Impact of soil conditions on the physiological characteristics of maize plants in an arid region, Northwest China

Overuse of irrigation water to ensure the crop yield of maize plants has caused serious water shortage problems in the middle reach of Heihe River, China. Thus, further research on the physiological characteristics, i.e., photosynthetic rate and leaf transpiration rate, are urgently needed to develop an efficient irrigation management system. In this paper, we selected two common soil textures （sandy loam, sand） and three one-time irrigation volumes （60 mm, 20 mm, 0 mm） in order to analyze the impact of soil conditions on the physiological characteristics of maize plants. Physiological and meteorological factors, soil water content and plant growing parameters were synchronously monitored on Jun. 30, Jul. 25 and Aug. 27 of 2012. The results indicate that sandy loam is better than sand for the growth of maize plants and single irrigation may provide limited influence on the physiological characteristics. Thus, increasing irrigation times and decreasing one-time volume is suggested for an efficient irrigation system.

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.

The Temporal-Spatial Distribution of Light Intensity in Maize and Soybean Intercropping Systems

Intercropping can improve field microclimates, decrease the incidence of crop diseases, and increase crop yields, but the reasons for this remain unknown. Solar radiation is the most important environmental influence. To understand the mechanisms of intercropping we established an experiment consisting of three cropping patterns： a monocropping control {treatment A） and two intercropping treatments （B： two rows of maize and two rows of soybean intercropping; C： two rows of maize and four rows of soybean intercropping）. Results show that compared to monocropping, intercropping increased the amount of light penetrating to inferior leaves in maize plants. Light intensity reaching maize plants at the heading stage in intercropping increased over two-fold at 30 cm above ground and 10-fold at 70 cm above ground, compared with monocropping. At the flowering to maturity stage, light intensity at 110, 160 and 210 cm above ground among maize plants was greatly increased in intercropping compared with monocropping, by some five-fold, two-fold and 12%, respectively. Moreover, light intensity declined more slowly at the measured heights in the intercropping system compared with monocropping. From the 7-18th leaf, light intensity per leaf increased two-fold in intercropping compared with monocropping. Daily light duration increased more than a mean of 5 h per day per leaf in intercropping compared with monocropping. The biological characters of maize including thousand kernel weight, yield per plant and area of ear leaves were all greater in intercropping than monocropping. These results suggest that, for maize, intercropping improves light density and duration significantly and this may contribute to biomass and yield increases.

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.