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1.
Precision agriculture may offer sugarcane growers a management system that decreases costs and maximizes profits, while minimizing
any potential negative environmental impact. The utility of variable-rate (VR) lime application in the initial production
year (plant cane) of a 3-year sugarcane crop cycle was investigated at three locations planted to the cultivar LCP 85–384
for a total of nine site-years. A conventional, uniform-rate (UR) lime application method was compared to a VR application
method and a no-lime control. Prior to lime application, soil samples (0–200 mm) were taken on a 0.4 ha grid to produce VR
application maps. Soil samples were also taken after each crop of the 3-year production cycle to determine effects of lime
application on soil properties. The combined results showed that neither the UR nor VR lime application method consistently
improved cane or sugar yields over the no-lime control. Cane and sugar yields at Naquin Farms (NF) were increased with both
the UR and VR methods, with the UR method having a slight advantage. At St. Louis Plantation (SLP), only the VR method in
the first-ratoon crop increased cane and sugar yields and there were no yield differences due to lime application at Ellendale
Plantation (EP). At NF and SLP, application of lime in the plant-cane crop increased soil pH and available phosphorus over
the 3-year production cycle. At EP, lime application did not influence any of the soil properties measured. The failure to
get a yield response from lime application at SLP and EP may have been due to the fact that fertility levels at planting were
already greater than those at NF and the nitrogen fertilizer rates used by the grower at EP were higher than those at either
SLP or NF. This may have obscured any positive yield effects that would be realized from increased nutrient availability.
It is also possible that multiple VR lime applications will be required over a number of crop cycles to stabilize soil pH
levels before a consistent positive effect on cane and sugar yields is observed with VR application. This possibility will
be investigated in future studies. 相似文献
2.
Grid sampling allows a variable rate of lime to be applied and has been marketed as a cost saver to producers. However, there is little research that shows if this precision application is profitable or not. Previous research on variable-rate lime has considered only a small number of fields. This paper uses soil sampling data from 111 fields provided by producers in Oklahoma and Kansas. The 5-year average net present values are compared between variable-rate and uniform-rate lime for grain-only wheat production, dual-purpose wheat grain and forage production, and a wheat–soybean rotation. Sensitivity analysis was done for varying grain prices as well as grain yield potential. When using historical average yields and recent prices for Oklahoma, variable rate was not profitable on average for these 111 fields for either a grain-only, dual-purpose, or wheat–soybean production. However, when yield or prices were above average, variable rate was profitable. Thus, variable rate liming can be profitable for these fields, but it requires either above average yields, a high value crop, or above average prices.
相似文献3.
Core soil sampling followed by laboratory analysis is the traditional method used to map soil pH prior to variable rate application (VRA) of lime on cropland. A recently developed automated soil sampling system capable of measuring soil pH on-the-go has significantly increased sampling resolution. However, adoption of such systems must be justified economically. This paper presents a method for assessing the economic benefit from automated mapping of soil pH prior to variable rate lime application. In this work, geostatistical, agronomic, and economic methods were used to generate a comprehensive numerical model for quantitative assessment of the net return over cost of liming for different lime management strategies. The strategies included: automated pH mapping, manual grid soil sampling, and whole field sampling used in combination with either variable or fixed rate liming. The model was demonstrated using a simulated field with known average pH and semivariogram model. The analysis showed the largest benefit ($6.13ha–1year–1) from using VRA with automated soil pH mapping versus VRA based on 1ha (2.5acres) manual grid point sampling for the selected simulated field conditions. A sensitivity analysis demonstrated that for a wide range of field conditions and crop prices, VRA plus automated mapping promises higher relative benefits than VRA based on either manual grid point or grid cell sampling. 相似文献
4.
Antoni Magri Harold M. Van Es Michael A. Glos William J. Cox 《Precision Agriculture》2005,6(1):87-110
Several potential sources of information exist to support precision management of crop inputs. This study evaluated soil test data, bare-soil remote sensing imagery and yield monitor information for their potential contributions to precision management of maize (Zea mays L.). Data were collected from five farmer-managed fields in Central New York in 1999, 2000, and 2001. Geostatistical techniques were used to analyze the spatial structure of soil fertility (pH, P, K, NO3 and organic matter content) and yield variables (yield, hybrid response and N fertilization response), while remote sensing imagery was processed using principal component analysis. Geographic information system (GIS) spatial data processing and correlation analyses were used to evaluate relationships in the data. Organic matter content, pH, P, and K were highly consistent over time and showed high to moderate levels of spatial autocorrelation, suggesting that grid soil sampling at 2.5–5.5ha scale may be used as a basis for defining fertility management zones. Soil nitrate levels were strongly influenced by seasonal weather conditions and showed low potential for site-specific N management. Aerial image data were correlated to soil organic matter content and in some cases to yield, mainly through the effect of drainage patterns. Aerial image data were not well correlated with soil fertility indicators, and therefore were not useful for defining fertility management zones. Yield response to hybrid selection and nitrogen fertilization rates were highly variable among years, and showed little justification for site-specific management. In conclusion, we recommend grid-based management of lime, P, and K, but no justification existed within our limited study area for site-specific N or hybrid management. 相似文献
5.
