What new fertilization methods are there for hybrid corn seed production?

Corn is a crop with high fertilizer demand; at different growth stages it requires different types and amounts of fertilizer, and the higher the yield, the more fertilizer is applied. We abbreviate as the old method the fertilization approach that puts heavy emphasis on base fertilizer and ear fertilizer and light emphasis on seedling fertilizer and stalk fertilizer, that is, heavy at both ends and light in the middle; and we abbreviate as the new method the fertilization approach that puts heavy emphasis on base fertilizer and stalk fertilizer and light emphasis on seedling fertilizer and ear fertilizer, that is, two heavy and two light. The main difference between the new and old methods is the amount of stalk fertilizer and ear fertilizer applied to the female parent: the new method advocates heavy application of stalk fertilizer, while the old method adopts heavy application of ear fertilizer. In many years of practical corn seed production, we found that the new method better meets the normal growth and development needs of the female parent and is more conducive to increasing seed production yield. After 3 consecutive years of production application with different varieties, the new method increased yield by more than 10% on average compared with the old method, and we have worked out a new fertilization method for corn seed production that has achieved very good results.

1 Main contents of the new method

Fertilization of the female parent: First, according to the different female parent types, soil conditions and yield design requirements, determine the type and total amount of fertilizer to be applied. For every 100 kg of seed produced, generally 7 kg of pure N, 3-4 kg of sulfur dioxide, and 6-8 kg of hydrogen oxide need to be applied; the total amount of fertilizer is calculated according to this standard. For some plots lacking zinc, 2-3 kg of zinc fertilizer should also be added per 667 sq m. Second, the fertilization principle of sufficient base fertilizer, early seedling fertilizer, heavy stalk fertilizer, and timely ear fertilizer should be mastered. Base fertilizer should be mainly farmyard manure and phosphorus and potassium fertilizer, while topdressing should be mainly nitrogen chemical fertilizer and compound fertilizer. The amount used at each stage is 30% for base fertilizer, 20% for seedling fertilizer, 40% for stalk fertilizer, and 20% for the ear stage.

Fertilization of the male parent: The male parent should be managed with high fertilizer and water, topdressing small seedlings to make them larger and weak seedlings to make them strong, and it should be kept in balanced development with the female parent. If the male parent is found to be late, quick-acting nitrogen fertilizer should be applied in advance and foliar spraying should be carried out; if the male parent is found to be early, fertilization should be controlled, watering should be reduced, and deep intertillage should be carried out to control its growth.

2 Analysis of the reasons why the new method increases yield

Heavy application of stalk fertilizer meets the high fertilizer demand at the jointing and booting stage. The amounts of nitrogen, phosphorus and potassium absorbed by corn at different growth stages differ significantly. According to the literature, spring corn accounts for 3% at the seedling stage, 49% at the jointing stage, 22% at the flowering stage, and 26% at the maturity stage; summer corn accounts for 10% at the seedling stage, 63% at the jointing stage, and only 22% at the flowering and maturity stages. The jointing stage is the period of greatest fertilizer demand. During this period, spring corn absorbs 32%, 45% and 70% of its total absorption of nitrogen, phosphorus and potassium from the soil, respectively, while summer corn absorbs 76%, 63% and 67%, respectively. Heavy application of stalk fertilizer can meet the needs of normal growth and development of corn.

Heavy application of stalk fertilizer is conducive to strong stalks, large ears and many grains. Stalk fertilizer is generally applied at the jointing stage 30 d after emergence. Heavy application of stalk fertilizer can promote stem and leaf growth and the formation and development of the female ear, prevent degeneration of the florets at the top of the female ear, and thereby produce strong stalks, long ears and many large grains.

Timely detasseling of the female parent reduces nutrient consumption. To ensure seed purity quality, seed production fields mostly adopt detasseling by feeling the husk with leaves retained. The tassel is one of the growth centers of corn. Timely removal of the tassel can reduce large nutrient consumption, increase ventilation and light penetration, and is more conducive to the development of the female ear, so that the ear emerges quickly and uniformly and silking occurs 2-3 d earlier. Farmers call early detasseling equivalent to applying fertilizer once.

Heavy application of ear fertilizer is unfavorable for increasing seed production yield. Heavy application of ear fertilizer easily causes excessive nutrition and excessive vegetative growth, making the husk leaves thicker and longer, with small leaves growing on the husk leaves, commonly known as ear-like leaves. Sometimes it can also cause small ears to grow on the ear, commonly known as an ear cluster, with more than two ears growing in one cluster, and it also makes silking of the female ear difficult, weakens pollination compatibility, leads to poor seed setting rate of the ear, and causes delayed maturity with excessive vegetative growth, so that nutrients in the plant cannot be transferred to the ear relatively quickly. Therefore, excessive application of ear fertilizer is not conducive to improving the quality and yield of hybrid corn seed production.