Integrated double-cropping maize technology is mature, and the North China Plain can now grow it
On July 13, harvesting began on the 200-mu double-cropping maize demonstration plot in Lianzhu Village, Henan Tuan Town, Quzhou County, Hebei Province. “This is the earliest-harvested spring maize in Hebei Province and even in the North China region.” said Chen Xinping, a professor at the College of Resources and Environmental Sciences of China Agricultural University and head of the “double-cropping maize trial and demonstration project.”
Due to low spring temperatures, spring maize in Hebei Province is generally sown in late April or early May and harvested in late August. “In recent years, as the climate has warmed, the accumulated temperature in spring in the Hebei region has increased by 260°C. On this basis, we used film-mulched sowing technology to advance the sowing time of spring maize to mid-March, so that it can be harvested in mid-July.” Chen Xinping explained.
Double-cropping maize can save 30%-50% of water
In 2012, the High-Yield and High-Efficiency Modern Agriculture Research Base (Quzhou) of China Agricultural University began double-cropping maize trials, that is, exploring the replacement of the traditional “winter wheat—summer maize” cropping pattern with “spring maize—summer maize.” This trial focuses on improving and adjusting the future cropping structure in China's North China region under changing climate and resource and environmental conditions, and explores the establishment of ecologically conserving agriculture that can both increase yields and save water, save fertilizer, and allow fallow.
The biggest problem in agricultural production in the North China region is water shortage. Winter wheat requires at least three irrigations from sowing to harvest, and as many as four or five at most, consuming large amounts of groundwater. Some counties and districts in Hengshui City have already provided subsidies to encourage farmers to give up growing wheat and switch to other crops, in order to avoid continued overexploitation of groundwater. “Replacing winter wheat with spring maize requires only one to two irrigations, and summer maize sown during the rainy season in July generally does not need irrigation, so over the whole year two irrigations can be saved, and water savings can reach 30%-50%.” said Cui Zhenling, an associate professor at the College of Resources and Environmental Sciences of China Agricultural University, by way of comparison.
However, the spring maize variety in the double-cropping maize model cannot be chosen arbitrarily. After many trials, the double-cropping maize trial and demonstration project team selected “Demeya,” a spring maize variety widely planted in the high-latitude regions of Northeast China. This spring maize is cold-tolerant and has a short growth period. Sown in mid-March and harvested in mid-July, it allows the second season's summer maize to be sown by the latest deadline in mid-July (in the Hebei region) and to mature in mid-November.
Double-cropping maize can create a 4-month fallow period
In the traditional cropping pattern, because summer maize produces a large amount of straw, it is relatively troublesome to handle. And in order to rush the sowing of winter wheat, farmers often harvest summer maize before it is fully mature, when the straw is still green, making mechanized return-to-field operations difficult. With double-cropping maize, the amount of straw is doubled, so would it not be even harder to handle?
“The double-cropping maize model can easily achieve full return of maize straw to the field.” Cui Zhenling said that the spring maize “Demeya” is suitable for dense planting, and its stalks are thin and dry easily, so they can be mechanically crushed and returned to the field directly at harvest without affecting the sowing of summer maize; summer maize matures in mid-November, and because there is no longer a need to rush the farming season, harvest and straw return operations can be carried out after the straw has dried thoroughly.
It should be noted that after the second season's maize straw is crushed, it is not plowed under but directly left as mulch on the soil surface. This is because there is a 4-month idle period after summer maize harvest and before spring maize sowing the following year. If the soil were left bare, it would cause problems such as loss of organic matter in the topsoil, reduced soil moisture, and dust. More importantly, a 4-month fallow period is achieved in winter, when land productivity is lowest, restoring soil fertility on the one hand and achieving optimal use of the land on the other.
Under the double-cropping maize model, straw, which “everyone finds annoying,” is transformed into an indispensable treasure for covering the soil surface and protecting cultivated land.
