Yellowing of green feather during maturing of onions turnip is normal and correct process. Here nutrients ""flow"" from leaves in the formed turnip. And here if plumose leaves gain sickly yellow color in May, June is problem which is required to be solved immediately. Otherwise, the harvest will grow poor.
The first and most popular cause of yellowing of onions during active growth in May and June – the shortage of nitrogen in power supply.
Onions plants sharply react to lack of nitrogen both in dry weather, and in rainy. From the dry soil of plant cannot take nitrogen, and all power supply comes to roots only in the form of solutions.
After abundant precipitation, nitrogen goes to base layers of the soil and there is impoverishment of the soil. And here nitrogen-containing fertilizing which is easily acquired and thanks to which onions quickly restore the growth and saturation of color of leaves will come to the rescue. It is possible to use nitrogen mineral fertilizers (urea, ammonium nitrate) or to apply complex complex fertilizers with the high content of nitrogen, for example, to use nitroammofosky, nitrophoska.
Organic fertilizers perfectly work at the initial stage of growth of onions also. It is 5-7-day infusion of weed plants, especially nettles, clovers. Any extract from manure will approach. It is possible to combine organic and mineral fertilizers.
The harm done by larvae of onions fly is other reason of yellowing of onions. To make sure of it, it is necessary to pull out bulb from the soil, to examine collum and roots, to cut it. Inside the cavity of onion will have the diluted fabric with unpleasant smell in which it is possible to see worms – larvae of onions fly. The emergency help in this case – onions are watered in the evening with salt solution. Take 200 g of food table salt, part in 10 liters of water and accurately water at the roots, avoiding hit on green feather. Two weeks later do repeated processing.
One more national way which at the same time will help to get rid of worms of onions fly and will feed up plants digestible nitrogen is ammonia solution from pharmacy. It is necessary to part three tablespoons in 10 liters of water and to water onions at the roots in the evening.