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Copyright of Journal of Nanjing Agricultural University / Nanjuing Nongye Daxue Xuebao is the property of Journal of Nanjing Agricultural University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Soil compaction risk can be normally assessed, in terms of the relationship between the wheel contacting pressure and the soil pre-consolidation stress. It is still lacking in the evaluation of the damage degree of soil structure that is caused by quantitative mechanical compaction in production scenarios, such as wet tillage and rot under intensive rice farming. In this study, a prediction model of soil compacted bulk density was derived using soil rebound and compression index in paddy fields under intensive production conditions. The improved model was verified by the laboratory uniaxial compression test and in situ flat subsidence test of undamaged soil in paddy fields. An indoor uniaxial compression test was also carried out under the undisturbed soil with different moisture content (15%, 20%, 25%, 30%, and 35%). Among them, there was no change in the bulk density of the undisturbed soil. The transfer functions were constructed for the soil initial bulk density (ρ), initial moisture content (w), elastic compression modulus (Es), plastic compression modulus (Ec), and soil pre-consolidation stress (σpc) after the uniaxial compression test. The coefficient of determination was greater than 0.95 after fitting the test data with each transfer function. The results show that the improved model was operable and accurate using the transfer function. At the same time, the Es presented a significant negative correlation with the ρ, whereas, there was a significant positive correlation with the w. The Es reached the maximum when ρ=1.1 g/cm3 and w=35%. The minimum was obtained, when ρ=1.8 g/cm3 and w=15%. The Es value ranged from 0-0.25 cm/kPa. The Ec presented a significant negative correlation with the ρ, and there was a quadratic polynomial relationship with the w. The Ec reached the maximum when ρ=1.1 g/cm3 and w=25%. The minimum Ec was obtained, when ρ=1.8 g/cm3 and w=15%, where the value ranged from 0-0.8 cm/kPa. There was a significant positive correlation between the σpc and ρ, whereas, a significant negative correlation was found between the σpc and w. The σpc reached the maximum when ρ=1.8 g/cm3 and w=15%. The minimum was obtained, when ρ=1.1 g/cm3 and w=35%. The value ranged from 20-160 kPa. The earth pressure was determined as 30, 60, 90, and 120 kPa in the in-situ flat subsidence test, according to the several types of harvesters. The soil bulk density in the uncompacted area was taken as the initial bulk density, while, the measured bulk density of the soil in the compacted area was as the measured bulk density. The ρ, w, elastic compression modulus, plastic compression modulus, and pre-consolidation pressure from the uncompacted region were then input into the prediction model of soil compacted bulk density to obtain the predicted bulk density. Finally, the measured bulk density was compared with the predicted. In-situ plate sinkage test showed that there was less than 5% error between the measured and the predicted using the transfer function-derived soil elastic compression and plastic compression modulus. At the same time, it was found that the wheel contacting pressure was greater than the soil pre-consolidation stress under the large w and the small ρ. There was a risk of soil compaction, even with the small contacting pressure of the wheel in the harvester. Therefore, a reasonable time and machine type can greatly contribute to the implementation of field tillage. Consequently, the prediction model of soil compaction can be expected to accurately quantify the soil bulk density under mechanical compaction. The finding can provide a strong reference for a better prediction model in regional agricultural usage. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of South China Agricultural University is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nanjing Agricultural University / Nanjuing Nongye Daxue Xuebao is the property of Journal of Nanjing Agricultural University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nanjing Agricultural University / Nanjuing Nongye Daxue Xuebao is the property of Journal of Nanjing Agricultural University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Objectives] Surf act seeding is an important agronomic technology for no-till seeding and inter-cropping systems. Seed germination ami seedling establishment is closely related to the seed-zone micro-climate which affects seed germination and seedling establishment. [Methods] Seed-zone heat and humid status was defined as seed-zone microclimate'. A micro-chip measurement system for seed-zone microclimate was fabricated with micro-sensor units for heat and humidity sensing. Seed-zone micro-climate was monitored for surface seeding+full straw mulching( M,), surface seeding+half straw inulching( CK )and surface seeding with no straw mulching(CK). [Results] Field experiment showed that the