青贮玉米适收期淀粉、干物质含量和果穗鲜质量占比关系研究

Study on the Relationship Between the Content of Starch and Dry Matter,the Ratio of Fresh Weight of Ear in Silage Maize

青贮玉米的产量和品质与收获期密切相关,探究并明确优质青贮玉米品种在适收期(籽粒乳线位置1/2时)的淀粉、干物质含量和果穗鲜质量占比等指标,为青贮玉米生产适期收获和优质高产品种选择提供重要参考和依据。试验于2018-2019年在北京市农林科学院通州试验基地进行,累计选用40个优质专用型和粮饲兼用型青贮玉米品种,在籽粒乳线位置1/2时取样,各小区分别取5株,称取全株各器官茎、叶、鞘、果穗(不带苞叶)、苞叶、穗轴和籽粒的鲜质量;将玉米全株和籽粒105℃下杀青30 min后,60℃烘干至恒质量,称取干质量后磨样测全株淀粉含量。结果表明:籽粒乳线位置1/2时,参试青贮玉米品种的果穗鲜质量(不带苞叶)与全株鲜质量的比例(全文简称果穗鲜质量占比)、籽粒鲜质量与全株鲜质量的比例(全文简称籽粒鲜质量占比)、籽粒干质量与全株干质量的比例(全文简称籽粒干质量占比)在不同青贮类型和品种间均存在显著差异。参试品种果穗鲜质量占比平均为30.2%(变幅25.5%~35.7%),籽粒鲜质量占比平均为20.9%(变幅16.2%~26.4%),籽粒干质量占比平均为41.1%(变幅33.6%~48.0%)。粮饲兼用型玉米品种的果穗鲜质量、籽粒鲜质量占比和籽粒干质量占比分别较青贮专用型品种高1.5,3.8,5.6百分点。参试品种的全株含水率平均为68.8%,变幅63.1%~73.6%,其中专用型青贮玉米品种平均为70.1%,粮饲兼用型玉米品种平均为67.3%;参试品种的籽粒含水率平均为39.0%,变幅35.4%~43.6%,其中专用型青贮玉米品种平均为39.6%,粮饲兼用型玉米品种平均为38.3%。两类青贮玉米品种的全株含水率和籽粒含水率相当。参试品种的全株淀粉含量平均为30.9%(变幅25.3%~35.6%),其中专用型青贮品种中京科青贮368淀粉含量(32.9%)最高、大京九23(25.3%)最低;粮饲兼用型品种中以京科968(35.6%)和京农科728(35.6%)最高,MC859(28.3%)最低。不同类型青贮品种间,专用型青贮品种全株淀粉含量平均为29.6%,较粮饲兼用型品种(32.5%)低2.9百分点。籽粒乳线位置1/2时,参试青贮玉米品种平均全株含水率和籽粒含水率分别为68.8%,39.0%,平均全株淀粉含量为30.9%;平均果穗鲜质量占比、籽粒鲜质量占比和籽粒干质量占比分别为30.2%,20.9%,41.1%。为此,提出在适收期内专用型/粮饲兼用型青贮玉米品种的果穗鲜质量占比≥30%(籽粒鲜质量占比≥20%、籽粒干质量占比≥40%),此时青贮玉米干物质含量≥30%、淀粉含量≥30%,果穗鲜质量占比可以作为青贮玉米品质的简捷评价指标。

The yield and quality of silage corn are closely related to the harvest time.The plant,ear and grain related silage quality indexes at the stage of 1/2 kernel milk line were studied to provide instruction for determining suitable harvest time and variety selection in silage corn production.The experiments were conducted in Tongzhou experimental base of Beijing Academy of Agriculture and Forestry Sciences in 2018 and 2019.Totally 40 specific silage corn and dual-purpose corn varieties were selected and sampled at the stage of 1/2 kernel milk line.5 plants for each plot were selected and the fresh weight of stems,leaves,sheaths,ears(without bracts),bracts,rachises and grains of the plant were weighed.The whole plant was baked in 105℃oven for 30 minutes,and then dried at 60℃to constant weight,the dry weight was weighed and then used to test the starch content.The result showed that:There were significant differences in the ratios of ear and kernel fresh weight to plant fresh weight(FWe/FWp,FWk/FWp),and that of kernel dry weight to plant dry weight(DWk/DWp)among different silage corn types and varieties at the stage of 1/2 kernel milk line.The ratios of FWe/FWp,FWk/FWp and DWk/DWp for all the tested varieties averaged 30.2%,20.9%,41.1%and ranged 25.5%-35.7%,16.2%-26.4%,33.6%-48.0%,respectively,with the dual-purpose type were 1.5,3.8 and 5.6 percentage point higher than that of specific silage type.The average plant water content of all the varieties was 68.8%(ranged 63.1%-73.6%),with the specific silage and the dual-purpose type was 70.1%and 67.3%,respectively.The average kernel water content of all the varieties was 39.0%(ranged 35.4%-43.6%),with the specific silage and the dual-purpose type was 39.6%and 38.3%,respectively.The average plant starch content of all the varieties was 30.9%(ranged 25.3%-35.6%).JKQZ368 was the highest(32.9%)and DJJ23 was the lowest(25.3%)among the specific silage varieties;JK968(35.6%)and JNK728(35.6%)were the highest,and MC859 was the lowest(28.3%)among the dual-purpose varieties.The average plant starch content of the specific silage varieties was 29.6%,which 2.9 percentage point lower than that of the dual-purpose varieties(32.5%).At the stage of 1/2 kernel milk line,the average plant and kernel water content of all the varieties was 68.8%,39.0%,and the average starch content was 30.9%;the ratios of FWe/FWp,FWk/FWp and DWk/DWp for all the tested varieties averaged 30.2%,20.9%and 41.1%.During the suitable harvest period,the ratio of FWe/FWp of specific silage/dual-purpose corn varieties was≥30%(the ratio of FWk/FWp was≥20%,and that of DWk/DWp was≥40%),the dry biomass content was≥30%and the starch content was≥30%.So,we suggested that the ratio of FWe/FWp could be used as a simple index for evaluating the quality of silage maize.