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陕北高原地区土地资源丰富,光照充足、昼夜温差大,属于干旱半干旱大陆性季风气候,具有北方旱寒区典型的气候特点。干旱、寒冷,冬季极端温度可达−20℃ 以下,年降水量500 mm左右, 降雨量少且年度分布不均,冬春干旱而秋季多雨。当地土壤类型主要是黄绵土,土层深厚,土壤中的矿质养分含量低,耕地土壤有机质含量不足1%,土壤板结、通气透水性能较低,土壤肥力和质量均较差[1]。
陕北半干旱地区是世界公认的苹果最优适生区,苹果品质优良、种植面积巨大,仅陕北苹果种植面积已超过20万hm2。陕北果园苹果旺盛生长季土壤相对含水量大多小于60%,季节性干旱严重,0—60 cm土层贮水量与降水量的变化一致;果树根区0—200 cm土层水分普遍亏欠[2]。陕北地区20年以上果园降雨向深层土壤的下渗接近于零,不同树龄的果园2.0—4.0 m土层以下均出现严重或强烈干化;干土层切断了深层水分与上层的联系,形成了土壤−植物−大气的异常土壤水分循环模式[3−5]。研究发现,地膜(包括黑膜和透明膜)覆盖、秸秆覆盖、砂石覆盖均显著降低土壤水分蒸发,提高土壤蓄水量和水分利用效率,显著促进作物根系生长,提高作物产量[6−7]。进一步的研究还发现,砂石覆盖和地膜覆盖显著提高土壤温度,而秸秆覆盖可有效降低土壤温度,抵御夏季高温对作物的伤害,并可增加土壤孔隙度,增加土壤有机质含量,促进土壤细菌的繁殖和代谢,建立良性的土壤生态系统[8−10]。显然,黄土高原苹果产量及品质主要受限于当年降雨和土壤肥力,而采取适宜的覆盖措施可有效抑制土壤蒸发,增加雨水下渗和土壤水储量,控制和减缓深层土壤干燥,培肥土壤,提高苹果产量和品质。
油菜是一年生养地作物,具有较强的适应性和抗逆性,耐寒、耐旱,对土壤肥力要求不高,坡地、低洼地都可很好地生长。油菜春、夏、秋3季都可播种,生长迅速,地上生物量大,地下根系较浅,不会像多年生牧草那样在土壤中形成密集厚实的根系层,避免和果树争水争肥。油菜植株中植物所需营养元素含量丰富,油菜干草含氮量(N)可达到2.52%,含磷量(P2O5) 1.53%[11],近年来油菜作为绿肥和养地作物被广泛种植。本研究针对黄土高原果园春季干旱缺水、土壤瘠薄以及其恶劣的生态环境,利用当地秋季多雨的气候特点,选择宜作绿肥的油菜品种于夏末秋初套种于苹果园行间,秋末割倒油菜地上部分覆盖于果树根区,抑制土壤蒸发,“秋水春用”以缓解春季土壤干旱,培肥土壤,提高苹果产量和质量。
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试验地位于陕西省延安市宝塔区河庄坪镇余家沟村(36°11′~37°09′N,109°21′~110°03′E),海拔1100 m;年平均降雨量500 mm左右,雨量集中在7—10月份,冬春干旱。年均气温9.4℃,无霜期170~186天。土壤类型为黄绵土,土质疏松,土层深厚,土壤容重 1.28 g/cm3,田间持水量为20%;土壤瘠薄,有机质含量0.3%左右。试验地位于丘陵沟壑区台田上地势平坦的山地果园内,苹果主栽品种为雨养红富士 (Malus pumila Mill.),八棱海棠作砧木,种植密度为5 m×4 m,树龄2年。
绿肥油菜品种筛选试验(2019年8月—2020年4月): 选择不同类型油菜品种,即天油10号 (V1)、延油2号 (V2)、天油7号 (V3)、陇油8号 (V4)、09鉴8 (V5)、浩油11 (V6)、2002 (V7)、春陕2B (V8)、1721-1B (V9)、秦优7号 (V10)。其中V1~V5为白菜型 (Brassica campestris L.) 冬性油菜品种,V6为白菜型 (Brassica campestris L.) 春性油菜品种,V7~V10为甘蓝型 (Brassica napus L.) 冬性油菜品种。油菜播种行距果树主杆1.15 m,油菜行距0.30 m,株距0.10 m, 种植密度约33万株/hm2。2019年8月1日—8月10日趁雨播种,8月17日前后齐苗。统一耕作,统一施肥管理,全程无灌溉,记载各油菜品种生长情况。10月30日前割倒油菜地上部分并苫盖于邻近果树根区之上,以行间未套种油菜、果树根盘未覆盖的清耕(CK)作为对照。每个油菜品种重复3个小区,每次重复内各油菜品种随机排列,小区面积100m2 (5.0 m×20.0 m)。
2年定点覆盖试验 (2020年8月—2022年10月),2020、2021年秋季分别将甘蓝型油菜品种V9、V10套种于果树行间,秋末割倒地上部分,分别苫盖于邻近果树根区,即处理:覆盖-V9、覆盖-V10;分别以清耕空白作为对照,即清耕-V9、清耕-V10。每个处理设3个重复。播种时间、覆盖时间、覆盖方法、小区面积、田间管理同上。
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油菜还田前每小区选取生长均匀有代表性的区域,用0.8 m×1.0 m取样框取样,刈割油菜地上部分,60℃烘干 (105℃杀青30 min) 称重,换算为地上生物学产量,3次重复。
