When is the best time to sow spring corn? How long after sowing does it germinate? When to fertilize? How to fertilize? (With sowing times for various regions)
Every April, most regions of our country begin sowing corn, but due to climate factors in different places, growing corn well still requires mastering certain techniques, so when is the best time to sow spring corn? How long after sowing does it germinate? When to fertilize? How to fertilize?
Sowing time:
The sowing period for spring corn is generally from late April to early May. After corn is sown, only when the soil temperature at 10 cm stably passes 12°C will it achieve germination in 7 days. If the soil temperature does not reach this level, the corn seeds will remain in the soil for too long, which will affect the germination rate, and the seeds that barely germinate will also form weak seedlings. Therefore, farmers are reminded that this year's spring-sown corn must be sown at the right time according to temperature changes.
Do not sow too early. Spring corn does not have higher yields the earlier it is sown. Planting too early not only results in lower yields, but also causes quite severe pest and disease problems, such as rough dwarf disease, red spider mites, and corn leaf blight and spot diseases. This is because corn planted at this time is in the pollination and grain-filling stages during the hot and rainy season, which easily causes bare tips or missing grains. It is understood that only when planted 15-20 days before the local wheat harvest is the period when corn can achieve the highest yield.
In addition, suitable varieties should be selected. When choosing corn varieties, not only should they adapt to the local weather and climate, but their comprehensive characteristic indices such as lodging resistance and stress resistance should also be considered; otherwise, severe bare tips and shriveled grains can easily occur.
Growth cycle:
After corn seeds are sown, imbibition can be observed on the 1st day, and the embryo begins to germinate.
One week later, these small sprouts break through the soil; under sunlight, the pale yellow sprouts gradually turn green.
At around 27 days, the seedlings gradually grow larger and begin jointing.
At 52 days, corn silks begin to emerge, and male pollen appears at the top; at about 90-100 days, after female and male fertilization, the corn ear grows larger and larger, and the corn silks gradually dry up or fall off, forming a corn ear.
Fertilization time and techniques:
Within a certain range, corn yield increases as fertilizer application increases. Accurately determining the fertilizer application rate is an important issue for achieving high, stable, and efficient corn yields. However, how to determine the fertilizer application rate is a very complex issue.
When corn grows and develops to form yield, the nutrients absorbed include both nutrients stored in the soil and nutrients from fertilizer applied in the current season. The amount and proportion of nutrients absorbed from soil storage or fertilizer are affected by many factors combined, so accurately determining the fertilizer application rate is somewhat difficult. Theoretically, there are many methods for determining corn fertilizer application rates, but they are all relatively complex.
Where conditions permit, soil testing and fertilizer recommendation can be carried out, testing the content of various nutrients in the soil once every 3-5 years, and then roughly calculating the fertilizer application rate using the formula below based on factors such as corn nutrient requirements, planned yield, soil nutrient supply capacity, and current-season fertilizer use efficiency.
I. Nutrient requirements of corn
1. Characteristics of corn nutrient demand at different growth stages
The proportion of nutrients required by corn differs at each growth stage. From emergence to jointing, corn absorbs 2.5% nitrogen, 1.12% available phosphorus, and 3% available potassium; from jointing to flowering, it absorbs 51.15% nitrogen, 63.81% available phosphorus, and 97% available potassium; from flowering to maturity, it absorbs 46.35% nitrogen, 35.07% available phosphorus, and 0% available potassium.
Critical period of corn nutrition:
The critical period for phosphorus nutrition in corn is at the three-leaf stage, generally the period when seed nutrition shifts to soil nutrition; the critical period for nitrogen in corn is slightly later than for phosphorus, usually the period when vegetative growth shifts to reproductive growth. The demand for nutrients during the critical period is not large, but the nutrients must be comprehensive and the proportions suitable. If nutrient elements are too much, too little, or unbalanced during this period, it will have obvious adverse effects on corn growth and development, and no matter how the deficient nutrient elements are supplemented afterward, it will be of no avail.
Period of maximum nutrient efficiency in corn:
The period of maximum efficiency in corn is the large trumpet stage. This is the period when corn nutrient absorption is fastest and greatest. During this period, both the absolute and relative amounts of nutrients required by corn are the largest, the absorption rate is also the fastest, and the effect of fertilizer is the greatest. When the fertilizer application rate is appropriate at this time, the yield-increasing effect on corn is most obvious.
