Effects Of Density And Plant Height On Reproductive Allocation Of Rice And Paddy Soil Nutrient Change Research

The wetland is a unique habitat and important land resources.Wetlands have many functions.In recent years,American scholar Professor Mitsch Willian has actively promoted the new concept of wetland agriculture(Wetlaculture),that is,the nutrients accumulated in the wetland are used as fertilizers for the growth of crops,and the wetland-agriculture-wetland rotation system.The growth of crops and the number of years of crop rotation are studied without the addition of fertilization.This study was guided by this concept.After the wetland was reclaimed as a paddy field,the effects of different interpolation densities on rice growth,reproductive allocation,and changes in nutrients in the paddy soil were studied.The rice variety was"Yan jing-30",the study used normal irrigation and has set up no-fertilization test series.The density was:13 holes/m~2(6 holes per test box,referred to as density 6),18 holes/m~2(8holes per test box,referred to as density 8),27 holes/m~2(12 holes per test box,referred to as density 12),34 holes/m~2(15 holes per test box,referred to as density 15)and 45holes/m~2(20 holes per test box,referred to as density 20).Observed its growth,development and yield,and at the same time,explored its resource allocation strategy and the restriction of density on plant height;combined with the physical and chemical properties of the test field,the nutrient consumption status of rice planting and background soil was analyzed.The main results showed that:(1)Analysis of the soil pH,organic matter,total nitrogen,ammonium nitrogen,total phosphorus and available phosphorus were used to explore the consumption of various nutrients in the soil by rice cultivation without fertilization.At each planting density,soil pH increased significantly at the jointing booting stage of rice.At each planting density,the organic matter content decreased significantly at the jointing booting stage.At the density of 6,8 and 12,the total nitrogen content of the soil declined at the jointing booting stage,then it rebounded,but it did not reach the pre-transplant content.At the blank test and density 15 and density 20,the total nitrogen content of the soil has been reduced.At each planting density,the soil ammonium nitrogen content decreased at the jointing booting stage,increased after harvest but decreased compared to before transplant.At all planting densities,the soil total phosphorus content showed a downward trend with time,especially the consumption was most obvious at transplanting to the jointing booting period;on the contrary,the soil of the blank test(without rice cultivation)had a rise in total phosphorus content during the rice growth period,which may be related to the plant debris in the biodegradable soil.At each planting density,the available phosphorus content in the soil decreased.This result revealed the consumption of various nutrients in the soil by rice cultivation.(2)In the absence of fertilization,the spatial and temporal distribution patterns and quantitative dynamics of rice growth,rice propagation organs,plant height were analyzed at different density gradients.Low density group had more total heading of rice per hole than high density group and concentrated heading time were later.Rice yield changed with density,density 12,15,and 20 yields are similar,and the test group with density 12 had the highest yield,the test group with the density of 12 also had the highest seed setting rate.As the density increased,the plant height decreased,the relationship between plant height and planting density was:density 6 group>density 8 group>density 12 group>density 15 group>density 20 group.The rice in the test group with density 6,8 and 12 has more biomass allocation for seed propagation than other tissues and organs.(3)The harvested rice was grouped by plant height,and the reproduction and distribution strategies of different plant height groups were analyzed.There is a significant dependence relationship between rice resource allocation strategy and plant height.The proportion of rice biomass allocated to seeds increased first and then decreased with the plant height,and reached a peak when the plant height was 97.8±5cm.The results of single factor analysis of variance showed that when the rice is82.9cm?plant height?112.8cm,the biomass allocation for reproductive growth was significantly larger than the test group with plant height?82.9cm.(4)According to"Quality Rice"(GB/T 17891-2017),brown rice rate(BR),imperfect grain content(UGR),polished rice rate(MR),polished rice rate(HR),moisture content(MC),appearance quality and other indicators were comprehensive evaluated?When the plant height is 82.9cm?plant height?112.8cm,the rice quality was significantly higher than that of other plants.With the increase of plant height,rice quality showed a change that increased first and then decreased.Through the above conclusions,it can be considered that 27 holes/m~2 can be used as the recommended planting density for wetland agriculture,because at this density,the yield and seed setting rate were the highest,and the ratio of rice used for reproduction and distribution was high;corresponding to the ideal rice plant height of good rice quality,the distribution frequency was also larger at this density.