Intercropping Coix with Safflower: Cyclic Improvement of Wetland Soil and Water

I. Brief Introduction

1. The significance of wetland soil and water improvement

With China's modernization, the rapid development of agricultural industrialization and industrialization, and the reform of agricultural planting systems, environmental pollution has become a bottleneck for social development: air pollution, soil pollution, water pollution, and so on; the increase of carbon dioxide, sulfur oxide and other gases in the atmosphere and the relative decrease of oxygen; the residue of heavy metals such as lead, mercury and cadmium in the soil; and the pollution of harmful elements in freshwater bodies. How to carry out scientific, rational, safe, effective and naturally cycling treatment, so as to maintain economic development and ensure ecological balance, is the primary task of every one of us citizens. We should plan for the long term, think of the next generation, share the nation's concerns and benefit the people.

2. The role of intercropping safflower with Coix in the cyclic improvement of soil and water

Safflower is an annual herbaceous plant of the Asteraceae family, with a plant height of 80--120 cm and an upright stem. It prefers a warm climate, is relatively drought-tolerant and cold-tolerant, and has strong adaptability. In Shandong and other Huang-Huai regions, it is sown in autumn and harvested in early summer, and is a half-year xerophytic plant. Coix, however, is exactly the opposite of safflower in growth habits: it not only prefers moist soil but can also tolerate living in water for a certain period of time, and it fears drought and water shortage most of all. Its vigorous growth period is in June, after the safflower harvest. Therefore, intercropping safflower with Coix is early in one case and late in the other in terms of growth time, which exactly suits the climatic patterns of Shandong; in terms of growth habits, one is drought-loving and the other flood-tolerant, which completely matches the seasonal alternation of flooding and drying in lake-beach wetlands. In this way, an artificial wetland treatment ecosystem is established, creating a relatively reasonable and practical cyclic improvement technical model for large-scale environmental soil and water treatment of wetlands.

3. Considerable economic benefits

Through the intercropping of safflower and Coix, the environmental conditions in the wetland soil and water can be effectively and cyclically improved. At the same time, the xerophytic safflower and the hygrophytic Coix fully absorb the effective elements in the soil, thus growing vigorously and robustly, enabling the wetland soil to achieve its maximum productive capacity, with two harvests a year and significant economic benefits. Based on general yields, the benefits generated in one year are calculated as follows: per mu (667 sq m), 20 kg of safflower commodity can be harvested, at a market price of 40 yuan/kg, totaling 800 yuan; 100 kg of safflower seed, at a market price of 2 yuan/kg, totaling 200 yuan; 300 kg of shelled Coix, at a market price of 4 yuan/kg, totaling 1200 yuan; the total annual income per mu can reach 2200 yuan.

II. Brief Introduction and Biological Characteristics of Safflower and Coix

1. Safflower, also known as grass safflower, is an annual herbaceous plant of the Asteraceae family. Its flowers are used medicinally and have the functions of activating blood and promoting menstruation, removing blood stasis and relieving pain. It is mainly used to treat coronary heart disease, angina pectoris, dysmenorrhea, and so on, and is an important gynecological medicine. Safflower seed has a relatively high oil content of 20-30%, and is the main raw material for the currently rather expensive health-care edible safflower oil. At present, the variety planted in Shandong is the short-spined safflower, which has strong adaptability. Because its root system is well developed, it can absorb water and nutrients from deep soil layers to meet its own growth needs, so it is relatively tolerant of poor and dry conditions. Its flowering period is in May, and the seeds mature in early June.

2. Coix is a hygrophytic or swamp-dwelling annual grass family plant, and is not drought-tolerant. It is currently divided into three varieties: early-maturing, mid-maturing and late-maturing. Generally, early-maturing varieties are suitable for planting in the northwestern region, while late-maturing varieties are suitable for planting in the south, south of the Yangtze River. The mid-maturing varieties are most suitable for the central Huang-Huai regions such as Shandong. The above classification is based on their characteristics. In Shandong, Coix is generally sown in May when the ground temperature stabilizes above 20°C. The seedling stage is 40 days, stem elongation (jointing) is 16 days, booting is 8 days, and the grain-filling period is 60 days, with a total growth period of about 124 days. Especially in the middle and late growth stages, it can relatively strongly tolerate the salt damage and moisture brought by swampy land. The water requirements throughout the growth period can be summarized as follows: (1) 40 days of moist seedling growth (2) 15 days of dry jointing (3) 8 days of booting with water (4) 60 days of sufficient water for heading and grain filling (5) dry field for harvest and processing. Therefore, Coix has a high water requirement throughout its life, and at the very least maintaining soil moisture is key.

