Detailed Classification of Wheat Seedlings: Targeted Management Is Key

@#@245@#@After emergence, various types of weak seedlings often form due to the influence of natural conditions and cultivation practices. To prevent weak seedlings and manage them according to their specific symptoms, the details are introduced below:

Weak seedlings caused by soil drought mostly occur in wheat fields with insufficient subsoil moisture or where moisture escapes through cracks. Their characteristics are: slow tillering, grayish-green leaf color, short and small heart leaves, slow or stagnant growth (known among farmers as "shrinking-heart seedlings"), gradual yellowing and drying of the middle and lower leaves, and few and thin roots. Key management points: combined with irrigation, apply 15 kg of ammonium bicarbonate per mu.

Weak seedlings caused by soil nitrogen deficiency are thin and weak, standing upright, with reduced tillering, narrow and short leaves, and lower leaves that gradually turn yellow and dry starting from the leaf tips and progressing toward the upper leaves. Key management points: apply 7-8 kg of urea per mu, or 20-25 kg of ammonium bicarbonate, by banding it in furrows between rows or applying it dissolved in water.

Weak seedlings caused by soil phosphorus deficiency show poor root development, few and weak secondary roots, dark green and lusterless leaf color, purple-red leaf tips and leaf sheaths, stunted plants, and reduced tillering. Key management points: combined with irrigation and hoeing, apply 20-30 kg of superphosphate per mu by opening furrows between rows; the earlier the application, the better the effect.

Weak seedlings caused by waterlogged and compacted soil or saline-alkali damage usually show poor root development, weak absorption capacity, and slow tillering, often accompanied by nutrient deficiency symptoms; in plots with severe saline-alkali damage, patches of purple-red "stunted old seedlings" often appear, with the basal 1-2 leaves yellowing and drying, and in severe cases, seedlings dying in patches. Key management points: combined with deep intertillage, open furrows and apply a mixed nitrogen-phosphorus fertilizer; in plots with severe saline-alkali damage, irrigate after fertilization to leach salts, and promptly hoe and loosen the soil to break up crusting.

Weak seedlings caused by hard, compacted soil result from a lack of moisture and air in the soil, which makes root extension difficult, causing wheat leaves to be yellow and short and tillers to fail to appear on schedule. Key management points: first irrigate promptly, then carry out deep intertillage to loosen the soil and break up the hard layer.

Weak seedlings caused by excessively wet soil usually show pale purple leaf color, slow tillering, and in severe cases, leaf tips turning white and drying. Key management points: first carry out timely deep intertillage to reduce moisture and improve aeration, then apply a small amount of quick-acting chemical fertilizer to promote early seedling growth.

Weak seedlings caused by excessive seeding rate present as: overcrowded seedlings and thin, spindly plants. Key management points: first thin the seedlings promptly, especially the "clumped seedlings" at field corners, edges, and within the field, thinning early and severely, then combined with irrigation, apply a small amount of quick-acting nitrogen and phosphorus fertilizer to compensate for the excessive consumption of soil nutrients and help the wheat seedlings turn from weak to strong.

Weak seedlings caused by too-deep sowing present as: slow emergence, long and slender leaf sheaths, delayed tillering, and no secondary roots. Key management points: first remove soil to expose the crown, then apply fertilizer promptly (15 kg of ammonium bicarbonate per mu) to promote root and seedling development.

Weak seedlings caused by too-shallow sowing result from the tillering node being too close to the soil surface, leading to poor moisture and nutrient conditions, which inhibit root growth and tiller bud development, thus usually presenting as reduced roots and tillers, yellow and weak plants, and susceptibility to freezing and death. Key management points: combined with hoeing, mound soil around the roots; when aboveground growth basically stops, break the ridges and cover with soil. The soil cover thickness should be such that the tillering node is about 3 cm below the surface; if soil from elsewhere is used for covering, that is, clay to cover sand or sandy soil to cover clay, it can also improve the soil.

Weak seedlings caused by too-late sowing are mostly due to a short growing period before winter and insufficient accumulated temperature, resulting in thin and weak wheat seedlings with few tillers. Key management points: focus on hoeing and supplemental fertilizer and water, applying 15 kg of ammonium bicarbonate per mu at the three-leaf stage; for wheat fields with poor soil moisture and rapid water infiltration, irrigate for tillering promptly after the three-leaf stage (but for plots with suitable moisture or heavy, poorly draining soil, irrigation is not advisable before winter); for the last hoeing before freezing, pay attention to mounding soil around the roots to protect the seedlings through winter safely.