| There are two ways of rice planting:transplanting and direct sowing in Ningxia.Compared with transplanting rice,direct sowing rice has some disadvantages,such as low seeding emergence rate,difficulty in obtaining whole seedlings and uniform seedlings,serious harm of weedy rice,shallow root distribution,and poor resistance of the population.At the same time,it is affected by low-temperature chilling injury and soil salinization,resulting in delayed sowing date and shortened growth period,which seriously affects the yield.Soil-covered direct seeding is a kind of dry direct seeding method.Preliminary research shows that it has the advantages of saving water,improving seedling emergence rate,increasing yield and so on,showing a good application prospect.In order to find out the effects of sowing depth and sowing amount on rice growth and yield under direct seeding with soil cover,this study took Fuyuan No.4,the main rice variety in Ningxia,as experimental material,and carried out research on the emergence rate,seedling quality,population growth and development characteristics and yield of direct seeding with soil cover,the aim was to provide theoretical basis for direct seeding rice cultivation technology.The main results of this study are as following:1.Among the combinations of different sowing depths and sowing amount,the combination of A2B1(sowing depth of 2cm and sowing amount of 112.5kg·hm-2)and A2B2(sowing depth of 2cm and sowing amount of 187.5 kg·hm-2)has the highest emergence rate,and A4B4(sowing depth of 4cm and sowing amount of 337.5 kg·hm-2).2.Different sowing depth and sowing amount significantly affect the seedling quality of rice.Through comprehensive evaluation of the related indexes of seedling quality,A2B2,A2B3(sowing depth of 2cm,sowing amount of 262.5 kg·hm-2),A3B2(sowing depth of 3cm,sowing amount of 187.5 kg·hm-2)and A3B3(sowing depth of 3cm,sowing amount of 262.5 kg·hm-2)3.Among the combinations of different sowing depths and sowing amount,A4B1(sowing depth of 4cm and sowing amount of 112.5 kg·hm-2)has the strongest tillering ability.The earing rate of rice in the combination of 3B1(sowing depth 3cm,sowing amount 112.5 kg·hm-2)was significantly higher than that in other combinations,and the earing rate in the combination of A4B4 was the lowest,which was 40.74%lower than that in A3B1.4.From jointing stage to maturity stage,the dry matter accumulation of A2B4(sowing depth 2cm,sowing amount 337.5 kg·hm-2)and A4B4 combination treatments accounted for the largest proportion of the total biomass,reaching 55.71%and 54.34%respectively,which was significantly higher than other sowing depth and sowing amount combinations.In all combinations,the dry matter accumulation at jointing-heading stage was higher than that at heading-maturity stage.5.Among the treatments with different sowing depths and sowing amount,the SPAD value and photosynthetic characteristics of flag leaves of rice treated with A2B2,A2B3,A3B2 and A3B3 combinations are better than those treated with other sowing depths and sowing rates.At heading stage,the stem injury flow of combination A1B2 and A2B2 was higher than that of other combinations,but from heading stage to grain filling stage,the stem injury flow of all combinations gradually decreased with the growtth process.6.The effects of diferent sowing depths and sowing rates on plant height,seed setting rate and 1000-grain weight are not obvious.The ear length and grain number per ear of combination treatments A1B1(sowing depth 1cm,sowing amount 112.5 kg·hm-2)and A2B1 are higher than those of other treatments,and the yield of combination treatments A3B2 and A3B3 is the highest.7.Through comprehensive evaluation of seedling quality,population growth and development characteristics and yield of direct seeding rice in different combinations,two optimal combinations A3B2 and A3B3 were selected in this study,and the suitable sowing depth of soil-covered direct-seeding mode was 3cm,and the sowing amount was 187.5～262.5 kg·hm-2. |
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