石灰用量对水稻油菜轮作区土壤酸度、土壤养分及作物生长的影响 总被引：3，自引：0，他引：3
【目的】我国南方稻油轮作区土壤酸化趋势日趋严重,降低了作物产量。研究酸性土壤施用石灰对土壤养分及作物生长的影响,明确土壤速效养分、产量与作物养分吸收量对土壤pH的响应关系,为水田两熟区酸化土壤改良提供理论依据。【方法】2015—2018年在江西进贤县选择pH 4.5的水稻土,以熟石灰作为酸性土壤改良剂,开展田间定位试验。通过实验室模拟,计算出获得不同土壤pH情况下的熟石灰用量,试验设6个土壤pH梯度,分别为4.5、5.0、5.6、6.3、6.8、7.3,2015年匀地一年,为保证各处理土壤pH与匀地一年后实测pH基本一致,以一年为周期用熟石灰进行定量调整。【结果】（1）随着石灰用量和土壤pH的增加,土壤速效氮含量呈先增加后降低的趋势、交换性钙、交换性镁含量显著增加,土壤速效钾、有效磷含量显著降低;（2）随着石灰用量和土壤pH的增加,作物产量呈先增加后降低的趋势。土壤pH 6.4时（相当于6 145 kg·hm -2熟石灰用量）油菜产量达到最高,较土壤pH 4.5处理增加了202.2%;土壤pH 6.8时（相当于7 474 kg·hm -2熟石灰用量）,水稻产量达到最高,较土壤pH 4.5处理增加了61.2%。油菜、水稻产量降低50%时的酸害阈值分别为4.7、4.2;（3）土壤pH显著影响作物养分吸收量。随着熟石灰用量的增加,油菜氮磷钾吸收量呈先增加后降低的趋势。2016—2018年油菜氮磷钾吸收量与不施石灰处理相比,施石灰处理平均增幅分别为59.5%—181.4%、36.2%—188.8%、65.7%—198.9%;水稻氮磷钾吸收量呈先增加后降低的趋势,在pH 6.8左右水稻氮磷钾吸收量最大。2016—2018年水稻氮磷钾吸收量与不施石灰处理相比,施石灰处理平均增幅分别为11.1%—88.6%、13.5%—68.5%、9.7%—66.1%。【结论】施用熟石灰的情况下,随着土壤pH升高,土壤速效氮、交换性钙镁等含量增加,提高了产量,促进了作物对氮磷钾养分的吸收。在本试验条件下,稻油轮作区酸性土壤（pH 4.5）施用熟石灰的最佳用量为6 500 kg·hm -2左右,改良土壤的目标为pH 6.5左右,可获得我国南方稻油轮作区的作物稳定高产。 相似文献
6.
7.
