â– sowing too late, the short growth period, accumulated temperature is not enough to cause the ball is not tight. â– Although the seeding period is relatively punctual, due to lack of light, it will also result in loose balling. â– The lack of temperature and light during the late growth period may cause the ball to become tight. â– Insufficient fertilizer and water, especially during the ball-breaking period, lack of nutrients, resulting in not tight ball. 7 Inch Face Access Control,Face Recognition Access Control With Fingerprint,7 Inch Ultra Thin Face Recognition Terminal,Dual Camera Recognition Access Control System Chongqing Huifan Technology Co., Ltd , https://www.huifantech.com