Effects of fertigation and micro-spraying on growth of flue-cured tobacco, soil properties and water use efficiency
The use of water saving irrigation systems and technology is of great significance in tobacco production in central China due to the high frequency of drought in the early tobacco growth stages. In recent years, micro-spraying irrigation and fertigation systems were introduced in tobacco production, and field experiments were set up separately to investigate the effects of these techniques on plant growth, soil properties, tobacco productivity and quality, and water use efficiency. The treatment of micro-spraying experiments included three micro-spraying amounts (12 mm, 24 mm, 36 mm each irrigation, two irrigations total for each treatment) with conventional furrow irrigation (60 mm each irrigation, also two irrigations total) as control. The fertigation experiment included three nitrogen applications (54 kg-N, 46 kg-N, 39 kg-N per hectare) with conventional furrow irrigation and 54 kg-N per hectare as control. The results of the micro-spraying experiment showed that micro-spraying two times with 24 mm each time promoted tobacco growth, resulting in best performances of agronomic traits. With the increase of irrigation quota, the depth of moistened soil and soil volume weight increased, and furrow irrigation resulted in too deep moistened soil that lead to lower available nitrogen content in the layers of 0-30 cm depth. Irrigation significantly increased tobacco yield and value, with micro-spraying 24 mm each time having the highest yield and value for three consecutive years. Total water productivity for micro-spraying 24 mm per time was 23.24 % higher than that of furrow irrigation, followed by micro-spraying 36 mm per time. The results of the fertigation experiment showed that fertigation by drip pipe significantly increased water use efficiency and nitrogen use efficiency, so the amount of nitrogen applied should be decreased by 15-20 % compared with the conventional furrow irrigation method to ensure timely mature, high maturity and high quality tobacco production. Fertigation and micro-spraying proved to be two ideal alternatives to replace traditional furrow irrigation by showing significantly high water and nitrogen use efficiency, improved leaf quality and value.