Potato No-Till Broadcast Placement and Mulch Cultivation Technique

Saving labor costs of 150 yuan/mu, increasing production efficiency by 37.6%

Potato no-till broadcast placement and mulch cultivation is worth promoting

No-till broadcast placement with full-season rice straw mulching is a brand-new complete potato planting technique today. It refers to opening furrows and dividing beds according to certain specifications on unplowed land, applying basal fertilizer in strips on the bed surface, placing seed potatoes at a certain density in the fertilizer-free zone between two rows of fertilizer, and then covering the whole period with rice straw. Because this method is simple to operate, saves labor and effort, and also allows potatoes to be picked in batches and sold according to price, it improves planting efficiency and has aroused great interest among farmers and agricultural science and technology workers. At the beginning of last year, Ningxiang County, Hunan Province introduced this technique. Surveys showed that using this technique to plant 1 mu of potatoes required 7.5 labor units, with labor costs of 150 yuan, respectively 46.4% and 38.9% less than the traditional method (plowing and preparing land, then digging holes and sowing, covering with fine soil); soil available nitrogen, phosphorus, and potassium increased by 18.4 mg/kg, 4.9 mg/kg, and 11.8 mg/kg respectively compared with the traditional method; organic matter increased by 14.2%; and production efficiency per mu increased by 37.6%. Therefore, the area where this practical technique is promoted has expanded year by year. However, at present, in large-area practical application, this technique still has some difficulties or restricting factors, such as shortage of straw sources, delayed and uneven emergence, and so on.

1. Analysis of Restricting Factors

1. Insufficient rice straw resources: Using no-till broadcast placement with rice straw mulching technology, calculated at the standard rice straw mulching thickness of 8-10 cm, planting 1 mu of potatoes generally requires the rice straw from 3 mu of paddy fields. Small-scale scattered planting will not encounter much difficulty, but contiguous large-area planting becomes a problem, and if the rice straw is not near the potato planting field, gathering this rice straw together is also not easy. With the expansion of mechanized harvesting area, rice straw resources are becoming increasingly scarce.

2. Slow and uneven emergence: In 2002-2003, comparative trials of no-till broadcast placement with rice straw mulching planting and the traditional method were carried out respectively at the base of the Ningxiang County Agricultural Technology Center and at Tangsi Village, Meitanba Town: the varieties used were Dongnong 303 and Atlantic. Dongnong 303 was sown on January 3 and emerged on February 25. Compared with the traditional method, the emergence stage was delayed by 7 days, the emergence peak was on March 6, delayed by 10 days, the end of emergence was March 15, delayed by 15 days, and the emergence duration was 18 days, extended by 8 days; the emergence situation of Atlantic showed a similar trend to Dongnong 303, with the emergence stage on February 21, delayed by 6 days compared with the traditional method, the emergence peak delayed by 9 days, and the emergence duration 19 days, extended by 8 days. Large-area demonstrations also showed basically the same characteristics. The reasons for this phenomenon are: first, after sowing, the soil moisture on the bed surface was insufficient, and together with the dry rice straw, it was difficult for the seed potatoes to absorb water, delaying emergence. Second, the rice straw mulch was too thick or pressed too tightly, hindering the upward growth of seedlings, causing some potato seedlings to grow horizontally within the rice straw layer and become "blanched seedlings." In addition, if the rice straw mulch was too thin, its frost-prevention and sun-protection effects were small and ineffective, also affecting emergence.

3. High rate of green potatoes: In 2003, a survey of 118 farmer households at potato no-till broadcast placement demonstration bases such as Meitanba Town found that 25 households had relatively serious green potato occurrence, with the green potato rate reaching 7%-12.5%, averaging 8.6%. In comparative trials conducted in 2003 and 2004, the green potato rates using no-till broadcast placement with rice straw mulching technology were 4.84% and 3.26% in the two years, respectively 4.1% and 2.6% higher than the traditional method. The reasons are: first, the rice straw mulch was too thin. Second, the joints where the mulching rice straw met were not tightly connected. Third, strong winds blew away or moved the mulching rice straw. Fourth, damage by animals such as chickens, ducks, and dogs. Fifth, rotting of the rice straw mulch in the later period. These reasons can all cause incomplete rice straw mulching and light leakage, causing potato tubers to receive light and form green potatoes.

