季节性干旱下农艺节水措施对甘蔗生长和产量的影响

为探明不同农艺节水措施在甘蔗应对季节性干旱中的作用机制,本研究以‘粤糖94-128’为材料,设置地膜覆盖+有机肥（T1）、保水剂+有机肥（T2）、蔗叶覆盖+有机肥（T3）、蔗叶覆盖+保水剂（T4）4个处理,以常规种植为对照（CK）,研究不同农艺节水处理下土壤水分和出苗率、农艺性状和干物质积累、光合活性和根系指标以及经济性状对季节性干旱的响应。结果表明：干旱胁迫前期土壤含水量表现为地膜覆盖>蔗叶覆盖>无覆盖;T1处理出苗率最高且显著高于CK。2015年,与CK相比,T1处理显著增加株高（18.1%）和+1叶长（30.6%）,T4处理显著增加茎粗（21.8%）,而T2处理的株高、茎粗和叶宽则显著降低;T1处理显著增加+1叶的最大光能利用效率（F_v/F_m）和叶片SPAD值（SPAD-502叶绿素仪测定值）,T3处理显著增加+1叶PSII实际光化学效率（Φ_PSII）,其余各处理与CK之间差异不显著;T1、T2、T3、T4处理的总干物质积累分别增加94.5%、-37.0%、53.4%、79.9%;T3处理显著增加根长密度、根表面积和根数,T2处理各根系指标则显著降低;T2和T3处理单茎重高于T1处理,但有效茎数远低于T1处理,有效茎数高是T1处理高产的主要原因;有机肥处理显著增加田间锤度,T3处理增幅最高。2016年,与CK相比,甘蔗不同处理的农艺性状、生理指标和干物质积累差异不显著;但与2015年相比,T1处理农艺性状指标呈下降趋势,而T2处理则呈上升趋势;各处理+1叶的Φ_PSII均呈下降趋势;T1、T2和T3处理总干物质积累呈下降趋势,而T1和CK则呈上升趋势。T3处理根系生物量和根长密度显著高于CK,主要是由于细根增加所致;T4处理有效茎长显著高于CK,但茎径和单茎重并无显著差异,产量差异源于有效茎数的差异;有机肥处理显著增加田间锤度且各处理的田间锤度与2015年比呈上升趋势。综上,农艺节水措施主要通过在旱季减少土壤水分散失而提高甘蔗出苗率从而增加有效茎数,并通过增加植株干物质积累和促进根系生长以应对季节性干旱,进而保障后期经济性状。

Effect of Agronomic Water Saving Measures on Growth and Yield of Sugarcane under Seasonal Drought

A major objective of this study is to investigate the effects and mechanisms of different agronomic water saving measures on sugarcane confronting seasonal drought. Four treatments including plastic film mulch + organic manure (T1), water retaining agent + organic manure (T2), sugarcane trash mulch + organic manure (T3), sugarcane trash mulch + water retaining agent (T4) and row-planting (CK) were conducted to explore the effects on relative soil water content (RSWC) and emergence rate (ER), root traits and photo-system indices, dry matter accumulation, agronomic and economic characters for tested cultivar ‘YT 94-128’. The results showed that mulch significantly increased RSWC under the early stage of drought, which was plastic film mulch > sugarcane trash mulch > no mulch, ER of T1 was significantly higher than CK. Compared with CK in 2015, the highest plant height (PH), stem diameter (SD), and leaf length (LL) appeared in T1 (18.1%), T4 (30.6%), T1 (21.8%), respectively, but the PH, SD and leaf width (LW) of T2 significantly decreased. F_v/F_m and SPAD significantly increased in T1, +1 leaf PSII quantum efficiency (Φ_PSII) significantly increased in T4, there was no significant difference among the other treatments. Dry matter accumulation for T1, T2, T3 and T4 was 94.5%, -37.0%, 53.4% and 79.9% higher than that of CK. T3 significantly increased the root length density (RLD), root surface area (RSA) and roots, which was opposite to T2. T2 and T3 possessed high single stalk weight (SSW) but the millable stalks (MS) were significantly lower than that of T1, which made T1 the highest yield. In 2016, there were no significant differences for agronomic characters, physiological indies and dry matter production among each treatment comparing with CK. But compared with 2015, the agronomic characters of T1, +1 leaf Φ_PSII of all treatments and dry matter accumulation of T1, T2 and T3 decreased, while the agronomic characters of T2 and dry matter accumulation of T4 and CK increased. The root biomass and root length density of T3 were significantly higher than that of CK, resulted from the increase of fine roots. The result of the difference analysis between MS and yield was consistent.The Br° of T1, T2 and T3 was significantly higher than that of T4 and CK in both 2015 and 2016, reveling that organic manure improved the sugarcane quality. In conclusion, the agronomic water saving measures promoted the emergence rate and formed strong plants via reducing loss of soil moisture, which could increase the millable stalks and dry mater accumulation, and enhance the root system of sugarcane to resist the seasonal drought, which guaranteed the cane yield and quality.