A few touches on fertilizing spring crops: Maize likes and brings on nitrogen...Sunflowers don't bring on much nitrogen. Legumes don't care for mineral nitrogen at all. But they all love phosphorus soft heat for seeding... It's good that you're already using phosphorus and have seen the difference and its importance. Now you're left with potassium - it's the one that will boost your yield level, as long as you understand it and loosen your purse strings for it. He is ingenious, but quite shrewd in his services. It's not just oilseeds and root crops that respond to potassium, it's all crops.
When sowing both crops, it is good to have some phosphorus around the seed, which provides warmth and first food for the seeds and their fragile roots and sprouts. We sow these crops in early spring, the soil is not warm enough, so this phosphorus creates a comfort around the young plant. This is most easily done by fertilizing at sowing time, but can also be done beforehand with light incorporation. It is a good idea to place these fertilisers 4-5 cm to the side or below the seeds. This phosphorus is not sufficient for the whole growing season and it is not sensible to apply the whole rate with sowing, it may even be harmful. About 3-4 kg/dca of active substance we provide here. Phosphorus as a nutrient - I have stressed this many times, is an element for basic stocking throughout the rotation.
PHOTO - PHOSPORUS DEFICIENCY - Source V. Bergman, 1993.
Maize starts nutrient uptake most intensively at the 6-8 leaf stage. At leaf 5, ear formation begins. Between the 6-8 leaf stage, the tassel forms. So - remember - in this period it is important to provide the plants with the most optimal conditions for development - enough food, water, air and light. This means that at this point you have given the maize the most important food and it is weed-free, not just at this stage watering it with a shower of herbicides. At this time, a severe cold snap can also do a lot of damage to the broomrape and there will be no full pollination later on. I would split the nitrogen into 3 parts - 70% before, 10% at sowing and 20% around leaf 5-6. Later nitrogen application has some risks. But if we water, the pattern is quite different and the dose higher.
In the 5-8 leaf phase, I recommend bringing in the essential trace elements, as well as magnesium and the further element potassium. Maize, as you know, responds very well to fertilisation with organic fertilisers. This includes green manuring. Which means that sowing catch crops before maize make a lot of sense. And don't forget the sulphur - either with the nitrogen pre-sowing and or foliar.
One of the most important things when growing maize is to aim to synchronise the ear and flower formation processes. This is done primarily through uniform sowing. Aligned soil! And not too deep! 4-6 cm is enough! And the other lever - stimulating the initial development by broadcast phosphorus fertilisation. Phosphorus is mostly blocked in cold weather and on structureless soils, but you need to have an analysis done to know if it's there to be blocked, or rather not enough.
And one more thing to mention - higher feed rates are needed to produce silage with high volume and good grain and energy content than maize for grain. I know that the opposite is often practiced in this country.
Everybody is already aware of the need for zinc in maize, but I dare say that it is sometimes overdone and every spot is diagnosed as zinc starvation. To distinguish, note that vein chlorosis here starts in the leaf axils. As opposed to manganese deficiency.
PHOTO – MANGANESE DEFICIENCY – Source V. Bergman, 1993.
PHOTO – ZINC DEFICIENCY - Source V. Bergman, 1993.
PHOTO – BORON DEFICIENCY - Source photo archive K+S 
Boron is very important for cob maturation and is so far the least used trace element in cereals in Bulgaria, but you can be sure that its effect is great. And once again to remind: for roots and chlorophyll - magnesium. For water balance and health - potassium, and BORОN is needed anywhere you want to have grain, oil, quality. All cereals need boron for good ripening. Maize with its large habit and large cob especially so.
Feeding sunflower: it is very aggressive to the nutrient reserves in the soil. It extracts a lot, returns nothing. Apart from that, he wants a long rotation, which 90% of the farming community does not follow. This requirement is mostly related to the large fungal pathogen background that settles on sunflower - it is attacked by many economically important diseases, but also the soil after it needs time to recover its soil fertility, and whoever practices wheat-sunflower-wheat-sunflower will soon see that his yield from cereals is also going down steeply and steadily. Think it through, improve it, don't get carried away - the basis of good practice is a diverse rotation.
What does a sunflower need for 100 kg of production - it needs to absorb in active matter about 4-5 kg of nitrogen, 2-3 kg of phosphorus, 10 kg of potassium, 1 kg of sulphur and over 1 kg of magnesium - very roughly. According to various sources, potassium is as high as 18 kg/dca per 100 kg of production. In any case, this is a markedly potassium-loving crop. Sunflower yields respond very well to high rates of phosphorus, potassium, magnesium, sulphur and calcium. The case of nitrogen fertilisation is controversial. With excessive nitrogen supply, initial development is stunted, more precisely, roots become sluggish, the environment around the plants can turn sour and vegetative development is prolonged. On the other hand, sunflower absorbs nitrogen most strongly from the formation of the panicles until the end of flowering. This leads to the conclusion that it is better to have either a slow-release nitrogen fertiliser, or to use inhibitors, or to fertilise twice. When fertilising twice, slow-release fertiliser should not be used for the second dose so as not to delay ripening. If nitrogen is overdosed, there is also a risk of sunflower vegetative growth, which will reduce grain yield. Sulphur is very important, both as a nutritional element and as a fungicide shield. The enormous leaf surface of sunflower also determines the high need for magnesium.... for ripening is well known and the great need for boron, preferably twice - at the beginning of the vegetation and before flowering. Another important element, especially on acid soils, is molybdenum. It was once the practice to treat the seeds, but better to bring it in towards the 3-4 leaf stage. On acid soils it is better not to look after sunflower, but if it is unavoidable, calcium is necessarily given. One final touch: a huge percentage of sunflowers in Bulgaria are technological. After the herbicides have been applied, which should not be too late, I strongly recommend that you vitalize it with the necessary trace elements and be sure to add an amino acid product. Mixing any foliar fertilizer with a herbicide is not right, I know you would like to and it is easier, but the split approach is much more efficient.
Agriculture is based on a lot of agronomic knowledge about patterns, interrelationships in nature, precise plant and soil science; a lot of chemical knowledge - not just to poison nature, but to know how the elements of the Mendeleev table and tons of active substances with loud commercial names affect our crops. There is no "almost" in knowledge - you either know things or you don't. But practical farming asks of every farmer/rancher/tenant farmer/rancher/agronomist, etc. a lot of observation, analytical ability, flexibility, a quick combinative mind, and organizational skills. If we don't know something - we will find who knows it or where to read it. But if we don't have the organizational will and technological discipline, if we don't strive for new knowledge and self-criticism, and if nature is always to blame, then there will always be an unsatisfactory "almost" as an end result, and in today's competitive environment, that is not a positive word in the vocabulary of a successful manager/CEO/chairman/owner/leader. Wishing you a successful spring campaign!
Certified Agricultural Engineer Evelina Marinova
Leader Consulting EOOD
16.01.2022