Effects of Machine-cut Stubble Height on Morphological Development and Grain Yield of Subsequent Ratoon Rice Crop
- 生命科学－已发表论文 
为探索再生稻机械化生产中头季机割高度对再生分蘗生育的影响,设置头季机割高度试验,结果表明:(1)再生分蘗由头季稻桩上的茎生腋芽萌发而来。头季采用低桩机割(割桩高度12cm),割去倒2、3节腋芽,再生季成穗分蘗为倒4、5节腋芽萌发的分蘗及其子蘗,成穗数较多,穗子较大,晚育晚熟;(2)头季采用高桩机割(割桩高度35cm),出现2类株行,其中一类有70%株行,稻桩保留全部茎生腋芽,但以倒2、3节腋芽萌发的分蘗为主,子蘗少,成穗数较少,穗子较小,早育早熟;另一类有30%株行,稻桩遭收割机链轨碾轧,于距地表高15cm左右较细弱的部位折损,倒2、3节腋芽失活,再生季成穗分蘗为倒4、5节腋芽萌发的分蘗及其子蘗,与低桩机割株行类似,穗子较大,晚育晚熟,但两类株行成熟期相距15d,收获顾此失彼;(3)再生稻头季地上部有6个节间,其中着生倒4、5节腋芽所属的2个基部节间粗短坚硬,距地表高(5±2)cm;着生倒2、3节腋芽所属的中部节间细长脆弱,弯曲力矩大,遭收割机链轨碾轧或大风雨袭击时最易折损。头季低桩机割的适宜割桩高度是基部2个节间高度加5~8cm保护段,即距地表高12~15cm,过低将伤及倒4、5节腋芽,过高则出现两类株行,熟期参差。In a mechanized farming experimentation,effects of stubble height of ratoon rice on the tiller growth and development of the subsequent generation of the crop were investigated.The following results were observed.(1)The ratoon tillers grew from germinated cauline axillary buds on the stubbles of the original rice plants.Therefore,the machine-cut,12cm-high stubbles lost the axillary buds in the 2~(nd)and 3~(rd)nodes from top.The effective ratooning tiller panicles in the new crop had to derive from the tillers of germinated axillary buds in the 4~(th)and 5~(th)nodes from top and their filial tillers.This resulted in a more effective formation of panicles and larger spikelet with late development and delayed maturity.(2)The machine-cutting that produced tall stubbles with a height of 35 cm caused the rice to grow into two distinctively different types.One of them had 70% of plant-to-row,whose stubbles retained the entire cauline axillary buds while the ratooning tillers had to depend mostly on the germinated axillary buds in the 2~(nd)and 3~(rd)nodes from top with few filial tillers.Thus,the new plants had less effective panicles,smaller spikelet,as well as earlier development and maturity than control.The other type had 30% of plant-to-row,whose stubbles suffered from mechanical damages in harvesting showing fractures on the slender parts about 15 cm above the ground.The devitalization of axillary buds in the 2~(nd)and 3~(rd)nodes from top appeared to drive the ratooning tiller panicles from tillers of the germinated axillary buds in the 4~(th)and 5~(th)nodes from top and their filial tillers.As a result,the new plants grew similarly to those of low stubbles with large spikelets,late development,and delayed maturity.The ripening of these two types of rice differed in 15 days that hindered synchronized harvesting.And,(3)the new ratoon rice shoots had 6internodes each.Two basal internodes developed from axillary buds in the 4~(th) and 5~(th)nodes from top exhibiting the characteristics of being short,thick,sturdy,and(5±2)cm from ground up in height.On the other hand,the middle internodes from the axillary buds in the 2~(nd)and 3~(rd)nodes from top were slender and fragile with large bending moments,which made the plant susceptible to damages in harvest or by storm.It appeared that too shorta stubble would impair the axillary buds in the 4~(th)and 5~(th)nodes from top,while too tall would end up with plants with separate ripening stages.The optimal height of stubbles for mechanized farming was,consequently,determined to be 12-15 cm that allowed the retention of two basal internodes with a 5-8cm protection section on each stubble.