constructed measurement system was suitable for registering the heat and humid dynamics within the seed-zone for no-till surface seeding. Irrigation before seeding guarantees seed germination, but the seed-zone microclimate plays a key role for seedling establishment. Straw mulching affects seed-zone microclimate significantly. Being covered straw layer reduces temperature in the day lime and maintains heat in the night. Mulching also keeps surface soil moisture from evaporating to the atmosphere. Seedling establishment rate of M, was 58.75% .which was the highest as compared with other treatments, and that for M2 was 48.15%. The lowest seed germination rate was found for CK, which was only 34.49%. Twenty days after seeding, a statistical counting was performed for seedling establishment, revealing that seedling establishment of the CK was 0. [ Conclusions J Field state seed-zone microclimate plays a decisive role in determining seed germination and seeding establishment. The constructed micro-sensor measurement system is a suitable tool for seed-zone microclimate detection. A proper agronomic tech­nology for no-till surface seeding in paddy soil requires 3 key treatments; irrigation before seeding, full seed-soil contact and appro­priate amount straw mulching. However, as no effective measure can be provided for desirable seed-soil contact, a larger seeding rate is necessary for surface seeding. [ABSTRACT FROM AUTHOR]

In many instances the basic structural units of plough layer are soil aggregates which are resulted from tillage operation and packed into layers to form the seedbed. Quantification of plough layer is limited to a few basic soil parameters, including cone index, bulk density and porosity. Soil aggregates are assessed with dry sieving. These parameters do not provide the detailed structural information of plough layer. Precision management of plough layer requires that soil structures be quantified with more parameters that are geometrically quantifiable. Quantitative method for tilled-layer soil structures was adopted; the digital images of soil structures were taken, the aggregate mass was calculated and the mass-size distributions of soil structures sampled from a plowed paddy field were studied. The tilt angle of camera was set to 30°, 45°, 60° and 90°, respectively, when taking the photos of soil structures. Soil structures were also measured manually with dry-sieving method for comparison. During the manual measurement of soil aggregates, a caliper was used and both the long and the short axes of the aggregates were measured. The dry-sieving used the nested sieves with the openings of 4, 8, 16, 32, 64 and 128 mm, respectively. Geometrical parameters of soil structures in each size range were calculated with an image-processing program developed in MatLab, including angularity, shape index and rectangle degree. Collected data for the mass-size distribution of the soil aggregates after plowing were also fitted respectively with 3 models, i.e. Weibull model, Rosin-Rammler model and Gaudin-Schuhmann model. It showed that, along with the increase of size range, both angularity and shape index increased, but rectangle degree decreased, meaning that different effects of mechanical operation were induced by different size ranges of soil structures, even though under the same plowing treatment. Detailed analysis on each size range and each tilting angle showed that photos taken with 60o tilting angle yielded the best fitting results compared with other tilting angles. The 60o tilting angle was the most suitable for camera when used for on-line soil structure monitoring. No significant difference (P>0.05) was observed between digital image processing and manual measurement, proving that the digital image processing was an accurate method to acquire mass-size distributions of soil structure. Compared with Weibull and Rosin-Bammler distribution, Gaudin-Schumann model provided the best fitting between aggregate mass and size, with the R2 of 0.98. Digital image processing discriminated soil structures in finer scales and provided a higher precision curve fitting for soil structures compared with dry-sieving method. The variation of the acquired results from dry-sieving was significant due to the large size ranges between adjacent sieve sizes. Unlike the limited methods for tilled-layer soil structure quantification, such as dry sieving, image-processing was capable of not only quantifying the geometrical parameters of soil structures, but also distinguishing and separating soil structures in finer scales, such as 5 mm size range or any other arbitrary scales. This fine scale distinction was helpful in providing more precise modeling on soil structures. The results prove that the image-processing is a powerful tool to calculate geometric parameters of soil structures and discriminate soil structural features in detail. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Nanjing Agricultural University / Nanjuing Nongye Daxue Xuebao is the property of Journal of Nanjing Agricultural University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)