Establishment Of Potato-Including Double Cropping System At Hetao Irrigated Area And The Evaluation Of Its Resources Use Efficiencies

Hetao irrigated area of Inner Mongolia has the convenient irrigation. And the long-term flooding irrigation and autumn irrigation adding the excess usage of nitrogen fertilizer, which lead to the local groundwater’s nitrate contamination seriously. The excess usage of water and fertilizer at Hetao irrigated area of Inner Mongolia can not be easily altered in the short time because of the Yellow River water distribution. Potato is the fast developing crop at this place. However, the water and nitrogen fertilizer’s use efficiencies in the local potato production are even lower because of potato’s shallow root system. For ensuring the sustainable development of potato industry, immediate solution is required to improve the resources use efficiencies of potato without changing the flooding irrigation pattern. Hetao irrigated area had abundant solar energy, and long frost-free season, therefore, this research proposed a hypothesis of shallow root crop(potato)+deep root crop culture pattern to improve resources use efficiencies, that was to change mono potato production into double cropping system. An early potato+cover crop double cropping system was established at Hetao irrigated area of Inner Mongolia through the combinational technology applications including plastic mulch, early potato culture, deep root crop culture, selection of the cover crop, and nutrient management to improve the resources use efficiencies, net economic returns and alleviate the nitrate contamination in groundwater. The results were as follows:1. The apparent nitrogen recovery ratios, solar energy use efficiencies, land equivalent ratios, net economic returns of the early potato+deep root crop double cropping systems were significantly higher as compared to those of the conventional late potato mono cropping system. The nitrate residual contents within0-160cm soil profile of the early potato+deep root crop double cropping systems were markedly lower than that of the conventional late potato mono cropping system. For the multiple purposes including reducing soil nitrate leaching risk, improving apparent nitrogen recovery ratio, improving solar energy use efficiency, improving land equivalent ratio, improving net economic return, the early potato+cabbage double cropping system (DCS) was the ideal choice compared with early potato+sunflower DCS, or early potato+sorghum hybrid sudangrass DCS.2. At the nitrogen fertilizer applied rate of225kg N/hm2with50%basal application+50%top dressing, the potato agronomic traits, dry matter accumulations of different organs were significantly improved compared with those of the same nitrogen fertilizer applied rate with100%basal application for different potato cultivars. Therefore, the potato yields, net economic returns, apparent nitrogen recovery ratios, and water use efficiencies were remarkably improved. The nitrate residual contents within0-160cm soil profile after late potato harvest treated with50%basal application+50%top dressing were markedly lower than those of100%basal application at the nitrogen fertilizer applied rate of225kg N/hm.3. The10cm soil temperature,0-20cm soil moisture were significantly improved by plastic mulch. The plastic mulch treatment reduced the risk of nitrate leaching to deeper soil, and improved the water use efficiencies of potatoes. The plastic mulch treatment improved the early potato development process, dry matter accumulation, fertilizer partial factor productivity, solar energy use efficiency, tuber yield per plant, and total tuber yield. Though the dry matter accumulation was improved before late potato bulking stage compared to culture in the open, the plastic mulch treatment had no significant effects on fertilizer partial factor productivity, solar energy use efficiency, and total tuber yield of late potato. And the late potato tuber commodity rate was reduced by plastic mulch.4. Four level nitrogen fertilizer rates’effects at after crop were tested within early potato+cabbage double cropping system, and the results showed that:the cabbage yield, the system net economic return were the highest at the nitrogen applied rate of120kg N/hm2. With the nitrogen applied rates increasing, the system solar energy use efficiency, cabbage water use efficiency were significantly improved, but the apparent nitrogen recovery ratio was reduced. Nitrate contents in cabbage and nitrate residual contents within0-160cm soil profile were significantly increased with nitrogen fertilizer increasing at after crop. It was impossible to coordinate between cabbage yield, net economic return, and nitrate contents in cabbage, soil nitrate residual content.5. Sorghum hybrid sudangrass (SHS) planting density effect was tested at the nitrogen fertilizer rate of225kg N/hm2, and the results indicated that:in the planting density range of80000-250000plants/hm2, the SHS fresh yield, dry yield, water use efficiency, DCD apparent nitrogen recovery ratio, DCD solar energy use efficiency, were significantly improved with the SHS planting density increasing. The nitrate residuals within0-160cm soil profile after SHS harvest were remarkably reduced with the SHS planting density increasing, therefore reduced the ground water nitrate contamination risk. 6. The early potato Favorite cultured with plastic mulch at Hetao irrigated area showed that with the extension of growth period, nitrogen, phosphorus, and potassium concentrations at different organs dropped. The total nitrogen, phosphorus, and potassium accumulations in root, stem and leaf showed a unimodal curve, while the nitrogen, phosphorus and potassium in tuber increase with the extension of growth period. To produce1000kg potato tuber with plastic mulch at Hetao irrigated area, the early potato Favorite required N:3.00kg, P2O5:1.53kg, K2O:6.72kg, respectively. The recommended nitrogen fertilizer applied rate for late potato Kexin No.1mono cultured in the open at Hetao irrigated area was190kg N/hm2.