The normal growth and development of crops and yield formation are the organic processes of photosynthesis in the aboveground and nutrients and water partitioning in the underground root groups. Most of the cultivation measures such as soil improvement, fertilization, irrigation, and cultivator in the production process directly act on the root system, thereby regulating the development of the aboveground and the improvement of the final yield. Therefore, the study of root system becomes more and more important in high yield cultivation.
However, because the root system is deeply buried in the soil, the research is difficult, and it is rare to live in this area to carry out this work. Since 1988, we have conducted a series of studies on the configuration and dynamic construction rules of the root systems of the two major crops of cotton and maize and the impact of production measures on the root system in the area using a root analyzer. The comprehensive report is as follows. The further high yield of corn provides some theoretical basis and technical measures.
1 Materials and methods
The experiment was completed at the Experimental Station of the Faculty of Agronomy from 1988 to 1993. The test site is loam soil, 0-20 cm tillage layer contains 1.50% organic matter. The cotton test variety was Xinluzao 1, and a total of three groups of tests were set up for density, irrigation, and coating. Planting methods are all 60- to 30-cm wide and narrow rows. The conventional planting density in the text is 666.7 m2 (1 mu old, the same below) 1 x 104 plants with a 15 cm spacing. Maize root system research set three varieties of varieties, density and chemical control. 60cm and other row spacing planting, conventional cultivation refers to the species SC704, the density of 666.7m23705 strains, plant spacing of 30cm. The area of ​​all test plots was 29.0 to 82.8 m2, repeated 2 to 5 times. There is no weeds during childbirth, and other management is the same as usual.
The root biomass was excavated using a two-way sectioning method, that is, within the area of ​​land occupied by individual plants in the field, cutting from the ground surface to a layer of every 10 cm downward, and digging until the root segment was not seen; each layer was centered on plants, Between the lines on both sides is cut in units of 10cm. Each excavated soil was collected, rooted, separated, washed, dried and weighed. The root system of the crop was measured and observed using a root analyzer. Each treatment process digs 3 to 5 plants. All the excavated plants were measured for their green leaf area and the weight of various organs in the shoot, and they were measured at maturity. The dried root samples were weighed and measured for root nitrogen (N), phosphorus (P2O5), potassium (K2O), and soluble sugar content.
2 Results and Analysis
2.1 Root Configuration Distribution
1) Longitudinal configuration distribution
Through studies on different varieties, growth stages and treatments of various regulatory measures, it is shown that the distribution of root biomass of cotton and maize in the root volume is a tapered negative exponential decreasing pattern from top to bottom:
y=Ae-Bx, where y is the root weight (mg), x is the soil depth (cm), A is a constant, B is a decreasing rate, the smaller the ?B? value, the y value decreases as the x value increases The smaller the value, the greater the amount of deep soil roots. Under the conventional field cultivation method, the vertical distribution of the root system of cotton in Xinluzao No. 1 was y=3294e-0.0538x, r=0.916**, while that of the largest amount of root was y=2097e-0.0475x,r. = 0.822**; the silking stage SC704 with the largest corn root volume was y=17114e-0.0532x, r=0.958**.
In different growth periods, the distribution of cotton and corn root groups is also different. The root system of cotton seedlings is mainly distributed in the 40cm soil layer on the surface. The root weight in the soil layer below 40cm in the beginning bud stage accounts for only 1.6% of the total root volume. After budding, the root system rapidly expands downwards, and the depth of the soil reaches 120cm in the initial flowering stage. Bell period up to 150cm. After entering the boll opening stage, the root system is almost no longer under the bar. The amount of roots distributed in the 20 and 40 cm soil layers over the entire growth period was 52.4% and 73.3%, respectively.
The distribution of maize roots at the seedling stage was also shallow. The root weight of the soil below 40 cm was only 1.8% of the total root mass measured in the previous week. After the pip, the root system quickly stretched downwards, until the silking stage can be tied down to a depth of about 160 cm in the soil, and although it is almost no longer under the bar, the root volume in the deeper soil still increases. The amount of roots distributed in 20cm and 40cm soil layers near the surface during the whole growth period was 69.2% and 79.5%, respectively.
