Field estimation of maize plant height at jointing stage using an RGB-D camera

Plant height can be used for assessing plant vigor and predicting biomass and yield. Manual measurement of plant height is time-consuming and labor-intensive. We describe a method for measuring maize plant height using an RGB-D camera that captures a color image and depth information of plants under field conditions. The color image was first processed to locate its central area using the S component in HSV color space and the Density-Based Spatial Clustering of Applications with Noise algorithm. Testing showed that the central areas of plants could be accurately located. The point cloud data were then clustered and the plant was extracted based on the located central area. The point cloud data were further processed to generate skeletons, whose end points were detected and used to extract the highest points of the central leaves. Finally, the height differences between the ground and the highest points of the central leaves were calculated to determine plant heights. The coefficients of determination for plant heights manually measured and estimated by the proposed approach were all greater than 0.95. The method can effectively extract the plant from overlapping leaves and estimate its plant height. The proposed method may facilitate maize height measurement and monitoring under field conditions.

Optimized design and experiment of spiral-type intra-row weeding actuator for maize(Zea mays L.)planting

Mechanical weeding not only avoids crop herbicide residue but also protects the ecological environment.Compared with mechanical inter-row weeding,mechanical intra-row weeding needs to avoid crop plants,which is conducive to causing a higher rate of seedling damage.In order to realize maize(Zea mays L.)intra-row weeding,a maize intra-row weeding mechanism was designed in this study.The mechanism can detect maize seedlings by infrared beam tube,then a sliding-cutting bevel tool moves spirally amid maize seedlings,so as to eradicate intra-row weeds.A field experiment was conducted under the following experimental conditions:the bevel tool rotation speed was 800-1400 r/min,the mechanism forward speed was 4-7 km/h,and the bevel tool depth was 2-14 cm,the experimental results illustrated that the mechanism’s average weeding rate and seedling damage rate were 95.8%and 0.6%,respectively.The variance analysis showed that the primary and secondary factors that affecting the weeding rate and seedling damage rate were the same,which were bevel tool rotation speed,mechanism forward speed,bevel tool depth in soil in a descending order according to the significances.The result of the field experiment may provide a reference for intra-row weeding device design.

Planting uniformity performance of motor-driven maize precision seeding systems

Low accuracy planting uniformity affects yield.Seed meter type and forward speed typically interfere with the planting uniformity accuracy of motor-driven seeding systems.Two types of maize precision planters equipped with motor-driven planting systems are investigated in this study to ascertain the rule of planting uniformity in both simulated and field speeds.The simulated speed increases from 5 to 12 km/h at a 1 km/h interval in a laboratory environment.The test results show that the quality of feed index(QTFI)of the two planters decreased by 16.79%and 9.88%.This is primarily attributed to the increase in the miss index(MISS)by 11.62%and 9.70%,respectively.The field speed was set to four levels from 5 to 12 km/h in a field environment.The plant spacing scatter distribution results were analyzed,and the results of the two planters indicated that the average positive difference of the two planters linearly increased with the forward speed,and the negative difference of the two planters did not exhibit a linear correlation.The number of positive moving average points was 2.49 times greater than that of the negative moving average points of the finger pick-up maize precision planter,and 4.49 times in the air-suction maize precision planter.The results indicated that the increase of the positive difference of plant spacing is the major effect factor in the field planting uniformity of the two motor-driven maize precision planters.In addition,the plant spacing corresponded to the distribution frequency of the two planters in field was close to the target seed spacing of 25 cm with a max coefficient of variation(CV)of 21.55%and 20.66%,respectively,and those plant spacing values corresponded to max distribution frequency of the two planters at the four level field speeds were(24.69±0.63)cm and(25.63±0.32)cm,respectively.However,the multiples index(MUL)changed randomly affected by the increasing speed.The research results provide a direction for the optimization design of motor-driven maize precision planters.