1. The garlic damage caused by continuous cropping
Due to the long continuous cropping, garlic disease epidemic area is on the rise year by year, has reached more than 16000 hectares.According to many years on the investigation and analysis of continuous cropping diseases with garlic, garlic continuous growing heavier than 15 years of land.Garlic continuous cropping obstacle is not a single disease, but a series of physiological disease and infectious disease to harm the comprehensive performance.Normally starts in mid to late march, its symptom is green leaves turn yellow, dry, death;Growth of root and root disk become brown rot, the roots of the serious death;Plant small garlic, garlic moss thin short, small garlic, serious can't bolting.Generally young garlic shoot yield decreased by 40% - 40%, the garlic yield decreased by 30% - 5%.
2. The causes of continuous cropping obstacle garlic
2.1 the influence of pathogenic organisms
Due to many years of continuous cropping planting garlic, garlic of pathogenic microorganisms in garlic residues in the soil or parasitic leaf, garlic, garlic garlic residues such as tree to thrive in the body, the number increased year by year.Several years of continuous cropping of cultivation, seedling resistance is weak, is easy to be infected.As the root knot nematodes in soil exponentially increase year by year, destroy the garlic root, affecting the normal development of garlic and the garlic phytophthora root rot and leaf blight, sclerotium disease serious year by year.
2.2 nutrient element deficiency or imbalance
Garlic to absorb a variety of nutrients in the soil, and the production period of excess supply nitrogen, phosphorus and potassium element in great quantities, do not pay attention to the organic fertilizer and trace element fertilizer applied, inevitably leads to the imbalance of nutrients required garlic, so that the growth of garlic, declining resistance ability, growth potential, physiological diseases appear deficiency type.
2.3 the poison phenomenon
Garlic in the process of growth and development, will produce some against their harmful substances, and through the root secretion and decomposition of residues accumulation in the soil.Along with the increasing length of continuous cropping of garlic, these harmful substances in garlic field soil accumulation, after reaching a certain degree, can inhibit the normal growth of garlic, resulting in garlic growth, yield potential variation, resistance is lower.
2.4 the soil secondary salinization effect on garlic growth and development
Excessive use of chemical fertilizers, causing the soil salt content increasing, soil salinization.Soil salt accumulation, resulting in soil solution concentration increased, the osmotic potential of the soil increased, garlic root suction fat absorption ability is abate, affect the growth of garlic.In addition, the soil solution concentration is too high, easy to cause element reaches a certain antagonism between effect, thus affecting the garlic to absorb some elements, such as nitrogen fertilizer use, excessive impact k?, ca2?And magnesium 2?Absorption, cause unbalanced nutrient uptake, garlic from growing.With the increase of soil salt, may also affect the survival of beneficial soil microbes, reproduction and activities, lead to affect the growth of garlic was overrun with harmful organisms.
2.5 soil harden and structural difference
Excessive use of fertilizers, mechanical pressure, plastic mulching, frequent irrigation and perennial rotary tillage, soil harden and lead to soil structure damage, air permeability, affect the growth of garlic.