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品种筛选试验翌年3月 (2020年3月)、定点覆盖试验第2年油菜生长旺盛期 (2021年10月中旬)、翌年 (2022年) 3和5月份中下旬,用土钻分层取0—20、20—40、40—60 cm土层的土壤、或者取0—25、25—50、50—75、75—100、100—125、125—150、150—175 cm土层的土壤,装入铝盒,105℃烘干、称重,测量土壤水分含量,3次重复。
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定点覆盖试验进行两年后(2022年10月),每小区选择3株果树,称重每株果树苹果产量,以平均值计为单株苹果产量;单果重采用称重法,单果直径采用游标卡尺测量,每小区10次重复,计算平均值。
采用高效液相色谱法(GB5009.86—2016)测定苹果维生素C含量,采用酸碱滴定指示剂法 (GB/T12456—2008) 测定总酸含量,采用3、5-二硝基水杨酸比色法(NY/T2742—2015)测定可溶性总糖含量,采用折射仪法 (NY/T2637—2014) 测定可溶性固形物含量。
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定点覆盖试验进行2年后 (2022年8月),采集耕层0—20 cm的土壤,测定土壤养分含量。采用硫酸消解—凯氏定氮法测定土壤全氮含量,采用硫酸高氯酸消解—钼锑抗比色法测定土壤全磷含量,采用碳酸氢钠浸提—钼锑抗比色法测定土壤有效磷含量,采用醋酸铵浸提—火焰光度计法测定土壤速效钾含量,采用碱解扩散法测定碱解氮含量,采用重铬酸钾外加热法测定有机质含量。
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试验数据处理及图表制作采用Excel 2010和DPS V7.55分析软件。采用相关分析法计算相关系数,方差分析采用Duncan新复极差法。
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果树根区覆盖油菜后的翌年3月,与清耕(CK)对照相比,白菜型春性品种V6、甘蓝型品种V9、V10的覆盖处理显著增加0—20、20—40、40—60 cm土层土壤水分含量 (P<0.05);甘蓝型品种V7、V8处理显著增加0—20 cm土壤水分含量 (P<0.05);白菜型冬性品种V1、V2、V3、V4处理0—20、20—40、40—60 cm土层的土壤水分含量与对照相比无显著变化,V5处理仅使0—20 cm土壤水分含量显著增加 (图1)。显然,与对照相比,白菜型冬性品种覆盖保墒效果不显著,白菜型春性品种和甘蓝型冬性品种覆盖可显著增加翌年3月份0—60或0—20 cm土壤水分含量。
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如表1所示,参试油菜品种秋季地上生物学产量表现为:V10>V6>V9>V4>V8>V3>V1>V2>V7>V5,白菜型春性品种V6和甘蓝型冬性品种V9、V10的地上生物学产量显著大于白菜型冬性品种V1、V2、V3和V5。秋末以油菜地上部分覆盖果树根区,翌年3月果树根区20—40 cm土层土壤水分含量与油菜地上生物学产量显著正相关 (P<0.05),40—60 cm土壤水分含量与油菜地上部分生物学产量极显著正相关 (P<0.01)。即油菜覆盖处理下,秋季油菜地上生物学产量(即覆草量)与翌年3月20—60 cm土层土壤水分含量显著正相关。
表 1 果树根区土壤水分含量与油菜地上部生物量的相关系数
Table 1. Correlation coefficients between soil water contents around fruit tree root area and the aboveground biomass of rapeseed
品种
Variety生物量 (kg/hm2)
Biomass相关系数 Correlation coefficient C1 × Y C2 × Y C3 × Y V1 4901±95.1 e 0.52 0.73* 0.82** V2 4400±166.9 f V3 4974±64.0 e V4 5507±176.2 cd V5 3594±259.1 g V6 6502±230.9 b V7 3878±145.3 g V8 5302±260.6 de V9 5790±143.6 c V10 6973±620.8 a 注:V1~V5为白菜型冬性油菜品种,V6为白菜型春性油菜品种,V7~V10为甘蓝型冬性油菜品种。Y―10月下旬油菜地上部生物量,C1、C2、C3分别为翌年3月份果树根区0—20、20—40、40—60 cm土层土壤水分含量。同列数据后不同小写字母表示品种间差异达0.05 显著水平。*、**分别表示油菜生物量与土壤水分含量在0.05、0.01水平相关显著。
