| Rice is one of the most important food crops in China and plays a very important role in ensuring food security in China.Heilongjiang Province is a big rice planting province in China,and its rice production plays a very important role in China’s grain production.However,due to the low temperature and other problems,the yield of rice in cold regions of Heilongjiang Province is seriously restricted,and plastic film mulching cultivation can solve the influence of low temperature and chilling injury.Considering that the agricultural production needs to protect the ecological environment and meet the requirements of sustainable development of agriculture,this paper takes rice in the cold region of Heilongjiang Province as the research object.By measuring the soil water and heat,photosynthetic characteristics,dry matter transport and yield of rice under two kinds of biodegradable plastic film mulching and two kinds of water-saving irrigation methods,the temporal and spatial variation characteristics of soil water and heat and the changes of photosynthetic intensity,dry matter transport and yield of rice under different treatments were analyzed,and the response mechanism of soil water and heat,photosynthetic characteristics and yield of rice to different plastic film mulching irrigation methods was revealed.The comprehensive effect of different plastic film mulching irrigation methods was evaluated by comprehensive index method,and the most suitable combination of plastic film mulching and water-saving irrigation methods was screened out.The main conclusions are as follows:(1)When rice is harvested,the degradation rates of the two kinds of biodegradable plastic films are over 80%.The degradation rates of the two kinds of mulch films increased gradually with the change of time,and the maximum rate was above 1.3%/d.Two kinds of biodegradable mulch films enter each degradation period at different times.In the first two degradation periods,white mulch film enters each degradation period about 2 days earlier than black mulch film,and the cracking period begins,and black mulch film enters each degradation period 5-8 days earlier than white mulch film.(2)Under plastic film mulching irrigation,the soil moisture content in different growth stages decreased gradually with the increase of soil depth,and the soil temperature in other growth stages except at the end of tillering showed a downward trend with the deepening of soil layer.Covering with plastic film can improve soil moisture and soil temperature in 0-15 cm soil layer by0.25%-13.98% and 1.07%-9.00%,respectively.The effect of mulching with black plastic film on soil moisture and soil temperature in 0-5cm soil layer is stronger than that with white plastic film.On the whole,different irrigation methods have weak influence on soil temperature,and the influence law on soil moisture content changes with growth period.In the first two growth periods,the soil moisture content under controlled irrigation increased by 0.19%-12.01% compared with ridge irrigation,and decreased by 0.63%-13.51% compared with ridge irrigation in the last two growth periods.The effect of plastic film mulching irrigation on the vertical change of soil temperature was not obvious.The effect of plastic film mulching irrigation on the vertical change of soil moisture content was 1.45% higher in the soil layer above 10 cm,and 0.50%-7.73% lower in the soil layer below 10 cm.(3)The net photosynthetic rate of rice leaves increased by 0.73%-18.33% under plastic film mulching irrigation;Except for jointing and booting stage,the transpiration rate of rice leaves increased by 1.65%-18.16% under plastic film mulching irrigation,and the stomatal conductance of rice leaves increased by 4.55%-75.00% only under ridge irrigation with plastic film mulching;Except for controlling irrigation methods at jointing and booting stage,the chlorophyll content increased by 0.62%-21.38% under plastic film mulching irrigation at other growth stages.Plastic film mulching irrigation increased the dry matter transport rate of rice stem and leaf by4.13%-35.88% and the contribution rate of rice grain by 9.40%-38.85%.Except the combination of controlled irrigation and non-plastic film mulching,other plastic film mulching irrigation treatments can increase the yield by increasing the effective panicle number,grain number per panicle and 1000-grain weight,and the yield increase range is 4.24%-20.81%.(4)There was a positive correlation between soil water and heat and photosynthetic characteristics,yield and its components of rice.With the increase of soil depth,the correlation degree between net photosynthetic rate,grains per panicle and effective panicle and soil temperature decreased first and then increased,while the correlation degree between transpiration rate,stomatal conductance and rice yield and soil temperature decreased gradually,while the correlation degree between 1000-grain weight and soil temperature showed an increasing trend.With the increase of soil depth,the correlation degree between different photosynthetic characteristics and rice yield and soil moisture content decreased first and then increased,while the correlation degree between yield components and soil moisture content showed a downward trend.By comprehensive index method,soil moisture content,soil temperature,chlorophyll content,net photosynthetic rate,transpiration rate,stomatal conductance,stem and leaf dry matter transport rate,grain contribution rate,effective spike number,grain number per spike,1000-grain weight,yield and plastic film residue rate were used as evaluation indexes to comprehensively evaluate plastic film mulching irrigation.The evaluation results showed that the combined treatment of ridge irrigation and black plastic film mulching had the best comprehensive effect on soil hydrothermal environment,crop physiological growth and ecological environment. |
PDF Full Text Request