2. Corresponding Countermeasures

1. Develop alternative mulch resources: In production practice, farmers have used blighted grain, rice husks, sawdust, as well as leaves and weeds, etc. as potato mulch and achieved relatively good results. In order to screen out good mulches and find new mulches, relevant trials were conducted in the spring of 2004. The trial was conducted in Jinnan Village, Lijingpu Town, with 4 treatments: traditional method (as CK), rice straw mulching, rice husk mulching, and weed mulching. Sowing was on January 5. The emergence stages were as follows: rice straw mulching February 20, rice husk mulching February 17, weed mulching February 21. They were respectively 8 days, 5 days, and 9 days later than CK. The emergence durations for rice straw mulching, rice husk mulching, and weed mulching were 16 days, 11 days, and 18 days respectively, 7 days, 2 days, and 9 days longer than CK respectively. Yield was highest with rice husk mulching, at 1.67 tons/mu, 29.8% higher than CK; rice straw mulching was second, at 1.41 tons/mu, 8.9% higher than CK. Comprehensive analysis showed that rice husk was the best mulch, rice straw second, and weeds third.

2. Improve mulching quality: First, ensure the mulching thickness. Generally, after laying down the mulch without pressing it tight or lifting it loose, 8-10 cm is appropriate. In 2004, trials were conducted successively on three mulches - rice straw mulching, rice husk mulching, and weed mulching - at three mulching thicknesses of 3 cm, 6 cm, and 9 cm. The results showed that the green potato rates under the three mulching thicknesses for rice husk mulching were 30.2%, 8.3%, and 4.9%; for rice straw mulching, the green potato rates under the three mulching thicknesses were 27.8%, 12.7%, and 6.4%; for weed mulching, the green potato rates under the three mulching thicknesses were 33.2%, 15.8%, and 8.5%. This shows that appropriately increasing mulch thickness can effectively reduce the green potato rate. Of course, thicker is not always better, otherwise it will affect emergence. Second, pay attention to the mulching method. When using rice straw or weeds as mulch, place the tips of the straw or weeds toward the middle of the bed and the bases toward the edges of the bed, first covering both sides of the bed, then the middle of the bed. First spread coarsely, then fill in solidly.

3. Strengthen field management: Field management after sowing mainly focuses on the five tasks of "water control, seedling guiding, topdressing, spraying, and patching leaks." "Water control" means that after sowing, moisture on the bed surface must be well controlled, requiring the bed surface to remain moist and preventing too much or too little water. If the bed surface is dry and no rain is expected in the near future, then after sowing, fill the furrows with water up to the bed surface, then let it drain naturally, so that the bed soil becomes moist and emergence is promoted. If the bed surface is too wet at sowing or there is continuous rainy weather for a long time after sowing, then clear the furrows and drain water to prevent tuber rot. "Seedling guiding" means that during the emergence stage, for seed potatoes whose seedlings have not exposed the mulch, gently push aside the mulch at the seed potato to guide out the seedling, then restore the mulch. This speeds up emergence, advances emergence time, and prolongs the vegetative growth period. "Topdressing" means that after full emergence, apply a seedling-strengthening fertilizer once, generally applying 5-8 kg of urea per hectare mixed with 500 kg of water, to promote early and rapid plant growth and enhance the covering and shading effect on the bed surface. "Spraying" means using agents such as carbendazim in the middle and late growth stages to control diseases such as late blight, preventing leaf loss and seedling withering that affect yield and quality. "Patching leaks" means frequently inspecting the field and, where the mulch has shifted and leaked light, promptly restoring it or adding mulch to prevent the occurrence of green potatoes.

4. Improve sowing and mulching techniques: Appropriately increase sowing density. Generally speaking, sowing density can be increased by about 10% compared with the traditional method. For example, if Dongnong 303 is sown at 4000 hills per mu under the traditional method, then with no-till broadcast placement with rice straw mulching technology about 4400 hills per mu can be sown. In this way, on the one hand, the covering area and coverage degree of the bed surface can be increased; on the other hand, the yield of early potatoes can be increased, which is favorable for seizing business opportunities, increasing potato picking, bringing to market early, and increasing benefits.