Note: V1−V5 are the Brassica campestris L. winter varieties, V6 is the Brassica campestris L. spring variety, and V7−V10 are the Brassica napus L. winter varieties. Y is aboveground biomass of rapeseed variety in late October. C1, C2, and C3 represent water content in 0−20, 20−40 and 40−60 cm soil depth in fruit tree root area in the following March, respectively. The different lowercase letters after data in a column indicate significant difference among rapeseed varieties (P<0.05). * and ** indicate the correlation between rapeseed biomass and soil water content at 0.05 and 0.01 significant levels, respectively. -
两年定点覆盖试验中,油菜品种V9、V10生长季(2021年10月)果树行间0—25、25—50 cm土层土壤水分含量显著低于清耕对照,而50 cm以下(不包含50 cm)各土层土壤水分含量无显著差异 (图2A、2B);果树根区各土层土壤水分含量与清耕对照相比均无显著差异 (图2C、2D)。虽然油菜生长季节 (秋季) 显著降低了果树行间0—50 cm土层土壤水分含量,但对邻近果树根区土壤水分含量无显著影响。
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由图3可知,在覆盖试验实施2年后,3月份V9覆盖处理 0—150 cm各土层土壤水分含量比清耕对照显著增加了16.6%~30.0%,平均增加了21.8%,V10覆盖处理各层土壤水分含量增加了4.8%~25.9%,平均增加了17.6% (P<0.05)。5月份V9 覆盖处理0—125 cm各土层土壤水分含量比清耕对照显著增加了8.2%~17.9%,平均增加了12.5%,V10处理0—100 cm各土层土壤水分含量显著增加了7.2%~39.9%,平均增加了21.6% (P<0.05)。总之,两个油菜品种V9、V10地上部分秋末刈割后覆盖在果树根区,显著增加了来年果树根区3月份0—150 cm、5月份0—100 cm土层的土壤水分含量。
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与清耕对照相比 (表2),V9、V10连续2年秋末覆盖果树根区处理土壤有效磷含量分别显著增加32.2%、44.9% (P<0.05),速效钾含量分别显著增加146.4%、95.4% (P<0.05),全氮含量分别显著增加25.2%、25.6% (P<0.05),有机质含量分别显著增加23.8%、37.7% (P<0.05)。V10覆盖处理显著增加土壤全磷含量11.8% (P<0.05),碱解氮含量显著增加62.7% (P<0.05)。连续2年油菜覆盖处理显著增加耕层土壤有效磷、速效钾、全氮和有机质含量,土壤全磷含量呈现增加趋势。
表 2 连续两年油菜覆盖和清耕处理下果树根区土壤养分含量
Table 2. Soil fertility in fruit tree root area under two years’ mulching and clear tillage treatments
处理 Treatment 有效磷
Available P
(mg/kg)速效钾
Available K
(mg/kg)碱解氮
Available N
(mg/kg)全氮
Total N
(mg/kg)全磷
Total P
(mg/kg)有机质
Organic matter
(g/kg)覆盖-V9 Mulching-V9 10.93±1.021 a 252.6±24.85 a 10.51±1.520 a 281.1±18.11 a 621.2±27.77 a 4.73±0.323 a 清耕-V9 Clear tillage-V9 8.27±0.322 b 102.5±11.23 b 10.92±0.923 a 224.6±22.10 b 569.1±26.92 a 3.82±0.240 b 覆盖-V10 Mulching-V10 15.07±1.443 a 242.9±27.73 a 14.19±0.950 a 277.1±1.99 a 642.9±20.76 a 5.33±0.620 a 清耕-V10 Clear tillage-V10 10.40±0.656 b 124.3±21.41 b 8.72±1.072 b 220.6±24.80 b 574.9±27.45 b 3.87±0.493 b 注:V9、V10代表两个甘蓝型冬性油菜品种。同列数据后不同小写字母表示覆盖与清耕处理间差异显著 (P<0.05)。
Note: The V9、V10 are two Brassica napus L. winter varieties. Different lowercase letters after data in a column indicate significant difference between mulching and clear tillage (P<0.05). -