2) Characteristics of lateral configuration distribution
Root biomass (Y, root dry weight density in mg/cm3) with the lateral distance (x, cm) of the main stem conforms to the sigmoid curve equation model (y=1/A+Be-x), such as silking stage SC704 ( 1.5cm spacing arrangement, simulated no interaction between strains) y=1/(0.1905-28.1071ex), r=0.995**. Under conventional cultivation conditions, more than 78.2% of the root volume of cotton was distributed within 0-15cm on both sides of the plant, and this proportion was continuously reduced along with the delay of the growth period, reaching the lowest level during the flowering period, and the maturity of the boll opening period. This rebound may be related to the large amount of nutrient input into the upper roots of the late cotton plants (Table 1). About 90% of the maize root system was concentrated in the range of 0-20cm from the plant, and the distribution of SC704 and Shidan early root group was more compact than that of Xinyu 4 (Table 2). The pattern was distributed in the middle 10cm interval of the wide row. Less than 10% of the root volume is adjacent to two rows, and less than 15% of the root volume is distributed in the middle 20cm of two rows of corn planted in 60cm and other rows. Therefore, the contraction of the increasing strains may make the roots of the population more evenly distributed. It facilitates the absorption of soil moisture and nutrients. In addition, considering the vertical and lateral distributions, the root systems of cotton and corn are the configuration types of the absolute amount of roots in the upper soil layer, of which more than 57% of cotton roots are distributed within 15cm depth and 40cm depth on both sides of the plant, while maize is 78%. The above root volume was distributed in the soil 40 cm deep from the plant 20 cm deep. Fertilization should fully consider this feature, such as mineral fertilizers such as phosphate fertilizers with poor mobility should be applied in about 10cm from the plant, and the application of caverns is better than the application. In addition, depending on the fattening habit of root growth, deeper fertilization can be used to increase deep root volume, make full use of deep soil nutrients and moisture, and prevent premature aging and increase yield.
2.2 The roots of the crop have not only reached the depth of the root system, but also the root volume, root activity, and root nutrition have changed dynamically with time.
1) Dynamic changes of cotton root biomass
From the emergence to the stalking, the root biomass of cotton was increased along with the upper part of the ground with the sigmoid curve of the growth period, until the final flocculation reached the maximum. The growth of cotton roots can be roughly divided into four stages: slow growth at the seedling stage, rapid growth at the bud stage, steady growth at the flowering and bolling stage, and slower growth at the boll opening stage. The corresponding root growth rates (CGR) were 6.9, 84.6, 37.4, and 4.4 mg/plant d, which accounted for 6.8%, 52.2%, 31.7%, and 7.3% of the total biomass. The amount of roots in Shenglei period has exceeded half of the total root volume; the CGR of the four stages aboveground is corresponding to 208.8, 454.
At 1,662.7 and 202.9 mg/strain, the accumulation accounted for 7.4%, 21.2%, 44.4%, and 26.4% of the total biomass. The growth of the boll period was the fastest, and the peak of growth was later than the root system (Table 3). It can be seen that cotton seedlings should be early soil loosening, early application of Miaofei, and promote the rapid root rooting and lateral roots to achieve strong seedlings early. In the period when the root system grows most vigorously during the budding period, the bud fertilizer should be deepened, and the roots should be prolific and deep. During the flowering and bolling period, sufficient plentiful fertilizer and water supply is ensured in the plough layer, and the physiological function of the cotton root is fully exerted to promote the multi-kidney peach on the ground. During the mature period of boll opening, we must pay attention to the coordination of fertilizer, water and gas, protect the normal physiological functions of the middle and lower leaves, and prevent the root growth from decelerating too early and too fast, so as to improve the quality and yield of cotton.
2) Dynamic changes of maize root biomass
From emergence to maturity, the root weight of maize showed a single-peak curve change and reached the maximum during silking. The growth and decline can be roughly divided into three stages: slow growth at the seedling stage, rapid growth at the mating and booting stage, and decline and decline at the maturing maturity stage. Corresponding stages, the root CGRs were 49.4, 437.6, and -135.8 mg/plant d. After flowering, the growth center was transferred to the grains, the roots began to decline, and some nutrients were transported outwards. The root weight was reduced to 71.4% of the silking stage at maturity.
