Effect Of Mechanical Harvesting Of Main Crop On The Grain Yield And Quality Of Ratoon Crop In Ratooned Rice

Ratoon rice is the production of a second rice crop from the stubble left behind after the main crop has been harvested,which is an important innovation during the period of agricultural transformation in China.When mechanized production is being adopted widely in agriculture,the agronomic management practice suitable for it is lacking.In practice,it was found that plants rolled by chassis of the harvester was slow to recover and the growth of nodal bud was delayed.This led to yield penalty in the ratoon season.Meanwhile,the ventilation and light conditions in the field was changed,and border effect occurred in the non-rolled area,which may compensate the yield loss in the rolled area.For this hypothesis,field experiments were conducted in 2016-2017 of Jiupu country,Chidong town,Qichun County,Hubei Province,China.There were four different harvesting treatments: mechanical harvesting of main crop,mechanical harvesting of main crop and removing the stubble rolled by chassis of the harvester;manual harvesting of main crop and removing the 25.0% or 33.3% stubble;manual harvesting of main crop,and aimed to(1)explore the difference in grain yield of the ratoon season between mechanical harvesting and manual harvesting of the main crop,(2)quantify the yield penalty caused by the reduction of grain yield in the rolled area,(3)quantify the yield benefit caused by the increase of grain yield in the non-rolled area due to the border effect,(4)determine the difference in rice quality of ratoon crop between mechanical harvesting and manual harvesting of main crop.The results showed as follows:1.The grain yield of ratoon rice for Huanghuazhan(HHZ)and Liangyou 6326(LY6326)were 4.93-5.61 t ha-1 and 5.87-6.60 t ha-1,respectively,when the main crop was manually harvested.The grain yield in the ratoon season at mechanical harvesting of the main crop for HHZ and LY6326 were 3.94-5.30 t ha-1 and 4.77-6.85 t ha-1,respectively.There was no difference in grain yield of ratoon season between mechanical harvesting and manual harvesting of the main crop in 2016,while the grain yield of ratoon crop of mechanical harvesting of mian crop was reduced by 18.7%-20.1% compared with that of manual harvesting in 2017.The reason for differences between years was that the rolling rate in 2016 was lower than that of 2017.What'smore,the yield of rolled area in 2016 was higher than that of 2017.2.After mechanical harvesting of the main crop,grain yield of the rolled area in the ratoon season was reduced compared with that of manual harvesting.The yield penalty in the ratoon season caused by the reduction of grain yield in the rolled area was 14.12%-26.50% for HHZ,and 7.2%-27.1% for LY6326.The yield loss in rolled area was mainly due to less spikelets and above the ground total dry weight in plants of the rolled area compared with that of manual harvesting of the main crop.3.In present study,border effect of the non-rolled area was 5.9%-54.2% due to more spikelets and above the ground total dry weight in plants of the border rows.After mechanical harvesting of the main crop,grain yield of the non-rolled area in the ratoon season was increased compared with that of manual harvesting.The yield advantage of non-rolled area resulted from the border effect.The yield benefits due to the increase of grain yield in the non-rolled area of HHZ and LY6326 were 6.8%-8.9% and 8.3%-11.0%,respectively.4.The harvesting method had little effect on milling quality and appearance quality of ratoon rice.There were no significant difference in brown rice rate,milled rice rate,head rice rate,chalky rice rate and chalkiness rate between plants in non-rolled area at mechanical harvesting and plants in manual harvesting.Nevertheless,the brown rice rate,the milled rice rate and head rice rate in the rolled area decreased significantly,and the chalky rice rate and chalkiness significant increased.In summary,the study indicated that the yield benefit of non-rolled area due to border effect can compensate the yield loss in the rolled area but not completely.To lower the yield penalty in the rolled area was the key to eliminate the reduction in grain yield of ratoon season due to the mechanical harvesting of the main crop.And mechanical harvesting of main crop had little effect on milling quality and appearance quality of ratoon rice.