与清耕对照相比,V9连续2年覆盖处理对单果直径和单果重及总糖含量的增加幅度不显著,但苹果产量显著增加了5.81 kg/株,V10连续覆盖显著提高了单果直径、单果重和单株产量及总糖含量 (P<0.05)。V9、V10覆盖处理均显著降低果实总酸含量,增加维生素C含量,对可溶性固形物含量的影响不显著 (表3)。总之,甘蓝型冬性油菜秋末覆盖果树根区可显著增加苹果产量,改善果实品质。
表 3 油菜覆盖对苹果产量及品质的影响
Table 3. Effect of the rapeseed mulching on apple yield and quality
处理
Treatment单果直径
Fruit diameter
(mm)单果重
Single fruit weight
(g)单株产量
Apple yield
(kg/tree)维生素C
Vitamin C
(mg/kg)可溶性固形物
Soluble solid
(%)总酸
Total acids
(g/kg)总糖
Total sugar
(g/kg)覆盖-V9
Mulching-V984.56±2.011 a 241.5±7.851 a 13.79±1.686 a 23.31±0.710 a 14.29±0.873 a 2.93±0.070 b 137.1±4.402 a 清耕-V9
Cclear tillage-V983.45±2.006 a 230.6±2.865 a 7.98±0.833 b 21.40±0.516 b 14.53±0.603 a 3.23±0.038 a 133.3±4.723 a 覆盖-V10
Mulching-V1086.83±0.319 a 240.0±4.466 a 8.84±0.664 a 20.77±0.290 a 13.74±0.234 a 3.03±0.154 b 127.4±2.804 a 清耕-V10
Clear tillage-V1085.01±0.521 b 228.8±1.61 b 7.51±0.418 b 18.65±0.150 b 13.20±0.971 a 3.70±0.185 a 118.5±4.650 b 注:V9、V10代表两个甘蓝型冬性油菜品种。同列数据后不同小写字母表示覆盖与清耕处理间差异显著 (P<0.05)。
Note: The V9、V10 are two Brassica napus L. winter varieties. Different lowercase letters after data in a column indicate significant difference between mulching and clear tillage (P<0.05). -
一般来讲,绿肥种植期间不同程度地降低土壤水分含量[12−16]。黄土高原沟壑区土壤水分的蓄积主要发生在7月至10月中旬,3—6月份季节性干旱明显[17],干旱季节当地果园土壤水分亏缺度高达18.5%~47.5%[18]。因而该地区果园常通过地面覆盖来保持土壤墒情,增加土壤水分含量,覆盖材料包括了麦草、稻草帘、玉米秸秆、砾石、黑膜、白膜、生草等[19−21]。然而,这些覆盖物对果树生长和结果有不同程度的不利影响,如果树行间种植玉米等高秆作物会造成果树遮光,麦秸、稻秸等在黄土高原地区较短缺,地膜覆盖后不利于果树施肥、灌水等耕作,增加环境污染,且薄膜覆盖还会加重夏季高温对树根生长的影响;秸秆覆盖不仅显著增加了土壤水分贮存,且可调节耕层土壤温度[19]。但较厚的地面秸秆覆盖在一定程度上会减少降雨向土壤中的渗透[22]。本研究结合黄土沟壑区秋季多雨的气候特点,夏末秋初在果树行间套种生物量较大的白菜型春性和甘蓝型冬性油菜品种,秋末刈割覆盖于果树根区,显著增加了翌年3月份果树根区0—60或0—20 cm土壤水分含量,且土壤水分含量与油菜地上部分生物学产量显著正相关。本研究还发现,由于黄土高原地区雨热同季,秋季雨量较多,果树行间套种甘蓝型冬性油菜,其盛长期降雨较多,因而油菜生长主要消耗0—50 cm土壤水分,对50 cm以下土层土壤水分及邻近果树根区土壤水分无显著的竞争性消耗;秋末用此油菜覆盖果树根区,连续进行2年后,春季0—150 cm (3月)和0—100 cm (5月)土壤水分含量显著增加,实现“秋水春用”。
许多研究证实,秸秆覆盖和绿肥还田可有效增加土壤有机质、全氮、碱解氮、速效磷含量,降低土壤容重和pH,促进土壤微生物的代谢和土壤细菌的繁殖,土壤脲酶、酸性磷酸酶、蔗糖酶、过氧化氢酶等活性显著提高[10, 23−26]。油菜植株养分含量丰富,水分含量高,易腐解,其腐烂过程中产生的有机酸可以调整土壤pH,促进土壤中难溶性养分的释放,将油菜作绿肥翻压,可显著增加土壤有机质及土壤N、P、K等的含量,增加土壤毛管孔隙度,抑制病原菌,显著提高早稻及后茬稻产量[11, 27−28]。本研究连续两年以油菜绿肥秋末覆盖果树根区,显著增加了耕层土壤有效磷、速效钾、全氮和有机质含量。
采用地面覆盖技术,增加土壤贮水量,可显著增加农作物产量[29−32]。干旱缺水和土壤瘠薄严重影响黄土高原苹果的产量和品质,改善果园土壤水分状况、缓解深层土壤干燥化,可显著提高单果重、苹果产量及优果率[6, 33−34]。苹果一般在9、10月份进入成熟期,对水分、养分需求较少,在果实生长后期适当控水能提高酸转化酶活性,增加苹果可溶性糖含量及可溶性物质总量,降低滴定酸含量,改善品质且不会影响单果重量[35]。这也解释了为什么本研究通过秋季果园套种和覆盖油菜,不仅改善了土壤的水肥条件,而且提高了苹果的产量和品质。
