Influence mechanism of soil pH fertilization strategy and fungal community on agricultural production

2020-09-26 05:13:46

[ Instrument R & D of Instrument Network ] In recent decades, the application of chemical fertilizers has played a crucial role in increasing crop yields, but it also brings about problems such as soil acidification and changes in microbial communities. Therefore, it is generally considered not to have in agricultural production. Sustainability. The combined application of chemical fertilizers and organic fertilizers can not only bring high crop yields, but also alleviate soil acidification and maintain soil microbial diversity, which is considered to be a strategy for farmland fertilization management. However, in the past, many of the problems of soil acidification caused by fertilization have been studied in large-scale areas, and most of them have occurred in acid soils. There have been few studies on acidification of alkaline soils caused by long-term application of chemical fertilizers. In addition, there are few studies comparing the different responses of fungal communities in acidic and alkaline soils to long-term application of chemical and organic fertilizers. Therefore, it is of great significance to systematically study the relationship between fertilization strategy and soil background pH, fungal community and agricultural production.

The research team of Zhang Jiabao, Nanjing Institute of Soil Science, Chinese Academy of Sciences, used seven field trials with long-term fertilization for more than 25 years as a research platform to analyze the crop yield, soil nutrients and fungal communities of the three treatments without fertilization, chemical fertilizer application and organic fertilizer application The structure reveals the effect mechanism of soil pH-based fertilization strategies and fungal communities on agricultural production. The study found that for acidic soils (pH <5.70) in three locations of Jinxian, Qiyang and Shenyang, the long-term application of chemical fertilizers resulted in a decrease in soil pH of up to 1.20 units, and the combination of chemical fertilizers and organic fertilizers significantly increased the soil pH; chemical fertilizers The increase of crop yield under the application of organic fertilizer was significantly higher than that of chemical fertilizer; in addition, the combined application of chemical fertilizer and organic fertilizer led to a significant increase in the relative abundance of the saprophytic fungi Mortierella and Pseudaleuria. In acid soils, the soil pH is directly related to the abundance of Mortierella, and the enrichment of Mortierella has a direct positive effect on crop yield. For the alkaline soils (pH> 8.11) in Zhengzhou, Yanting, Changwu and Fukang, compared with no fertilization, the continuous application of chemical fertilizers for many years reduced the soil pH by only 0.29 units at the most, while the combined application of chemical fertilizers There was no significant increase in soil pH under the treatment of organic fertilizer; the yield of crops treated with chemical fertilizer and chemical fertilizer combined with organic fertilizer was basically the same, and both significantly increased the relative abundance of Ascomycota. Unlike acid soils, the available phosphorus and C: N ratio in the soil directly or indirectly affect the crop yield of alkaline soils, not the soil pH. These results indicate that farmland fertilization strategies depend on the soil background pH, and acid soils must use chemical fertilizers combined with organic fertilizers to prevent soil acidification, while reasonable application of chemical fertilizers in alkaline soils can still maintain high crop yields and soil sustainability. This study provides a theoretical basis for optimizing fertilization strategies in different regions and improving fungal communities to support sustainable agricultural development.

The research results were published in Agriculture, Ecosystems & Environment. The research was supported by national key research and development plan projects (2016YFD0300802, 2016YFD0200107), the National Natural Science Foundation of China (41807017, 41471182, 41530857, 41671228), and the Chinese Academy of Sciences STS project (KFJSTS-ZDTP-054).

The so-called aligning bearing is that the raceway raceway is spherical, and it can adapt to the angular displacement between the two raceways, which is mainly supported by radial load, and can also bear a small number of two-way axial loads.
Characteristics of core bearing
It is mainly subjected to radial load, and it can also bear a small amount of bidirectional axial load.

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Tune ball bearing editing
The center ball bearing is the inner ring of the two raceways and the outer ring of the raceway for the spherical surface, and the ball bearing is assembled with a ball shaped roller. It can bear a large radial load and also bear a certain axial load, as shown in Figure 1. The outer raceway of this kind of bearing is spherical, so it has the performance of adjusting center.
The main features of the ball bearing are as follows:
(1) the outer race raceway of the ball aligning ball bearing is a part of the sphere. The center of curvature is on the bearing axis. Therefore, the bearing has the function of adjusting the center, and it can be automatically adjusted when the shaft and shell appear flexure, and does not increase the bearing burden.
(2) an appropriate amount of axial load that can bear radial load and two directions. But it can't bear the torque load.
This kind of bearing has smaller contact angle, almost no contact angle under axial load, small axial load capacity, large radial load capacity, and suitable for heavy load and impact load.
(3) the double row center ball bearing with tightened and locking nuts can be installed at any position on the optical axis and does not need to be positioned on the shoulder.
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Spherical Roller Bearings
Spherical Roller Bearing is in the two groove of the inner ring and outer ring raceways between Spherical Bearing assembly, a drum shaped roller, as shown in figure 3. Spherical Roller Bearing with two rollers, mainly bear radial load, also can withstand any direction of the amount of axial load; radial load capacity is very high, especially suitable for radial heavy loads or vibration, but unable to bear pure axial load.
The main characteristics of the spherical roller bearing:
(1) bearing with self-aligning ball like outer ring spherical roller bearing raceway is a part of spherical surface, the curvature center on the bearing axis, the bearing outer ring raceway is spherical shape, so its self-aligning performance is good, can compensate concentricity error, thus can realize the automatic aligning.
(2) in the section perpendicular to the rolling direction, the roller busbar is a curve, which fits well with the inside and outside raceway. The roller and raceway are linear contacts, which can bear radial load and axial load, and has good impact resistance.
(3) roller and roller bearing raceway match well, and are therefore relatively serious curve generatrix, sliding, friction than cylindrical roller bearings, spherical roller bearings are allowed so low working speed.
(4) the heart fades with a normal roller bearing non symmetrical roller, it will generate an axial force, roller by the force and the center fixed flange contact, spherical roller bearing symmetrical roller, it can move along the axial direction using the middle movable baffle ring, so no longer block roller center the edge of the constraints, and saves the recess of the inner raceway, the roller can be used longer, so as to improve the bearing capacity.
(5) single row self-aligning roller bearing contact angle is 0. Under axial load, the contact angle did not change significantly, the axial load will be very small contact forces generated great between roller and raceway, so when the axial load is greater than the radial load, the loads of single row spherical roller bearing can bear radial and axial.
(6) bearing with self-aligning ball like set with tight double row spherical roller bearing can be installed in any position on the optical axis, do not need to process the positioning shaft shoulder.
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Spherical Plain Bearing

Spherical Plain Bearing,Cheap Spherical Plain Bearing,High Precision Spherical Plain Bearing,Radial Spherical Plain Bearings

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