Evaluation Of Single Seeding Method Based On Phenotypes Of Winter Wheat Under No-till System

Wheat is one of major food crops in China.China’s wheat acreage was 24 million hectares in2013.Increase of wheat production was of great significance for China’s food security.Farmers have adopted different wheat planting techniques over the years,for example,conventional drilling,zero tillage drilling,precision drilling,and broadcasting in winter wheat.Many farmers,researchers,and officials in China have been paying close attention to the no-tillage planting approach in recent years.Over the last 20 years,much emphasis has been placed on the precise seeding of wheat,and researchers have established that the yield of precision sowing techniques can be 7.5%to 22.3%higher than traditional sowing.The development of precision single seeding tools could tremendously help in mechanizing direct seeding operations in the field.Academician Yu Songlie of China’s Shandong Agricultural University proposed the precision seeding method.This approach improved most regions of wheat fields in the North China Plain from medium yield levels(5250–7500 kg ha^–1)to high yield levels(more than 7500 kg ha^–1),breaking through long-term stagnating winter wheat yields by lowering seeding amount and enhancing sowing quality.The precision seeding pattern’s cultivation practices focused on improving soil fertility,selecting varieties,cultivating robust seedlings,and maintaining an acceptable population structure.In 1992,this technology was awarded the second place in China’s National Technology Invention Award.Agricultural robot had become an important target in research and development of agricultural machinery engineering.Especially in the recent 20 years,with the development of computer and sensor technologies,numerous researches on this subject,particularly agricultural robots,had been reported.Due to the particular wheat grain geometry,the mechanization of precision seeding technique is still in the research stage and there is inadequate data on the quality of wheat at each growing stage.And also,the effects of the different precise single seeding method and different seeding rate on wheat population development and yield formation under field conditions have not been studied.Keeping all these facts in view,this research was carried out to develop a tool for wheat single seed seeding in field condition,and to assess the influence of different seeding doses on the phenotypes of the aboveground biomass and the root system.Additionally,yield components and grain yield were also analyzed.The results are generalized as follow:1.Effect of no-till precision seeding on wheat（Triticum aestivum l.）population quality at the emergence stageA field experiment was carried out during two consecutive years at Nanjing Agricultural University,Jiangsu Experimental Farm.The objective of the study was to compare the effect of the drill seeding and punch seeding of wheat at the emergence stage.The experiment comprised of three（1.5,3,and 4.5 cm distances between seed）treatments arranged in randomized complete block design with three replications in a plot size of 4 by 5 m.Three densities and two types of sowing subject to the treatment of this studies were recorded as:T1.5,T3,and T4.5 for drill seeding and C1.5,C3,and C4.5 for punch seeding.The emergence time follows a classic S function.Increasing the distance between seeds during seeding,reduces the density of plants and increases the emergence time.The emergence rate for the spacing of 4.5cm between the seeds was high under the no-till drill seeding compared to the no-till punch seeding method.The seeds started growing on the 9^th day.On the 12^th day,the highest germination rate of all the treatments was recorded.The dynamics of the seedling emergence can indicate that the seedlings of different treatments of wheat are showing all one（1）leaf 12 days after seeding.Fifteen（15）days after seeding,one leaf and one heart seedlings appeared under T3 and T4.5,accounting for 17.34%and27%,respectively.With the increase in the distance between seeds,the planting density decreases.The emergence time for the two seasons was relatively high for the seedlings under C1.5 and C3（12,11.7 and 12,12.6 days）and C4.5（11.4 and 11.6）.However,the time taken to reach full emergence varied between 24 and 31 days.During the two seasons of the experiment,a general tendency was observed for the two seeding methods;the reduction of the growth parameters（the dry weight of the roots,the aerial biomass,and the number of roots）seedlings as the planting density increased.However,several parameters showed significant statistical variations,such as the emergence rate by age ratio of the seedlings,the dry weight of the biomass,the leaf area,the dry weight of the roots,the root volume,the length,the root depth,and root/soil ratio.The results showed that competition between plants began to appear at the stage of sowing,and the higher the planting density,the more the growth of the wheat population of individuals is hampered.Beyond the results,we have demonstrated the interest in characterizing the phenotypes of wheat through multiple criteria,also considering the whole plant at the emergence stage.2.Evaluation of single seeding method on aboveground and root system of wheat plant under the no-till systemWe present an evaluation of the single grain seeding method based on the aboveground biomass and root system phenotypes under two seeding methods.The quantitative indicators of aerial biomass and those of the roots were obtained mainly from measurements made on high-resolution images of different parts of the plant on the one hand and direct measurements carried out in the field on the other hand.Several traits show statistically significant variations.Based on the three-view projection area of the wheat plant,the leaf area and aboveground dry weight of wheat under two sowing methods and