Influence of Controlled Drainage on the Groundwater Nitrogen and Phosphorus Concentration at Jointing-Booting Stage of Wheat

Table 1

Design of controlled drainage scheduling.

Treatments	Tillering stage/mm	Jointing-booting stage	Panicle initiation stage/mm	Milky stage/mm
T1	≤−600	100 mm (1 d) (3 d-400)	≤−1000	≤−1000
T2	≤−600	100 mm (1 d) (3 d-800)	≤−1000	≤−1000
T3	≤−600	100 mm (3 d) (3 d-400)	≤−1000	≤−1000
T4	≤−600	100 mm (3 d) (3 d-800)	≤−1000	≤−1000
T5	≤−600	≤−800	≤−1000	≤−1000

Note: mm( d) ( d − mm): mm fixed water level was kept with duration of day at Jointing-booting stages from the soil surface and drained to − mm in days. <− mm: − mm was the upper limit of groundwater level, if groundwater level exceeded the value and drainage would be conducted. T1, T2, T3, and T4 denote different controlled treatments at jointing-booting stage; T5 as the control indicates conventional subsurface drainage.