有研究结果显示,在黄土高原半干旱地区种植、覆盖黄豆秸秆,相对于聚乙烯薄膜覆盖和不覆盖增加净收入,且避免了薄膜覆盖带来的环境污染[36]。半干旱地区果园很容易滋生多年生杂草并形成致密的根系层,特别在雨热同季(5—10月份)杂草生长更加茂盛,与果树争肥争水;因此常规栽培条件下,每年需要多次清除果园杂草,增加栽培成本。显然,本研究在高温高湿季节(7—10月份)在陕北果园套种和覆盖一年生油菜绿肥,不仅显著提高苹果产量和品质,还可有效清除和抑制杂草生长,节省成本,增加收入,减少环境污染,当然,这有待进一步深入研究。
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地上生物学产量较大的白菜型春性和甘蓝型冬性油菜秋季套种于果园不会与果树争水,秋末油菜覆盖果树根区可显著增加翌年3月份土壤水分含量,且20—60 cm土层土壤水分含量与油菜地上生物学产量(覆草量)显著正相关。甘蓝型冬油菜秋季覆盖果树根区连续实施两年后,分别显著增加翌年3、5月份0—150、0—100 cm土壤水分含量,显著增加耕层土壤有效磷、速效钾、全氮及有机质含量;显著提高苹果产量,果品总酸含量显著降低,维生素C含量显著增加,总糖含量增加。总之,地上生物学产量较高的白菜型(Brassica campestris L.)春性和甘蓝型(Brassica napus L.)冬性油菜适宜于黄土高原果园秋季套种和覆盖,油菜覆盖能有效保墒蓄水,培肥土壤,提高苹果产量,改善苹果营养品质。
陕北黄土高原果园覆盖绿肥油菜的品种筛选及其水肥效应
Variety screening of greening manure rapeseed and the mulching effect on soil moisture conservation and fertility in dryland orchard of Loess Plateau
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摘要:
【目的】 干旱少雨和土壤瘠薄是陕北苹果生产中存在的主要问题。研究不同绿肥油菜品种覆盖还田在缓解果园春季干旱、培肥土壤及提高苹果产量和质量方面的效应,为陕北苹果生产提供理论基础。 【方法】 试验位于陕西省延安市河庄坪镇的山地果园,供试果树品种为红富士(Malus pumila Mill.),树龄2年。首先进行了绿肥油菜品种筛选试验,供试品种包括5个白菜型冬油菜(Brassica campestris L.)品种 (V1~V5)、1个白菜型春油菜(Brassica campestris L.)品种(V6)、4个甘蓝型冬油菜(Brassica napus L.)品种(V7~V10)。油菜于2019年8月初在果园行间套种,10月30日前刈割地上部分,覆盖于邻近果树根区(根周围半径0—115 cm范围),2020年3月测定果树根区0—60 cm深土壤水分含量,发现V9和V10的覆盖保墒效果较好,用于后续的两年定点覆盖试验。2020—2022年定点试验的油菜套种、覆盖方法同品种筛选试验,于覆盖试验第二年油菜生长季节(2021年10月)测定果树行间和根区0—175 cm土层水分含量,2022年3月、5月份测定果树根区0—175 cm土层水分含量,8月份测定0—20 cm土层养分含量,收获期测定苹果产量和质量。 【结果】 1)品种筛选试验,白菜型冬性油菜品种V1、V2、V3和V4覆盖处理对0—60 cm土层水分含量均无显著影响,V5覆盖处理仅显著增加0—20 cm土层水分含量;而白菜型春性品种V6和甘蓝型冬性品种V7、V8、V9和V10覆盖处理显著增加0—20或0—60 cm土层水分含量;品种V6、V9和V10秋季地上生物学产量显著大于品种V1、V2、V3和V5。油菜地上部生物量 (覆草量) 与翌年3月份20—40、40—60 cm土层水分含量显著正相关。2)两年定点试验,在油菜生长季,两个品种V9、V10均显著降低了果树行间0—50 cm土层水分含量,对根区土壤水分无显著影响;2022年3月份根区0—150 cm土层水分含量显著增加17.6%~21.8%,5月份根区0—100 cm土层水分含量显著增加12.5%~21.6%,0—20 cm土层土壤有效磷、速效钾、全氮、有机质含量分别显著增加32.2%~44.9%、95.4%~146.4%、25.2%~25.6%、23.8%~37.7%。单株苹果产量和单果重增加;苹果维生素C含量显著增加,总酸含量显著降低,总糖含量增加。 【结论】 在陕北高原地区,秋季果园套种油菜并在秋末刈割覆盖于果树根区,可显著提高来年春季果树根区0—100 cm土壤水分含量,培肥土壤,增加苹果产量,改善苹果营养品质。覆盖效果取决于油菜地上部生物量。在陕北高原地区,生产上建议选择地上生物学产量较高的白菜型(Brassica campestris L.)春性和甘蓝型(Brassica napus L.)冬性油菜品种进行果园套种及覆盖。 