at three growth periods were predicted using models.Besides,the correlation between the aboveground indicators of the two sowing methods was extremely significant and positive.And also,there was a significant correlation between most of the root system indexes,and between the aboveground and root system indexes.Overall,the results showed that the seeding method and seeding density have an impact on the aboveground and root system indicators of individual plants in the population.At the seedling stage,under the no-till drill seeding method,the linear model outperforms the quadratic model and the exponential model in predicting wheat leaf area.At the tillering,the linear model had a prediction value of 0.938 and0.781under the drill seeding and punch seeding,respectively.At the jointing stage,the linear model gave the best fit between the predicted value of leaf area and the actual measured value under the no till-punch seeding method,with an R² of 0.917.For both seeding methods,the quadratic model is the most accurate in prediction of the aboveground dry weight at the seedling stage of wheat,with the coefficient of determination between the predicted value and the measured value reaching 0.536,while the lowest was 0.504 under the no-till drill seeding.At the tillering stage,the quadratic model is the most well-fitting of the group,with an R² of 0.959.The quadratic and exponential models are the best prediction models for the aboveground dry weight at the jointing stage under no-tillage drill seeding,with an R² of 0.882.At the seedling stage,with the decrease of seeding density,the Gini index of the front view projected area,the extended width between the row,the side view convex area,the top view projected area,and the root dry weight gradually decrease.And also,the Gini index of the leaf area,the front view projected area,the extended width between the rows,the root dry weight,and the total root length all decreased with the decrease in seeding density while the wheat plant was at the tillering stage.However,as the seeding density decreases during the jointing stage,the Gini index of the aboveground and the root system indices rises first,then decreases.Beyond the results,we have demonstrated the interest in characterizing the root phenotypes through multiple criteria,also considering the whole plant and integrating advanced stages.3.Effects of uniform seed-to-seed distance precision seeding on winter wheat（Triticum aestivum l.）population quality at the maturity stagePrevious research has shown that drill seeding produces the best winter wheat grain yields;however,the causes for these high yields and their influence under varied seed-to-seed distances have not been fully investigated.As a result of this,a two-year field experiment was conducted to assess the influence of three different seed distances 1.5cm（T1.5）,3cm（T3）,and 4.5cm（T4.5）on winter wheat to estimate yield and yield components.The three treatments produced statistically（p≤0.05）distinct outcomes in terms of the total number of ears,the total number of grains per ear,the total stem weight,the total weight of the ears,and the total aboveground biomass weight.During the two cropping seasons,there was no difference between the T1.5 and T3 treatments,however,there was a difference when compared to T4.5.As the seed-to-seed distance reduces,intra-plant competition intensifies,reducing the yield per plant,but the final yield per unit area remains the same.The"self-thinning rule"states that when planting density increases,intraspecific competition affects not just individual growth and development,but also plant survival rates.The survival rate of individuals directly shows the phenomena of self-thinning.T4.5 resulted in higher leaf weight,stem weight,ear weight,and aboveground biomass,whereas T1.5 resulted in lower.The grain yield increased considerably when the seed-to-seed distance was reduced,the highest being 6137.8 kg hm^-2 at a seed-to-seed distance of 1.5cm.The results indicated that T1.5 is the best seed-to-seed distance for winter wheat yield and yield components under a no-till system,out of the three seed distances tested.4.Uniform seed-to-seed distance precision seeding:wheat grain yield estimation based on image morphological properties and wheatThe estimation of wheat grain yield based on a composite of morphological features and mass of wheat organs was introduced in this study.The morphological features（length,width,and the perimeter for wheat stem and ear）were extracted by a computer vision system.In order to evaluate the performance of the image processing algorithm,the relationship between the perimeter and the length of the stem for manually measured and estimated values（by image processing）on a selected set of 50 stems for the selected variety"Luyuan 502"was explored in terms of accuracy.The performance was evaluated by correlating the measured and estimated perimeter and length of the wheat stem at an R² of 0.9609 and 0.9779,respectively.The statistical analysis of the 50 single wheat stem and their ear data of both varieties shows the mean values of1.019 g and 1.060 g and a median of 0.949 g and 1.113 g and also a positive skew of 1.225 and0.729 for the varieties"Luyuan 502"and"Zhengmai 9023",respectively.The positive skew of both varieties is indicating an axys-symmetrical distribution.The average and median of the measured parameter are higher than the mode according to the positive values of the skew.Six regression models were developed based on the extracted features.The linear regression based on the wet weight of the stem,the ear,and the leaves outperformed all the other statistical models explored with an R² of 0.9893 and an RMSE of 0.0684 mm in estimating dry grain yield with wet wheat organs mass as the predictors.This proposed system can be applied as a non-destructive in field technique for wheat phenotyping.Additionally,it can be applied to other similar crops.