| Sticky maize is the maize for fress food, with shorter growth stage and requirement of high product quality. To increase yield, quality and nutrient and water use efficiency of sticky maize, this study took Gui Nuo518as experimental crop and systematically and in depth investigated the effect of irrigation treatment at different growth stages on physiology, agronomic traits, dry mass accumulation, yield, fertilizer and water use efficiency of sticky maize under different fertilization level using pot and field experiments, and then proposed optimal supply mode of water and fertilizer for sticky maize on the basis of the experimental results. Pot experiment1had water deficit at different growth stages (A:seeding-early joining, B:later joining-booting and C:booting-flowering stages of maize crop) and defferent water deficit levels [serious water deficit (35%-45%θf,θf is field capacity), medium water deficit (45%-55%θf), mild water deficit (55%-65%θf) and normal irrigation (CK,65%～80%θf)]. The pot experiment2had seven water deficit combinations at different growth stages and four fertilization levels, water deficit at three growth stages (early joining, later joining-booting and booting-tasseling stages of maize crop) and medium and mild water deficit at each stage was from the result of the pot experiment1, and four fertilization levels were no fertilization (Fo), low fertilization (F1,0.15g N,0.05g P2O5and0.15g K2O/kg soil); medium fertilization (F2,0.25g N,0.10g P2O5and0.25g K2O/kg soil); high fertilization (F3,0.35g N,015g P2O5and0.35g K2O/kg soil). The pot experiment3had two fertilization levels (F1and F2from the pot experiment2) and three combinations of water deficit (selected from the result of pot experiment2). The field experiment had four irrigation treatments (IT1: no irrigation at the booting stage, IT2:no irrigation at the flowering stage, IT3:no irrigation at the milky stage, IT4:normal irrigation) and three fertilization levels (FL1:140kgN,70kgP2O5and140kgK2O/hm2, FL2:180kgN,90kgP2O5and180kgK2O/hm2, FL3:220kgN,110kgP2O5and220kg K2O/hm2]. The main findings are outlined as follows:(1) Under the pot condition, compared to normal irrigation, water deficit at the seeding-early joining stage, medium water deficit at the later joining-booting and mild or medium at the booting-flowering stages did not reduce fresh or dry seed yield, water use efficiency based on dry seed yield (WUES), total NPK uptakes of sticky maize and soil available N and P contents significantly, but they reduced water consumption by10.8%-19.8%. Mild water deficit at the later joining-booting stage combined with mild or medium water deficit at the booting-flowering stage did not reduce fresh or dry seed yield and WUES significantly, but they reduced water consumption by15.8%-22.8%. Medium water deficit at the later joining-booting combine with mild water deficit at the booting-flowering stages did not significantly reduce the total NPK uptake of plant and soil available N and P content.(2) Under the pot condition, compared to no fertilization, fertilization improved photosynthetic rate, leaf water use efficiency, fresh or dry seed yield, water use efficiency based on total dry mass (WUEt), WUES and total N, P and K uptakes of stick maize, and medium fertilization level (F2) had highest effect. At F2, compared to normal irrigation, medium water deficit at the early joining stage combined with mild or medium water deficit at the later joining-booting stage (I2,13) and mild water deficit at the early joining-tasseling stage (I5) did not significantly reduce fresh or dry seed yield, WUEt, WUES and total NPK uptake of stick maize, but they reduced water consumption by9.7%,9.1%and12.5%, respectively. However, increased fertilization and any water deficit treatment did not improve fertilizer use efficiency at one season.(3) Under the pot condition, at I3and I5treatments, compared to normal irrigation, water deficit reduced photosynthetic rate (Pn), transpiration rate (Tr) and MDA content, but improved chlorophyll content (Chl) and soluble sugar content (SS) slightly. After rewatering, leaf Pn, Tr, Chl, SS and MDA can be restored to the level of the normal irrigation. Chl and SS contents increased with the increase of fertilization level. At F2, compared to normal irrigation, I3treatment did not significantly affect fresh or dry seed yield, total N, P and K uptakes and seed SS content of stick maize, but improved WUES by18.7%. (4) Under the field condition, compared to normal irrigation, any irrigation treatment did not significantly affect physiological and biochemical indices at the booting and flowering stages. At low fertilization level, no irrigation at the flowering stage (IT2) improved fress ear yield of sticky maize by7.7%and irrigation use efficiency by24.4%, and at medium fertilization level, no irrigation at the booting stage and IT2improved fress ear yield of sticky maize by7.7%and15.4%and irrigation use efficiency by39.9%and33.7%, respectively. Fertilization significantly increased soil available K content, but did not significantly affect shoot N, P and K contents and soil available N and P contents.In summary, water feficit treatment at the seeding-early joining stage, medium water deficit at the early joining stage combined with mild or medium water deficit at the later joining-booting stages, mild water deficit at the early joining-tasseling stage did not significantly affect the physiological and biochemical indices, fresh seed yield and seed quality, but increased water use efficiency. At medium fertilizer level, medium water deficit at the early joining stage combined with mild water deficit at the later joining-booting stages did not affect fresh or dry seed yield, seed quality and total N, P and K uptakes, but increased water use efficiency based on dry seed yield. Therefore, medium fertilization level combined with medium water deficit at the early joining stage plus mild water deficit at the later joining-booting stages is the optimal supply mode of water and fertilizer for sticky maize. |
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