Rice-rice-potato rotation system Potato likes to grow in the cool environment. The suitable temperature for potato development ranges from 15-18 0 C.If temperature is higher than 25 0 C, potato growth slows down and even stops. Only if temperature drops down below zero, potato plant would face freezing damage. Temperature during winter period in south subtropical and northern tropical region is suitable to grow potato. Rice rice potato rotation system not only can make good use of seasonal resources for more food production. The use of rice straw as field cover in no-tillage potato or as basal fertilizer in tillage potato can increase the recycling rate of rice straw to gain more plant nutrient supply and soil organic matter supply. 3.1 Technique used for rice-rice-potato system Seed potato preparation: The loam soil or sandy soil with good irrigation system is suitable for rice rice potato system. Potato variety used should be adapt to the specific local climate and soil condition. Early maturing and mid-maturing varieties are preferred. The major varieties used in South China include Favorita, Pacific, Cadinal, Zhongshu No. 3, and Hezuo No.88 etc. Detoxified seed potato which is free of virus disease pathogen, is important for high yield. The seed potato can be cut into pieces with 1 to 2 buds each. The seed potato pieces can be further disinfected and then incubated for germination. Seed potato pieces are incubated within moist sand bad. It is suitable to have 10 cm sand below potato and 10 cm sand above potato. The moisture content of sand should keep at 60%. When the buds emerge and reach about 1-2 cm, they are ready to be planted in field. Planting: After the harvest of second rice crop in fall, potato can be planted in field. For no tillage potato, a ditch system should be dig out to facilitate drainage and irrigation. Ditch around the field and straight ditches about 1.6-1.8 meter apart within the field are necessary. Ditch is 20-30 cm width and 15-20 cm depth. Then the seed potato pieces can be put on the field surface with row space 30-40 cm and space within row 20-30 cm. Rice straw with 8 10 cm thick is used to cover the seed potato. The amount of rice straw used is straw from 1 2 ha rice for 1 ha of no tillage potato. Enough amount of straw cover is important to keep moisture, to keep dark environment for potato root system and to provide nutrient for potato from the straw decomposition. To put soil to partly cover the straw is needed to hold the straw in position. 1
Fig. 3.1 The layout of no-tillage potato field after the harvest of the second rice in early November in Guangxi Region, China (By Luo Shiming) For tillage potato, plough and harrowing after rice harvest is needed. A raised bed with 85-90 cm width and 20-25 cm high is prepared with a 20-25 cm ditch between beds. Before bed preparation, basal fertilizer should be put in the middle of the bed position. Then seed potato pieces are put on the bed with two rows and then covered with 5-6 cm soil. The density is 60 thousand to 75 thousand plants per hectare with row space 30 cm and space within row 25-30 cm. The buds of seed potato pieces should point upward. Rice straw can be put with the basal fertilizer together within the bed, or cover the bed after planting. Straw covering the bed should not be too thick to delay seedling emerging. The amount of straw use is 0.5 1 ha rice straw for 1 ha of tillage potato. If straw is put on the bed, covering some soil to press rice straw on position is needed. Fertilization: The nutrition need for production of potato can be calculated on the base of 5.5 kg of N, 2.2 kg of P 2 O 5 and11 kg of K 2 O for 1000 kg of potato. The yield of potato usually is in the range of 15 ton/ha to 37.5 ton/ha during winter season. This nutrition can be met by different types of organic fertilizer such as compost, farmyard manure, plant ash, slurry and liquid from biogas fermentation. Basal fertilizer should include 60% nitrogen, 100% phosphorous and 50% potassium needs for the whole season. The remaining fertilizer can be applied in 3 to 5 times according to the growth situation. Liquid form is 2
preferred for better absorption. Fig 3.2 The tillage potato in rice field in Huizhou, Guangdong Province, China (By Luo Shiming) Irrigation: The suitable soil moisture for potato growth ranges from 60 80 % of the maximum water holding capacity. For no tillage potato, a fast and quick irrigation method is recommended to avoid excessive standing water. For tillage potato, irrigation water should keep less than half full of the ditch. During rainy days, to maintain good drainage system for no-tillage potato is very important. Thinning: In case of more than 3 shoots come out from one seed potato, the redundant seedlings should be removed. Pest control: The most important methods of disease control include the use of detoxification seed potato, to avoid excessive nitrogen application, and good drainage during rainy season. Other pests can be controlled by integrated pest control methods. 3
Fig. 3.3 Before potato harvest in tillage potato field. It can be seen that rice straw together with rice straw within the raised bed (by Luo Shiming). Harvest: There is no special requirement for potato harvest for tillage potato. For no-tillage potato, it is very easy. Just take out the rice straw cover, potato will be exposed and is ready to be picking up. The half decomposed straw and the upper plant parts of potato can be remained in field as organic fertilizer for early rice production. 3.2 Typical cases and benefit analysis A farmer Xu Lianjin in Xinlu Village, Guigang, Guangxi Region rent 33.3 ha of winter fallow paddy field for no-tillage potato from the winter of 2010 to the spring of 2011. The average potato yield was 45 ton/ha. The highest yield reached 53.5 ton/ha. The price of potato was 2000 Yuan/ton. Total income per hectare was about 90,000 Yuan. The cost per hectare was about 30,000 Yuan. Net income per hectare reached about 60,000 Yuan. Total net income was more than one million Yuan. The rice field no-tillage potato in Guangxi Region reached 70 thousand hectare in 2011. It could reduce 20-30% of the cost and increased yield by 10 40% comparing to tillage potato. In the double rice region, Guangdong Province, the winter potato reached 5 thousand hectare in 2016. 4
Fig. 3.4 The farmers were harvesting no-tillage potato after rice straw was moved aside in Wuming County, Guangxi (from Zhao Chunxia, 2012) A potato experiment was conducted in Guangxi Region (He Xinmin et al., 2011) to compare with no-tillage potato covered with rice straw (NT), tillage potato with rice straw inside (TS), tillage potato with black plastic sheet cover (TB) and common tillage potato (CK). The result showed that the black plastic sheet cover could increase soil temperature and keep soil moisture, it had the highest yield. However, the rice straw used in no-tillage or tillage potato could also increase yield significantly. Considering the ability of recycling rice straw and increasing yield, the NT and TS method were recommended. Table 3.1 The comparison of different planting method for winter potato in Guangxi (He Xinmin et al., 2011) Treatment Yield Relative Cost (yuan/ha) Total Net Relative (kg/ha) yield (%) labor material income income net income (Yuan/ha) (Yuan/ha) (%) TS 28,401.3a 121.3 7320 5625 22721 9776 261.8 TB 28,977.5a 123.8 8654 5250 23182 9278 248.5 NT 25,247.9b 107.8 6510 5940 20198 7748 207.5 CK 23,406.2b 100.0 9291 5700 18725 3734 100.0 Reference He Xinmin, Tan Guanming, Tang Zhouping, He Huyi, Li Lishu, Wang Hui. Studies on Cultivation 5
Pattern of Straw Wrapping Potato in Winter Planting. China Vegetables. 2011 (2): 78-80. Wang Jianwu and Cai Kunzeng edited. Structure and Technique of Typical Circulation Agriculture in the field of the Pearl River Delta.2010. China Environmental Sciences Press. Beijing, China. Zhao Chunxia edited. Knowledge and Wisdom for Agricultural Development 10 year practice of innovative development of Guangxi agriculture. 2012. Hongqi Press. Beijing, China. Zhang Mingpei. The industry of tuber crops. 2011. Guangxi People s Press. Nanning, China. 6