2. Nutrient demand of corn throughout the entire growth period
Corn growth requires absorbing various mineral nutrient elements from the soil, among which nitrogen is the most, followed by potassium, and phosphorus ranks third.
Generally, for every 100 kg of grain produced, it is necessary to absorb 2.5 kg of pure nitrogen, 1.2 kg of phosphorus pentoxide, and 2.0 kg of potassium oxide from the soil. The ratio of nitrogen, phosphorus, and potassium is: 1:0.48:0.8.
Fertilizer application rate=(planned yield requirement for a certain element - soil supply of a certain element)/(content of a certain element in fertilizer (%)×current-season fertilizer use efficiency (%)). Fertilizer use efficiency varies greatly. According to experiments, the current-season use efficiency of general organic farmyard manure is about 30%, that of nitrogen fertilizer is about 40%-50% (calculated as 40%), and that of phosphorus and potassium fertilizers is about 30%-40% (calculated as 30%).
Question: For a planned yield of 500 kg of corn grain per mu, how much fertilizer needs to be applied? Assume that during the soil survey, the soil nitrogen content per mu was 17 kg, phosphorus pentoxide was 6.0 kg, and potassium oxide was 14.4 kg. The soil nutrient use efficiencies are 50% for nitrogen, 70% for phosphorus pentoxide, and 30% for potassium oxide. According to the national fertilizer experiment average, when the yield per mu is 500 kg, for every 100 kg of grain produced, the nitrogen requirement is 2.9 kg, phosphorus 1.2 kg, and potassium 2.4 kg. Calculate the application rates of urea, superphosphate, and potassium chloride (urea contains 46% available nitrogen, superphosphate contains 16% available phosphorus, and potassium chloride contains 50% available potassium).
II. Corn fertilizer application rate
1. Determine the target yield
The target yield is the yield to be set for the corn planted that year, and it is determined by the soil fertility level of the cultivated land. In addition, the average corn yield of the plot over the previous 3 years can be increased by 10%-15% as the corn target yield. For example: a certain plot has relatively high-fertility soil, and the planned corn yield for the year is 600 kg. The nitrogen, phosphorus, and potassium nutrient amounts required throughout the corn growth period are 15 kg, 7.2 kg, and 12 kg respectively.
2. Calculate the soil nutrient supply
Determine how much available nutrient the soil contains, then calculate how much nutrient is contained in 1 mu of land. The surface soil of 1 mu is calculated at 20 cm, totaling 150,000 kg of soil. If the measured value of soil alkaline hydrolyzable nitrogen is 120 mg/kg, the measured value of available phosphorus content is 40 mg/kg, and the measured value of available potassium content is 90 mg/kg, then the total amount of available alkaline hydrolyzable nitrogen in 1 mu of soil is: 150,000 kg×120 mg/kg×10 to the negative 6th power=18 kg, the total available phosphorus is 6 kg, and the total available potassium is 13.5 kg.
Because various soil factors affect the availability of soil nutrients, not all available nutrients in the soil can be absorbed and utilized by corn, so a soil nutrient correction coefficient must be multiplied. Research on formula fertilization parameters in various provinces of our country shows that the correction coefficient for alkaline hydrolyzable nitrogen is between 0.3-0.7, the correction coefficient for available phosphorus is between 0.4-0.5, and the correction coefficient for available potassium is between 0.5-0.85.
The use efficiencies of nitrogen, phosphorus, and potassium chemical fertilizers are: nitrogen 30%-35%, phosphorus 10%-20%, and potassium 40%-50%.
3. Determine the corn fertilizer application rate
With the nutrient amount required throughout the corn growth period, the soil nutrient supply, and the fertilizer use efficiency, the corn fertilizer application rate can be calculated directly. Then convert the pure nutrient amount into the actual amount of fertilizer, and it can be used to guide fertilization. Based on the data in 1 and 2, for a corn yield of 600 kg per mu, the required pure nitrogen amount is (15-18×0.6)÷0.30=14 kg. The phosphorus amount is (7.2-6×0.5)÷0.2=21 kg. Considering the obvious residual effect of phosphate fertilizer, the phosphate fertilizer can be applied at half, that is, 10 kg. The potassium amount is (12-13.5×0.6)÷0.50=8 kg. If diammonium phosphate, urea, and potassium chloride are applied, then per mu, 20 kg-22 kg of diammonium phosphate, 22 kg-25 kg of urea, and 14 kg of potassium should be applied.