Abstract:【Objectives】 Drought and poor soil fertility restrict the apple production benefit in the semi-arid area of Loess Plateau. We screened suitable rapeseed varieties as green manure, and studied their mulching effect in improving soil moisture in spring and soil fertility. 【Methods】 The experiment was carried out in a hilly apple orchard in Yan’an City, Shaanxi Province, where the rainfall was rare in winter and spring, and mainly happen from July to October of a year. Firstly, rapeseed varieties were screened for water conservation effect, including five Brassica campestris L. winter varieties (V1−V5), one Brassica campestris L. spring variety (V6), and four Brassica napus L. winter varieties (V7−V10). The rapeseeds were sown in unplanted land between apple tree lines in early August 2019, and the aboveground part were mown by the end of October and mulched on nearby root area of apple tree (0−115 cm radius around tree trunk). The water contents in 0−60 cm soil depth in the root area were measured in the following March. The rapeseed varieties V9 and V10 showed better water conservation effect than the other ones, so were chosen as the test materials for the following two years position mulching experiment (2020−2022), in which the rapeseed sowing, mowing, and mulching were the same as in the variety screening experiment. In rapeseed growing season (in October 2021), the soil water contents in 0−175 cm soil layer in both rapeseed planting area and apple tree root area were measured. After autumn mulching of rapeseed plant, soil in 0−175 cm soil layer in the mulched root area of apple tree was sampled in March and May 2022 for the measurement of water contents, and the 0−20 cm soil was sampled on August for nutrient measurement. At harvest season, the apple yield and quality were measured. 【Results】 1) Screening of rapeseed variety: The mulching of rapeseed variety V1, V2, V3, and V4 did not show water conservation effect, the V5 mulching only increased water content in 0−20 cm soil layer. The V6, V7, V8, V9 and V10 mulching significantly increased 0−20 or 0−60 cm soil water content. The V6, V9 and V10 were recorded significantly higher aboveground biomass than the V1, V2, V3, and V5. The water contents in 20−40 and 40−60 cm soil layers were positively (P<0.05) correlated with the mulching amount of rapeseed plants. 