At the same time, the above-ground biomass of maize showed an S-curve change, reaching 0.1%, 1.0%, and 24.5% of the maximum biomass during the weaning period, the week before the festival, the booting stage, the silking stage, the milk ripening stage and the ripening stage, respectively. %, 50.1%, and 100.0%. Aboveground biomass of about 50% was accumulated after silking, and the crown-root ratio increased with the growth period (Table 4). Accordingly, in production, a strong root system should be established before silking to ensure high yield, and sufficient water and nutrients should be supplied during flowering and grain filling, and the number of roots in the lower layers and the vitality of the root system should be increased to prevent premature aging of leaves. The grain laid the foundation for regaining high yields.
3) Characteristics of nutrient accumulation in cotton roots
The nutrient concentration of nitrogen, phosphorus, and potassium in the cotton root system gradually decreased from the seedling stage to the flowering stage, and the flocculation period rose again. The period of the most uptake of cotton roots is the bud period, which is consistent with the change of the root biomass. According to the determination of the initial flowering period, the accumulation of nitrogen, phosphorus, and potassium in the root system has reached 61.48%, 65.06%, and 68.09%, respectively. From flowering to boll, photosynthetic products and mineral nutrients were more concentrated in the shoots due to the rapid growth in the shoots. Although the root biomass was still increasing, the root nutrient accumulation was significantly slowed (Table 5). Therefore, in production practice, timely application of quick-acting fertilizers at the flower bud stage and promotion of root growth and nutrient accumulation will undoubtedly create a strong root system, ensure the full development of cotton bolls, and prevent late aging from having a good impact.
4) The characteristics of corn root nutrition accumulation
The nutrient concentration contained in the root system of maize has been declining from emergence to maturity. For example, the content of nitrogen in the roots was 2.06%, 1.44%, and 1.32%, respectively, as determined by the week before SC704, booting, silking, milk ripening, and maturing. At 1.16% and 0.88%, the contents of soluble sugars in roots were 5.91%, 2.05%, 4.6%, 3.32%, and 0.99%, respectively, and two peaks were formed before and after silking. The sugar-nitrogen ratio of roots was 2.87, 1.42, 3.60, 2.
At 86 and 1.13, the trend was similar to that of soluble sugar, and the silking period was the highest. The soluble sugar content and the ratio of sugar to nitrogen in the root of booting stage showed a trough, which may be due to the rapid growth and extension of stems and leaves, the strong differentiation of male and female spikes, the fastest growing stage of plant growth, and the consumption of more sugar. In addition, the root nutrient accumulation in maize showed the same unimodal curve as the root weight. The silking period was the largest, and the filling maturity period decreased. It may be related to the decline of root system after rooting and nutrient transport to the shoot and grain. The reduction rate from spinning to ripening nutrients was 29.11% to 44.87%, which was much lower than that of biomass. The decrease in potassium was the highest among the three elements, indicating that potassium was highly recyclable in plants (Table 6). .
5) Root biomass and nutrient accumulation at maturity
The roots of crops are the important sources of soil organic matter, especially in the arid desert ecological conditions in Xinjiang. It has an extremely important role in improving farmland ecology and post-crop growth.
The results of this study indicate that after planting Xinluzao No. 1 cotton, 66.93kg of root dry matter, 0.53kg of pure nitrogen, 0.14kg of phosphorus, and 0.67kg of potassium can be retained in 666.7m2 of soil every year. After planting SC704 corn, residual dry matter of roots can be obtained. Kg, containing pure nitrogen 0.63kg, phosphorus 0.15kg, potassium 0.63kg, while planting stone single early corn residues were only 27.97, 0.33, 0.08 and 0.24kg. The above residue is generally less than the Mainland.
3 Conclusion
In order to tap the yield-increasing potential of cotton and corn, it is necessary to carry out further in-depth research on the root system. Future research on root systems should pay attention not only to the number of root systems but also to comprehensively examine the growth of roots in terms of activity and function, and their relationship with aboveground traits, especially with respect to yield formation. At the same time, we should also strengthen the study of the roots of the genetic laws and environmental factors on the impact of the root; crop resistance and root morphology and physiology; root physiological activity and rhizosphere microbial activity and other issues, the introduction of root system control technology hardware, to improve Root water, fertilizer utilization, increase production and service.
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