基肥配比和拔节期追氮对糯玉米淀粉胶凝和回生特性的影响

以苏玉糯4号为材料，采用二因素裂区设计，研究了不同基肥配比(纯N 75 kg hm^-2、纯N 75 kg hm^-2+K₂O 70 kg hm^-2、纯N 75 kg hm^-2+P₂O₅ 65 kg hm^-2和纯N 75 kg hm^-2 +P₂O₅ 65 kg hm^-2+K₂O 70 kg hm^-2)和拔节期追氮(0、150和300 kg hm^-2)对糯玉米淀粉胶凝和回生特性的影响。结果表明，淀粉和回生淀粉的起始温度、峰值温度和终值温度虽然受到施肥处理的影响，但总体上变异较小。热焓值受基肥配比影响较小，糊化范围和峰值指数受拔节期追氮量影响较小。在不同基肥配比处理下，糊化范围在基施氮钾时最低，氮磷钾合理配施处理下最高，峰值指数表现和糊化范围相反。在拔节期不同追氮量处理下，热焓值以追氮150 kg hm^-2时最高，追氮300 kg hm^-2或不追氮无显著差异。胶凝淀粉冷藏后发生回生，表现为转变温度、热焓值和峰值指数降低，糊化范围变宽。和仅基施氮相比，增施磷或(和)钾都可降低淀粉的回生值和回生淀粉的热焓值，拔节期追氮处理的这两项指标均劣于不追氮处理。回生值与回生淀粉的热焓值和峰值指数显著正相关，相关系数分别为0.90 (P < 0.01)和0.41 (P < 0.05); 原淀粉的热焓值与峰值指数极显著正相关, 相关系数为0.65 (P < 0.01)，与回生淀粉热焓值显著正相关，相关系数0.44 (P < 0.05)，与终值温度显著负相关，相关系数-0.41 (P < 0.05)。在本试验条件下，以氮磷钾均衡基施并拔节期追氮150 kg hm^-2时，淀粉胶凝和回生特性较为理想，表现为热焓值较高，回生值较低。

Starch Gelatinization and Retrogradation Properties under Different Basic Fertilizer Regimes and Nitrogen Topdressing at Jointing Stage of Waxy Maize

Proper fertilizer managements can improve the starch gelatinization and retrogradation properties of waxy maize (Zea mays L. Ceratina Kulesh). The split-design experiment was conducted using waxy maize cultivar Suyunuo 4 with four main plots subjected to basal fertilizer treatments of N 75 kg ha^-1, N 75 kg ha^-1+K₂O 70 kg ha^-1, N 75 kg ha^-1+P₂O₅ 65 kg ha^-1, and N 75 kg ha^-1+P₂O₅ 65 kg ha^-1+K₂O 70 kg ha^-1, respectively in 2007 and 2008. The three split plots were topdressed with nitrogen of 0, 150, and 300 kg ha^-1 at jointing stage, respectively. Though onset temperature (T_o), peak temperature (T_p) and conclusion temperature (T_c) of native starch and retrogradated starch were affected by fertilizer treatments, the variation was little. No significant effects were observed for basic fertilizer treatments on the enthalpy of gelatinization (ΔH_gel), and for N topdressing treatments on gelatinization range (R) and peak height index (PHI). The R-value was the lowest in the treatment with only N and K in basal fertilizer, and the highest in the treatment with N, P, and K in basal fertilizer. The changes of PHI showed an opposite trend to R. The ΔH_gel was the highest in the treatment with medium N topdressing (150 kg ha^-1). Gelatinized starch became retrograded with lower T_o, T_p, T_c, enthalpy of retrogradation (ΔH_ret), and PHI, as well as wider R. Compared with the treatment of only N applied in basal fertilizer, the percentage of retrogradation and ΔH_ret decreased when P and/or K added in the basal fertilizer. The two indicators were higher in the treatments with N topdressing than without N topdressing. The percentage of retrogradation was positively correlated with ΔH_ret (r = 0.90, P < 0.01) and PHI of retrograded starch (r = 0.41, P < 0.05). ΔH_gel was positively correlated with PHI (r = 0.65, P < 0.01) and ΔHret (r = 0.44, P < 0.05), but negatively correlated with T_c (r = -0.41, P < 0.05). It is recommended to apply balanced fertilization with N, P, and K combining with moderate N topdressing under conditions similar to the experiment to improve gelatinization and retrogradation properties of waxy maize starch.