YAN ZhiHao HU ZhiHua WANG ShiChao HUAI ShengChang WU HongLiang WANG JinYu XING TingTing YU XiChu LI DaMing LU ChangAi 《中国农业科学》2019,52(23):4285-4295
【Objective】Soil acidification is becoming more and more serious, which reducing crop yield in rice-rape rotation system of southern of China. In this study, the effects of lime application on soil nutrients and crop growth in acidic soil were studied, and the response relationship between soil available nutrients, yield and crop nutrient uptake to soil pH was clarified, so as to provide theoretical basis for the improvement of acidified soil in paddy fields. 【Method】 From 2015 to 2018, the paddy field with soil pH 4.5 was selected in Jinxian county, Jiangxi province, and hydrated lime was used as acid soil modifier. Through laboratory simulation, the amount of hydrated lime under different soil pH values was calculated. Then field experiments were carried out with six soil pH gradients of pH 4.5, pH 5.0, pH 5.6, pH 6.3, pH 6.8, and pH 7.3. In 2015, in order to ensure that the pH value of the treated soil was basically consistent with the measured pH value, one year after the soil was uniformly planted, the hydrated lime was used for quantitative adjustment with a period of one year. 【Result】 (1) With the amounts of lime and soil pH increase, the contents of soil available nitrogen increased first and then decreased, the content of soil exchangeable Ca 2+ and exchangeable Mg 2+ increased significantly, and the content of soil available potassium and available phosphorus decreased significantly. (2) With the increase of lime contents and soil pH, crop yield first increased and then decreased. At pH 6.4 (equivalent to the amount of 6 145 kg·hm -2hydrated lime), the yield of rape reached the highest; compared with pH 4.5, the yield increased by 202.2%. At pH 6.8 (equivalent to the amount of 7 474 kg·hm -2hydrated lime), the rice yield reached the highest; compared with pH 4.5, the yield increased by 61.2%. When the yield was reduced by 50%, the soil pH thresholds of rape and rice were 4.7 and 4.2, respectively. (3) Soil pH significantly affected crop nutrient uptake content. With the increase of the amount of hydrated lime, the nitrogen, phosphorus and potassium uptake contents in rape increased first and then decreased. The average increase of nitrogen, phosphorus and potassium uptake contents in rape from 2016 to 2018 was 59.5%-181.4%, 36.2%-188.8% and 65.7%-198.9%, respectively. The nitrogen, phosphorus and potassium uptake contents in rice first increased and then decreased. The uptake content of rice was the highest at pH 6.8. Compared with that without lime application the average increase of nitrogen, phosphorus and potassium uptake of rice from 2016 to 2018 was 11.1%-88.6%, 13.5%-68.5% and 9.7%-66.1%, respectively.【Conclusion】Under the application of lime conditioner, the contents of soil available nitrogen and exchangeable Ca 2+ and exchangeable Mg 2+ were increased with the increase of soil pH, which promoted the uptake of nitrogen, phosphorus and potassium nutrients of crops and increased the crop yield. Under the experiments conditions, the optimal dosage of lime in acid soil (pH 4.5) of rice -rape rotation system was about 6 500 kg·hm -2, which could obtain stable and high yield of crops in rice-rape rotation system of southern China. 相似文献
8.
Research is lacking on the long-term impacts of field-scale precision agriculture practices on grain production. Following more than a decade (1993–2003) of yield and soil mapping and water quality assessment, a multi-faceted, ‘precision agriculture system’ (PAS) was implemented from 2004 to 2014 on a 36-ha field in central Missouri. The PAS targeted management practices that address crop production and environmental issues. It included no-till, cover crops, growing winter wheat (Triticum aestivum L.) instead of corn (Zea mays L.) for field areas where corn was not profitable, site-specific N for wheat and corn using canopy reflectance sensing, variable-rate P, K and lime using intensively grid-sampled data, and targeting of herbicides based on weed pressure. The PAS assessment was accomplished by comparing it to the previous decade of conventional, whole-field corn-soybean (Glycine max L.) mulch-tillage management. In the northern part of the field and compared to pre-PAS corn, relative grain yield of wheat in PAS was greatly improved and temporal yield variation was reduced on shallow topsoil, but relative grain yield was reduced on deep soil in the drainage channel. In the southern part of the field where corn remained in production, PAS did not lead to increased yield, but temporal yield variation was reduced. Across the whole field, soybean yield and temporal yield variation were only marginally influenced by PAS. Spatial yield variation of all three crops was not altered by PAS. Therefore, the greatest production advantage of a decade of precision agriculture was reduced temporal yield variation, which leads to greater yield stability and resilience to changing climate. 相似文献
9.
Remote sensing of soybean canopy as a tool to map high pH, calcareous soils at field scale 总被引：1，自引：0，他引：1
Soybean (Glycine max Merr.) is extensively grown in areas of the US Corn Belt where soils often range from relatively acid (pH < 6) to alkaline,
calcareous. Iron availability decreases with increase in pH, consequently, soybean can suffer from iron deficiency chlorosis
on high pH, calcareous areas of the field. The extent of those areas sometimes can be significant, but they often occur in
complex and discontinuous patterns. The objective of the research was to explore how remote sensing of soybean canopies and
GIS technologies could be used to map and quantitatively describe the extent of high pH, calcareous soils at field scale.
Aerial images that consisted of visible red, green, blue, and near infrared bands were used to calculate green normalized
difference vegetative index (GNDVI) and to guide plant and soil sampling at 10 fields during 2003 and 2004 growing seasons.