Double-cropping maize can reduce potassium fertilizer use by 50kgK2O/hm2
Full return of double-cropping maize straw to the field can also greatly reduce potassium fertilizer use. In the Huang-Huai-Hai region, potassium fertilizer use can be reduced by 50kgK 22O/hm, and maintaining 90kgKO/hm22 for two seasons a year is sufficient. This is because potassium in maize plants is mainly concentrated in the stalks, and straw buried in the soil can release most of the potassium in a very short time.
Reducing potassium fertilizer use is of particular significance to China. “China's potassium fertilizer reserves account for only 1.6% of the global total, while its use accounts for 20% of the global total. Price fluctuations in imported potassium fertilizer have become an important factor affecting China's fertilizer market. The full return of double-cropping maize straw to the field is an efficient potassium fertilizer substitution technology. If it is promoted on a large scale in the Huang-Huai-Hai region, it will help ease China's dependence on imported potassium fertilizer.” said Guo Qiang, deputy general manager of the Potassium Fertilizer Business Division of Sinochem Fertilizer Co., Ltd.
Double-cropping maize can increase yields by 20%-30%
Double-cropping maize can save water, save fertilizer, and allow fallow. What about its yield? Trial data from 2012 to 2014 at the China Agricultural University Quzhou “Double-High Base” show that under conventional water and fertilizer management, double-cropping maize yields reached as high as 1.5 tons/mu, 12% higher than high-yield farmers growing winter wheat—summer maize, and 20%-30% higher than ordinary farmers.
The 200-mu double-cropping maize demonstration plot uses the contracted land of Fan Changyong, secretary of the Party branch of Lianzhu Village. He told the reporter: “The drought this year has been severe, and our village's wheat harvest was not very good. But the spring maize on the demonstration plot did fairly well, producing 650 kilograms per mu. The summer maize has now been sown, and the rain has been good these past few days, so this season's yield will be higher.”
Through processes such as film-mulched sowing to capture accumulated temperature, short-growth-period spring maize to fit the crop rotation window, crushing summer maize straw and leaving it as surface mulch, and deep plowing of straw during spring land preparation, the project team achieved a clever combination in time and space of factors including water resources, climatic conditions, variety selection, mechanized operations, and conservation tillage technology, completing the technological integration of the entire double-cropping maize model. “It can be said that the double-cropping maize model is already mature and has the conditions for large-scale promotion in the North China Plain.” Chen Xinping said with great confidence.
Reporter's Notes
Four Questions About “Double-Cropping Maize”
Each technology in the double-cropping maize planting model looks very ordinary, with nothing special about it. However, when these conventional technologies are scientifically and skillfully combined, they create a cropping model of breakthrough significance. It truly is a case of “what seems most ordinary is actually most extraordinary, and what seems easy was in fact arduous.” But after the interview, the reporter still had some points of confusion, which fortunately were answered in detail by relevant experts.
First, since spring maize (Demeya) has a short growth period and high yield, why not plant it again for the second season? Demeya is a dense-planting-tolerant variety, and 6000 plants can be planted per mu, whereas traditional spring maize in Hebei has only 4000. But it has poor disease resistance and is not suitable for growing in the high summer temperatures of the Huang-Huai-Hai region.
Second, what is the significance of choosing mid-July as the sowing period for summer maize in the double-cropping maize model? Traditional summer maize in the North China region is generally sown in June, with the latest sowing deadline in mid-July. The summer maize in double-cropping maize is sown right at this time, and since there is more rain in July, there is no need to irrigate at the seedling stage.
Third, China's North China Plain is the world's largest “funnel area.” Since water is so scarce, why not promote drip irrigation? Drip irrigation equipment is costly, and if the yield increase brought by drip irrigation does not exceed 20%, it is not worthwhile for farmers unless water is extremely scarce. Therefore, double-cropping maize has the cost advantage of saving water.
Fourth, since returning straw to the field can basically maintain the potassium balance in the soil, is it possible to apply less or no potassium fertilizer? Potassium mainly exists in the stalks of the plant and can improve the stalk's resistance to breaking. Increasing the level of potassium supply is one of the necessary measures to enhance maize lodging resistance and thereby achieve high maize yields.