提高苹果品质并抑制苦痘病发生的钙肥最佳施用量和次数

Optimum application amount and times of calcium nitrate for better fruit quality and lower incidence of apple bitter pit

【目的】探索‘长富2’苹果最佳的补钙措施,有效降低苦痘病的发生,为生产施肥提供理论依据。【方法】以15年生‘长富2’苹果树为试材,进行了土施硝酸钙的田间试验。设钙肥施用量:Ca 0.48、0.72和0.96 kg/株,分别以Ca0.48、Ca0.72和Ca0.96表示;施肥次数设:花前一次施用(1),花前和落花后分两次施用(2),花前、落花后和果实膨大期分3次施用(3),以不施硝酸钙为对照(Ca0),共10个处理。成熟期,测定果实抗氧化酶活性、MDA含量、矿质元素含量、品质以及苦痘病发病率。【结果】与不施钙相比,钙肥处理的果实抗氧化酶SOD、POD和CAT活性均显著提高,MAD含量显著降低(P<0.05),其中,Ca0.72-3处理的3种酶活性又均显著高于其他处理,Ca0.96-3、Ca0.96-2、Ca0.96-1、Ca0.72-2、Ca0.72-1、Ca0.48-2和Ca0.48-3之间差异不明显,但均显著高于Ca0.48-1。钙肥处理果实矿质元素N、P、K、Ca、Mg含量与Ca0差异显著。其中,Ca0.72-2和Ca0.96-1处理果实含氮量较高,显著高于除Ca0.48-1之外的所有处理;磷和钾含量在钙肥施用量和施用次数间没有明显规律;钙和镁含量均以Ca0.72-3处理最高,显著高于其他处理;Ca0.72-3处理的果实单果重(256.67 g)、果形指数(0.86)也均大于其他处理;可溶性固形物含量(13.03%)和总糖含量(11.38%)最高,可滴定酸含量(0.29%)最低,糖酸比(38.81)优于其他处理,苦痘病发病率最低(19%)。【结论】施用硝酸钙肥可显著提高果实中抗氧化酶活性以及钾、钙和镁含量,进而有效降低苦痘病发病率,提高了果实品质。在供试土壤和苹果品种条件下,施用方法以土施硝酸钙0.72 kg/株,在花前、落花后和果实膨大期均分3次施于果树根下的效果最佳。

【Objectives】The suitable application amount and method of calcium fertilizer were studied to find an effective way to reduce the occurrence of bitter pit in apple production.【Methods】A field experiment was conducted using apple cultivar of'Nagafu 2'apple trees(15-year-old)as materials and nitrate calcium as Ca fertilizer.We designed three nitrate calcium rates of 0.48,0.72 and 0.96 kg/plant(Ca0.48,Ca0.72,Ca0.96),and all the three rates were applied in three methods,as:one application before flowering(1),two applications before flowering and after flower falling(2),three applications before flowering,after flower falling and at fruit expanding stage(3),and no calcium application(Ca0)was used as control.At maturing stage,fruit samples were collected for the measurement of antioxidant enzyme activities,MDA content,nutrient element contents,quality and bitter pit incidence.【Results】All the Ca application treatments increased the antioxidant enzyme activities significantly compared with Ca0.The activities of SOD,POD and CAT in Ca0.72-3 were significantly higher than those in all the others;those in Ca0.96-3,Ca0.96-2,Ca0.96-1,Ca0.72-2,Ca0.72-1,Ca0.48-2 and Ca0.48-3 were generally not significantly different with each other,but all significantly higher than those in Ca0.48-1.The N,P,K,Ca and Mg contents of fruit in all the Ca treatments were significantly higher than those in the control.The top two N contents were in Ca0.72-2 and Ca0.96-1,which were significantly higher than those in all the other treatments,except Ca0.48-1.No obvious order was found in P and K contents among treatments;both the highest Ca and Mg contents and the lowest P content were in Ca0.72-3.In treatment Ca0.72-3,the fruit weight,transverse diameter and longitudinal diameter were all significantly higher than those in the others,and the soluble solids and total sugar contents were the highest,the titratable acid content was the lowest(0.29%),with the sugar to acid ratio of 38.81,the incidence of bitter pit was the lowest(19%).【Conclusions】The application of calcium fertilizer could significantly increase the antioxidant enzyme activities and nutrient contents,especially the K,Ca and Mg contents,which are very important for fruit resistance to bitter pit and quality,and the fruit commercial quality.Under the experimental condition,the most satisfactory effect could be obtained by applying calcium nitrate three times in a total amount of Ca 0.72 kg/plant.