Ten to 18 sampling areas were selected on each field to include a wide range in GNDVI values. Soil samples were analyzed for
pH and calcium carbonate equivalent (CCE). Plant samples were used to estimate grain yields. Soil pH and CCE were significantly
correlated with GNDVI values in eight and seven sites, respectively. A previously developed alkalinity stress index (ASI),
which combines pH and CCE in one value, was significantly related to GNDVI at all 10 sites. Remote sensing of soybean canopy
was shown to be a promising tool that can be used to quantitatively describe distribution of alkaline soils at field scale. 相似文献
10.
Thompson A. N. Shaw J. N. Mask P. L. Touchton J. T. Rickman D. 《Precision Agriculture》2004,5(4):345-358
Characterizing the spatial variability of nutrients facilitates precision soil sampling. Questions exist regarding the best technique for directed soil sampling based on a priori knowledge of soil and crop patterns. The objective of this study was to evaluate zone delineation techniques for Alabama grain fields to determine which method best minimized the soil test variability. Site one (25.8 ha) and site three (20.0 ha) were located in the Tennessee Valley region, and site two (24.2 ha) was located in the Coastal Plain region of Alabama. Tennessee Valley soils ranged from well drained Rhodic and Typic Paleudults to somewhat poorly drained Aquic Paleudults and Fluventic Dystrudepts. Coastal Plain soils ranged from coarse-loamy Rhodic Kandiudults to loamy Arenic Kandiudults. Soils were sampled by grid soil sampling methods (grid sizes of 0.40 ha and 1 ha) consisting of: (1) twenty composited cores collected randomly throughout each grid (grid-cell sampling) and, (2) six composited cores collected randomly from a 3×3m area at the center of each grid (grid-point sampling). Zones were established from (1) an Order 1 Soil Survey, (2) corn (Zea mays L.) yield maps, and (3) airborne remote sensing images. All soil properties were moderately to strongly spatially dependent as per semivariogram analyses. Differences in grid-point and grid-cell soil test values suggested grid-point sampling does not accurately represent grid values. Zones created by soil survey, yield data, and remote sensing images displayed lower coefficient of variations (%CV) for soil test values than overall field values, suggesting these techniques group soil test variability. However, few differences were observed between the three zone delineation techniques. Results suggest directed sampling using zone delineation techniques outlined in this paper would result in more efficient soil sampling for these Alabama grain fields. 相似文献
11.
酸性土壤施用石灰提高作物产量的整合分析 总被引：8，自引：2，他引：6
【目的】施用石灰是改良土壤酸度获得作物增产的传统而有效的方法之一,整合分析石灰增加作物产量的效应和原因,对科学合理施用石灰维持作物高产提供指导。【方法】收集已公开发表有关石灰改良酸性土壤的文献数据,建立土壤p H和作物产量/生物量数据库。分析土壤初始p H(3.1—6.6)、作物类型(粮食作物、经济作物)、石灰施入量(750、750—1 500、1 500—3 000、3 000—6 000、6 000 kg·hm-2)和石灰类型(生石灰、熟石灰、石灰石粉)下,作物的增产率。【结果】与不施石灰相比,酸性土壤上施用石灰可提高作物产量,增产幅度为2%—255%,粮食类作物和经济类作物增产率分别为42%和47%,其中粮食类作物增产率大小排序:玉米(149%)高粱(142%)麦类(55%)豆类(32%)水稻(4%)薯类(2%),经济类作物增产率排序:蔬菜(255%)牧草(89%)油菜(26%)水果(23%)烟草(7%)。施用石灰作物增产率随土壤初始p H的升高呈先升高后降低趋势:当p H为4.3时,增产效果最好,达99%;p H 5.8以上出现减产。在常见土壤酸性范围(p H 4.5—5.5),石灰用量以3 000—6 000 kg·hm-2最佳,增产率达55%—173%。熟石灰的增产效果(100%)要优于生石灰(32%)和石灰石粉(64%)。施用石灰提高土壤p H和交换性钙含量、降低交换性铝含量,是作物增产的主要原因,且当交换性钙为6.2 cmol·kg~(-1)时增产率最大,也证实改良土壤酸度时需要中等石灰用量。【结论】酸性土壤添加石灰对蔬菜和玉米的增产效果最好,并优先选用熟石灰。石灰用量以3 000—6 000 kg·hm-2为宜,在p H大于5.8时不宜施用,即酸性土壤改良目标值为p H 5.8。 相似文献
12.