4. Application of micronutrient fertilizers
Corn is very sensitive to zinc. If the available zinc in the soil is less than 0.5-1.0 mg/kg, zinc fertilizer needs to be applied. The availability of zinc in soil is higher under acidic conditions than under alkaline conditions, so alkaline and calcareous soils are now prone to zinc deficiency. In areas where phosphate fertilizer has been applied for a long time, due to the antagonistic effect between phosphorus and zinc, zinc deficiency is easily induced and should be supplemented. Commonly used zinc fertilizers include zinc sulfate and zinc chloride. The application rate as base fertilizer is 0.5-2.5 kg per mu, for seed dressing 4-5 g/kg, and for seed soaking the concentration is 0.02%-0.05%. If the compound fertilizer contains a certain amount of zinc, there is no need to apply zinc fertilizer separately.
III. Corn fertilization methods
1. Base fertilizer
2000-3000 kg of organic fertilizer, all phosphate fertilizer, 1/3 nitrogen fertilizer, and all potassium fertilizer are used as base fertilizer or seed fertilizer. It can be applied all at once into the sowing furrow together with plowing and ridge raising, so that the fertilizer is applied into the 10-15 cm plow layer. All chemical fertilizers can be used as base fertilizer.
2. Seed fertilizer
Seed fertilizer is the most economical and effective fertilization method. There are many ways to apply seed fertilizer, such as: seed dressing, seed soaking, band application, and hole application. For seed dressing, humic acid, biological fertilizer, and micronutrient fertilizer can be selected. Dissolve the fertilizer, spray it on the corn seeds, stir while spraying, so that the fertilizer solution evenly adheres to the seed surface, then dry in the shade before sowing.
Seed soaking: Dissolve the fertilizer and prepare a certain concentration, put the seeds into the solution and soak for 12 hours, dry in the shade, and then sow immediately.
Band application and hole application: Chemical fertilizers are suitable for band application and hole application. The amount of chemical fertilizer used as seed fertilizer is 2-5 kg. But the fertilizer must be separated from the seeds; deeper fertilization is better, with a depth of 10-15 cm being appropriate. Urea, ammonium bicarbonate, ammonium chloride, and potassium chloride are not suitable as seed fertilizer.
3. Topdressing
The remaining 2/3 nitrogen fertilizer is used as topdressing. Topdressing is divided into four topdressing periods: seedling fertilizer, stalk fertilizer, ear fertilizer, and grain fertilizer, with the following two periods as the focus:
Stalk fertilizer: Apply within 10 days after jointing, which promotes stem growth and young ear differentiation. Use 1/3 of the nitrogen fertilizer in the topdressing as jointing fertilizer, combined with hoeing and ridging, with a distance of 5-7 cm between fertilizer and seedlings.
Ear fertilizer: Apply the remaining nitrogen fertilizer 10-15 days before corn tasseling at the large trumpet stage, which can promote larger ears and more grains and has a good effect on later grain filling.
Appendix best planting times for spring corn in various regions:
Shandong spring corn sowing time:
Because spring corn is sown early and has a long growth period, the yield is high. In Shandong, spring corn is generally planted in early April and harvested at the end of August.
Northeast spring corn sowing time:
The sowing time is after Grain Rain (around April 20) and before May 10, and harvest is roughly after October 1 and before October 20.
Southern spring corn sowing time:
Corn in the south can be planted in two seasons. In the Yangtze River Basin, spring-sown corn is generally sown at the end of March and early April, and can be picked in early to mid-July.
Hebei spring corn sowing time:
Corn is divided into spring corn and autumn corn. Spring corn is sown in late April and early May and can be harvested in late August; autumn corn must be sown no later than mid-July and is harvested in mid-to-late October.
Anhui spring corn sowing time:
Generally, after the first spring rain arrives, it is the best time to plant spring corn. But now, in order to prevent pest and disease disasters, it is advocated that spring corn should be sown appropriately earlier, generally before mid-April.
Hunan spring corn sowing time:
Generally, spring corn is sown in early to mid-April and harvested in early to mid-August. Summer corn is sown from late May to early June and matures in mid-to-late September.