genus Puccinellia, most notably P. chinampoensis.
Several years of field trials have shown that Puccinellia is well adapted in slightly to medium-saline soil and can survive in heavily saline soil in some circumstances. The salt dynamics of the saline land and the ecophysiology of Puccinellia and other salt-tolerant species (Phragmites communis, Agropyron cristatum, Achnatherum splendens, Calamagrostis epigojos, and Hordeum brevisubulatum) have been studied and the results reported in a special issue of Pratacultural Science of China (1988). The findings of this project include the following: (1) Under field conditions, Puccinellia can tolerate a salinity of 2.4% in a 45-or 60-cm soil profile. (2) Puccinellia seedlings are less tolerant of high salt content; therefore irrigation must be applied at an early growing stage. (3) Puccinellia can desalinize salt-affected land in two to three years, bringing salinity down from 2–3% to 0.2–0.4% in a 30-cm soil profile. (4) After the establishment of Puccinellia, there is little seasonal or annual fluctuation of soil salinity (Zhu et al., 1988). (5) Three years after Puccinellia was established,