III. Specific Operating Procedures

1. Safflower sowing: In autumn, from September to October, wait until the surface soil in the wetland is slightly dry and can be cultivated, then apply 50 kg of organic fertilizer per mu as base fertilizer. After plowing, turning and raking evenly (if the soil is relatively wet, plowing and turning may be omitted), sow safflower in wide and narrow rows, with a wide-row spacing of 50 cm and a narrow-row spacing of 30 cm, using 3 kg of seed per mu. Basically no management is needed during the growth period, except that around the Awakening of Insects solar term, chemical control techniques are used to control its growth height or prevent lodging in the later stage.

2. Intercropping Coix: From early April to early May, when flower buds appear on the safflower, select mid-maturing Coix varieties with thin shells and a high milling yield. In order to prevent the harm of smut disease occurring on a large scale in Coix, the seeds must be treated before sowing. The treatment method is: choose a sunny day and sun-dry the seeds for 1-2 days, then soak them in water for 24 hours, remove and drain the water, and dress the seeds with 0.4% triadimefon. After seed treatment, sow one row of Coix in the wide rows of safflower, using 5 kg of seed per mu. From mid-to-late May to early June, after the safflower and its seeds are harvested, this is also when the annual plum rain season begins. The water level in the tidal-flat wetland rises, providing favorable conditions for the growth of the hygrophytic or aquatic Coix, and basically no management is needed. It can be harvested in September--October.

IV. Comprehensive Social Benefits of the Intercropping Model

Because tidal-flat wetlands must go through a flooding period and a drying period each year, and these have obvious seasonality. According to scientific research and analysis, during the flooding period, general wetlands have much stronger denitrification than dry land, so the nitrogen content is relatively low; while the content of available phosphorus increases, because after soil flooding, the pH rises, which can promote the hydrolysis of iron phosphate and aluminum phosphate, transforming occluded phosphorus into non-occluded phosphorus, and the availability of phosphorus is somewhat improved. Therefore, under the alternating conditions of flooding and drying, the content of available phosphorus increases during the flooding period. The contents of other trace elements such as boron and iron decrease during the flooding period, while manganese and copper increase. Based on the above analysis of wetland soil nutrients, and combined with the growth habits of safflower and Coix, the environmental conditions of the wetland after drying are exactly the full growth period of safflower, while the season prone to flooding is exactly the vigorous growth period of Coix. Safflower and Coix are deep-rooted crops, and their massive root systems can penetrate 50 cm into the soil, with most distributed within 30 cm of the surface soil layer around the plants. Therefore, after the wetland dries, the safflower root system absorbs excess elements such as nitrogen and phosphorus that accumulated in the soil during the previous year's flooding period, to satisfy its own growth needs. At the same time, through the absorption and utilization of organic or inorganic substances in the soil, it reduces the soil pollution caused by heavy metals formed from these excess elements, improves the soil, and prevents the wetland soil from causing secondary pollution to water quality after rainwater or rising water levels, ensuring the purity of the water. After June, when the safflower has been fully harvested and Coix enters its vigorous growth period, this is also the critical period when water quality is most easily polluted. During this period, various aquatic organisms reproduce in large numbers. If the content of organic matter in the water can be reduced, the growth and reproduction of various aquatic organisms can be effectively inhibited. In this period, in ordinary years, it is also the period with the most rainfall, and the wetland may accumulate water in a short time and become shallow-water flats. This period is also the peak water-demand period for Coix. As long as water does not accumulate for a long time, Coix will grow vigorously. Soluble organic matter in the water body is adsorbed, absorbed and decomposed and removed through the biofilm of the Coix root system and biological metabolism, and harmful substances such as cyanide and phosphorus can be effectively removed, thereby purifying water quality and reducing pollution of the water body.