2) Mulching position experiment: Rapeseed planting decreased water contents in 0−50 cm soil layer in their growing season (P<0.05), and did not influence that in root area soil of apple tree. In the second year (2022) of continuous mulching, the water contents in 0−150 cm depth of root area soil of apple tree were increased by 17.6%−21.8% in March, and those in the 0−100 cm soil layer were increased by 12.5%−21.6% in May; the contents of available P, available K, total N, and organic matter in the 0−20 cm soil were significantly increased by 32.2%−44.9%, 95.4%−146.4%, 25.2%−25.6%, and 23.8%−37.7%, respectively. The rapeseed mulching significantly improved the fruit yield per tree and single fruit weight, and increased apple vitamin C content, total sugar content and decreased total acid content. 【Conclusions】 Interplanting of rapeseeds in autumn and mulching with the aboveground shoots around root area soil of apple tree showed significant soil water conservation and fertility promotion effect, resulting in satisfactory yield and quality effect on apple fruit. As the mulching effect is correlated to the biomass of rapeseed shoots, Brassica campestris L. spring variety and Brassica napus L. winter variety are recommended as the mulching green manure of apple orchards. -
Key words:
- Loess Plateau /
- apple orchard /
- rapeseed variety /
- mulching /
- drought /
- soil fertility
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表 1 果树根区土壤水分含量与油菜地上部生物量的相关系数
Table 1. Correlation coefficients between soil water contents around fruit tree root area and the aboveground biomass of rapeseed
品种
Variety生物量 (kg/hm2)
Biomass相关系数 Correlation coefficient C1 × Y C2 × Y C3 × Y V1 4901±95.1 e 0.52 0.73* 0.82** V2 4400±166.9 f V3 4974±64.0 e V4 5507±176.2 cd V5 3594±259.1 g V6 6502±230.9 b V7 3878±145.3 g V8 5302±260.6 de V9 5790±143.6 c V10 6973±620.8 a 注:V1~V5为白菜型冬性油菜品种,V6为白菜型春性油菜品种,V7~V10为甘蓝型冬性油菜品种。Y―10月下旬油菜地上部生物量,C1、C2、C3分别为翌年3月份果树根区0—20、20—40、40—60 cm土层土壤水分含量。同列数据后不同小写字母表示品种间差异达0.05 显著水平。*、**分别表示油菜生物量与土壤水分含量在0.05、0.01水平相关显著。
