When to Plant Corn in Northern China? A Detailed Guide to Planting Methods
The northern spring-planted corn region generally includes all of Heilongjiang, Jilin, Liaoning, Ningxia and Inner Mongolia, most of Shanxi, and parts of Hebei, Shaanxi and Gansu, and is one of China's main corn-producing regions. It accounts for 39.2% of the national corn area and 43.8% of the national total output. Its planting time is generally in spring.
The northern spring-planted corn region belongs to the cold temperate humid and semi-humid climate zone, with low temperatures and dry conditions in winter and a frost-free period of 130-170 days. Annual precipitation is 400-800 mm, of which 60% is concentrated in July-September. The Northeast Plain has flat terrain, fertile soil, suitable temperatures in most areas and ample sunshine, making it suitable for growing corn; it is China's main corn-producing region and an important commercial grain base. Corn is mainly grown on dry land, and the area of corn with irrigation conditions is less than one fifth. Corn yields in this region are very high, averaging about 6 tonnes per hectare. The highest yield reaches 15 tonnes per hectare.
1. Cropping system
The northern spring-planted corn region is basically a one-crop-per-year system. There are three types of planting methods:
(1) Sole cropping of corn. This accounts for more than about 50% of the corn area and is distributed across the plains of the three northeastern provinces and the high-cold areas of northern Inner Mongolia, Shaanxi, Gansu, Shanxi and Hebei. Because the frost-free period is short and temperatures are relatively low, corn is grown as a single-season crop, but corn plays an important role in crop rotation, usually rotating with spring wheat, sorghum, millet, soybean and other crops. This situation changed greatly after the 1970s; because the corn sown area increased rapidly, rotation and stubble switching became very difficult, so it developed into a continuous corn cropping system.
(2) Corn-soybean intercropping. This accounts for about 40% of the area in this region and is the main form of corn planting in the Northeast. Corn-soybean intercropping makes full use of the morphological and physiological differences between the two crops and combines them rationally, improving the utilisation rate of light energy, water, soil and air resources. Corn-soybean intercropping can generally increase grain and bean yields by about 20%.
(3) Spring wheat interplanted with corn. After the 1970s, in northern Shaanxi, northern Shanxi and parts of Liaoning, Gansu and Inner Mongolia with better water and fertiliser conditions, the planting method of interplanting corn in spring wheat gradually took shape. It mainly adopts the method of sowing wheat in wide beds and interplanting or transplanting spring corn seedlings on the bed ridges, and can generally increase yields by 20-30%.
2. Main corn varieties planted
The northern spring-planted corn region actually includes two areas: the Northeast and North China. The Northeast needs varieties with a moderate or relatively early maturity period, tolerance to low temperatures and good yielding ability. There is basically no epidemic of viral disease or southern leaf blight in the Northeast, but there is northern leaf blight and head smut, and sometimes corn borer damage occurs, so resistance to these diseases and pests is required. According to statistics, the main corn hybrids planted in the Northeast include Benyu 9, Jidan 159, Sidan 19, Zhongdan 2, Yedan 19, Danyu 13, Yedan 13 and Shendan 7, etc.
Spring-planted corn in North China suffers severe damage from viral disease, and also from stalk rot and northern and southern leaf blight, so the requirements for varieties are stricter. The main cultivated varieties include: Yedan 13, Yedan 12, Yedan 19, Xiyu 3, Yedan 2, Zhongdan 2 and Yandan 14, etc.
3. Analysis of production conditions
The favourable conditions for developing corn production in the northern spring-planted region are: flat terrain, deep soil layers, fertile soil and relatively abundant light and heat resources. The region's agricultural production level is relatively high, corn yield increase potential is great, and it has the advantage of commercial production.
The main factors limiting corn yield increases in this region can be summarised in five points: first, production areas are concentrated and circulation is poor, so storage, transport, processing and sales after corn harvest are all very difficult; second, autumn frost comes early, temperatures are low, grain dehydration is slow, which lowers quality grades and increases energy consumption; third, drought and little rain, and insufficient irrigation facilities and water resources; fourth, low inputs, especially insufficient fertiliser, with an unreasonable nitrogen-phosphorus-potassium ratio; fifth, a lack of new varieties with stable and high yields. To further develop corn production in this region, the strategy should be to stabilise the area and increase yields.
4. Measures to further increase yields
(1) Replace with new varieties. There is an urgent need to breed or introduce new hybrids that are early-maturing, high-yielding, lodging-resistant, suitable for dense planting and mechanised operations. Excellent new varieties are needed that dehydrate quickly in the late grain-filling stage and have good quality, resistance to head smut and northern leaf blight, tolerance to gray leaf spot and resistance to corn borer.
(2) Increase inputs. The amount of chemical fertiliser applied in this region is far from the nitrogen, phosphorus and potassium requirements for corn yields of 1,000 jin per mu. If fertiliser inputs are not increased, long-term continuous corn cropping will severely damage soil fertility and cause the agricultural system to lose sustainability. If balanced fertilisation according to local conditions can be achieved, yields will increase considerably.
(3) Expand the area under plastic film mulching. The corn plastic film mulching area in Heilongjiang Province has already reached 3 million mu, and factory seedling cultivation and new mechanised transplanting technologies are currently being tested; this is one of the powerful measures for greatly increasing yields. Parts of Shanxi, Inner Mongolia, Liaoning and Jilin are also suitable for developing corn plastic film mulching technology.
(4) Reform the grain circulation system and expand circulation channels, while also increasing drying machinery and storage and processing facilities. When variety moisture content is high, drying machinery should be installed to speed up grain dehydration after corn harvest, properly solve the problems of safe grain storage, transport and circulation, improve quality grades and expand export capacity. Attention should also be paid to the development of post-harvest processing industries, protecting farmers' enthusiasm for growing grain through multiple channels and stabilising production.