| East part of Gansu province is the main food production area. It is essential to study the productive potential of main native crops as well as its key limiting factors for raising actual productivity, speeding rural economy development, and increasing income of farmers. Field experiment, designed in three-factor modle (the amount of fetilizer, planting density and cultivar) and combined with massive investigation of hi-yield field, was conducted to evaluate productive potential of the two dominant crops--winter wheat and corn in Longdong dryland. The main results show as follows.1. The changing range of some physiological indicators of winter wheat and corn under different fertilizer and density level. The water rate of mature winter wheat varied from 0.122% to 0.144%, the average was 0.131%. The ratio of respiration consumption to photoproduct varied from 0.5678 to 0.5513, the average was 0.5573. The revision index of leaf area showed a range from 0.7807 to 0.4826, the averge was 0.6278. To mature cron, the water rate appeared in a range from 0.154% to 0.167%, the average was 0.155%. Its ratio of respiration consumption to photoproduct changed from 0.4736 to 0.5324, the average was 0.4962. Its revision index of leaf area changed from 0.5910 to 0.5456, the average was 0.5687. The caculating results specified as above all changed in a small range, showing fertilizer and density affected little on all these physiological indicators.2. The response mechanism of winter wheat and corn to tempreture under different fertilizer and density level. The heat revision index(HRI) of winter wheat and corn varied with growth stage. The HRI of winter wheat ranged in order of heading stage>blooming stage>filling stage>jointing stage>rising stage>harversting stage> wintering stage>tillering stage>tri-leaf stage>seedling stage>turning stage, and that of corn was filling stage>mature stage>tasselling stage>jointing stage>seedling stage. The influnce caused by fetilizer and density on HRI of winter wheat and corn appeared to some extent, but not considerable. The monthly temperature revision index(TRI) of winter wheat and corn significantly varied(p<0.05), illistrating tempreture produced notible regulation and control on growth of winter wheat and corn.3. The influnce of fitilizer and desity on yield of winter wheat and cron. Amoung the treatments under different fitilizer and density level, the output markedly varied(p<0.05). The variation between"Longjian 301"and"IR17"reached to the most significant level ( p<0.01), and"Ningmai5"had significant difference (p<0.05) with"IR17". The output of"Longjian301", 4188.093 kg·hm-2 under applying net N 210 kg·hm-2 and sowing 4.2 millin kenels·hm-2,topped the list of all its designed treatments,"Ningmai5"showed the same tendency. The output of"IR17", 3018.18 kg·hm-2 under applying net N 105 kg·hm-2 and sowing 4.2 millin kenels·hm-2, took the highest of all its designed treatments. With the interaction amoung cultivars, fertilizer and density, the output of"Longjian301", 4188.093 kg·hm-2 under applying net N 210 kg/hm2 and sowing 4.2 millin kenels·hm-2, took the top and showed significant difference with other treatmens. The output of corn, 17089.66 kg·hm-2 under applying net N 180 kg·hm-2 and planting 67500 pill·hm-2, was significantly above (p<0.01) that of other treaments.4.The affection of fertilizer and density level on economic coefficient of winter wheat and corn under different fetilizer and densiry level. The changing range of economic coefficient of winter wheat and corn was from 0.290 to 0.531, the average was 0.372, and that of corn was from 0.4328 to 0.5812, the average was 0.8066. The econiomic coefficient of the two crops under difficient fertilizer and density level varied in a small range, indicating fertilizer and density had little regulation and control on ecobomic coefficient.5. The revision index of winter wheat and corn. The tempreture revision index, water rivision index and soil revision index of winter wheat were 0.5946, 0.3670 and 0.7267 respectively, and that of corn were 0.8018, 0.1520 and 0.7262 respectively. Considering natural ecological factors including light, tempreture, water amd soil, as well as faming technique factors covering fertilizing and cultivating methods, the revision of photosynthetic production potential was made step by step. The consequence showed that the maximum productive potential of winter wheat was 6757.44 kg·hm-2 respectively, and that of corn was 17089.66 kg·hm-2 respctively in East part of Gansu province.6. Ttempreture and rainfall were key impacting factors to the realization of crops'pertential produtivity in East area of Gansu. Tempreture and rainfall which are relatively vacancy in Longdodng region, are the main factors to decide whether crops can realize their productive potential or not. The water potential productivity index of winter wheat and corn were all not mare than 50%, so water was the main limiting factors for the native crops to realize their productive potential. In terms of cultivation measures, it is the most efficient hi-yield method to maintain soil water and improve its efficiency. Different crops have different capability to utilize resources. The heat potential productivity index of winter wheat was 0.69, and that of corn was 0.85, thus envolving that planting corn to a big scale in East part of Ganxu can make full of use natural resources and raise total food production.
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