Note: V1−V5 are the Brassica campestris L. winter varieties, V6 is the Brassica campestris L. spring variety, and V7−V10 are the Brassica napus L. winter varieties. Y is aboveground biomass of rapeseed variety in late October. C1, C2, and C3 represent water content in 0−20, 20−40 and 40−60 cm soil depth in fruit tree root area in the following March, respectively. The different lowercase letters after data in a column indicate significant difference among rapeseed varieties (P<0.05). * and ** indicate the correlation between rapeseed biomass and soil water content at 0.05 and 0.01 significant levels, respectively.表 2 连续两年油菜覆盖和清耕处理下果树根区土壤养分含量
Table 2. Soil fertility in fruit tree root area under two years’ mulching and clear tillage treatments
处理 Treatment 有效磷
Available P
(mg/kg)速效钾
Available K
(mg/kg)碱解氮
Available N
(mg/kg)全氮
Total N
(mg/kg)全磷
Total P
(mg/kg)有机质
Organic matter
(g/kg)覆盖-V9 Mulching-V9 10.93±1.021 a 252.6±24.85 a 10.51±1.520 a 281.1±18.11 a 621.2±27.77 a 4.73±0.323 a 清耕-V9 Clear tillage-V9 8.27±0.322 b 102.5±11.23 b 10.92±0.923 a 224.6±22.10 b 569.1±26.92 a 3.82±0.240 b 覆盖-V10 Mulching-V10 15.07±1.443 a 242.9±27.73 a 14.19±0.950 a 277.1±1.99 a 642.9±20.76 a 5.33±0.620 a 清耕-V10 Clear tillage-V10 10.40±0.656 b 124.3±21.41 b 8.72±1.072 b 220.6±24.80 b 574.9±27.45 b 3.87±0.493 b 注:V9、V10代表两个甘蓝型冬性油菜品种。同列数据后不同小写字母表示覆盖与清耕处理间差异显著 (P<0.05)。
Note: The V9、V10 are two Brassica napus L. winter varieties. Different lowercase letters after data in a column indicate significant difference between mulching and clear tillage (P<0.05).表 3 油菜覆盖对苹果产量及品质的影响
Table 3. Effect of the rapeseed mulching on apple yield and quality
处理
Treatment单果直径
Fruit diameter
(mm)单果重
Single fruit weight
(g)单株产量
Apple yield
(kg/tree)维生素C
Vitamin C
(mg/kg)可溶性固形物
Soluble solid
(%)总酸
Total acids
(g/kg)总糖
Total sugar
(g/kg)覆盖-V9
Mulching-V984.56±2.011 a 241.5±7.851 a 13.79±1.686 a 23.31±0.710 a 14.29±0.873 a 2.93±0.070 b 137.1±4.402 a 清耕-V9
Cclear tillage-V983.45±2.006 a 230.6±2.865 a 7.98±0.833 b 21.40±0.516 b 14.53±0.603 a 3.23±0.038 a 133.3±4.723 a 覆盖-V10
Mulching-V1086.83±0.319 a 240.0±4.466 a 8.84±0.664 a 20.77±0.290 a 13.74±0.234 a 3.03±0.154 b 127.4±2.804 a 清耕-V10
Clear tillage-V1085.01±0.521 b 228.8±1.61 b 7.51±0.418 b 18.65±0.150 b 13.20±0.971 a 3.70±0.185 a 118.5±4.650 b 注:V9、V10代表两个甘蓝型冬性油菜品种。同列数据后不同小写字母表示覆盖与清耕处理间差异显著 (P<0.05)。
Note: The V9、V10 are two Brassica napus L. winter varieties. Different lowercase letters after data in a column indicate significant difference between mulching and clear tillage (P<0.05). -
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