文章针对黑龙江省耕地黑土发生酸化的现象,分别采取不同的治理措施,发现在白浆化黑土、草甸黑土中施用有机肥料和草木灰、生石灰后大豆株高、荚数均有增加;白浆化黑土中施用有机肥料增产效果最显著,与对照相比增产428.4kg.hm-2,增产百分率为19.87%;其次是施用草木灰,增产14.81%。施用生石灰增产效果不明显,在草甸黑土中施用草木灰时大豆增产效果要好于生石灰,与对照处理相比,施用草木灰处理增产7.77%。施用有机肥料和草木灰、生石灰都能使土壤的pH提高,对治理土壤酸化具有一定意义。 相似文献
13.
吉林省大豆种植区土壤的机械组成、pH值及营养元素与产量的关系 总被引：1，自引：0，他引：1
试验研究了吉林省大豆种植区土壤的机械组成、pH值及主要营养元素与产量的关系。结果表明：粘粒、粉粒与大豆产量具有显著相关关系(r=0．734，r=0．788)。大豆生长理想的土壤质地条件为粉砂粘壤土和粘壤土，土壤中的粘粒含量为15％～25％、粉砂粒含量为25％～45％有利于大豆的高产；土壤pH值与大豆产量具有显著负相关关系(r=-0．834)，但土壤pH值为5．5～6．5有利于大豆的高产；土壤碱解氮与产量具有显著正相关关系(r=0．899)，碱解氮为80～140mg／kg大豆的产量较高；土壤速效磷和钾与大豆产量无显著相关性；大豆种植区养分有效性的发挥与土壤的pH值、机械组成及氮磷钾的比率等有一定的关系。 相似文献
14.
In Indiana, variable rate application (VRA) of lime is often considered a good place to start site-specific management (SSM). This is because soil pH is one of the most variable of manageable soil characteristics in the state, the availability of essential nutrients is closely related to soil pH, and because spreaders can be retrofitted relatively inexpensively to do VRA. The objective of this study is to evaluate the profitability of VRA for lime as a stand-alone activity. The methodology involves a spreadsheet model using corn and soybean pH response functions estimated with small plot data. The overall results indicate increased annual returns to corn and soybean production with site-specific pH management strategies. On average, SSM with agronomic recommendations provides an increased annual return of $7.24 per hectare (ha) (+1.78%). SSM with the economic decision rule provides an average increase in annual return of $19.55 ha–1 (+4.82%). Information strategy, which uses site-specific information to determine the economically optimal uniform rate of lime, provides an average increase in annual return of $14.38 ha–1 (+3.54%). 相似文献
15.
Soil phosphorus (P) concentrations above certain critical thresholds are a problem in many areas leading to its transport
into surface and ground waters. Site-specific nutrient applications and the development of nutrient management plans for farms
would help to optimize nutrient applications, meet crop requirements and take into consideration current soil nutrient status.
In Northern Ireland, high concentrations of soil P are common, whereas low concentrations of soil potassium (K) and sulphur
(S) have been reported in many silage fields. This study used grid and transect soil sampling to measure within- and between-field
spatial variation in soil Olsen-P status across a 50-ha permanent grassland site used for silage production. Soil phosphorus
indices ranged from Index 1 to Index 4 within single fields. The spatial patterns of soil P across fields suggested that there
was scope for site-specific P fertilizer applications, with variable quantities of P being applied to different fields and
within individual fields. Site-specific nutrient management has the potential to reduce excess P applications in some areas
and avoid deficiencies in others, thereby minimizing environmental problems and optimizing yield. 相似文献
16.
Ntsikane Maine James Lowenberg-DeBoer Wilhelem Thomas Nell Zerihun Gudeta Alemu 《Precision Agriculture》2010,11(5):448-463
The response of maize (Zea mays) to banded variable-rate nitrogen (N) application over a period of 3 years (2002/3–2004/5) is analyzed. The experimental
design alternated variable-rate (VR) and single-rate (SR) applications of N. The yield monitor data were spatially autocorrelated
and therefore were analyzed with spatial regression methods. The baseline spatial regression model defined in this study showed
that the VR treatment, treatment by year and treatment by management zone were statistically significant. Sensitivity tests
were applied; the first showed that VR treatment had a yield advantage when soil depth was greater than the field average
of 174 cm. The second test showed that the VR N rates applied were close to those that would maximize profit. Partial budgeting
indicates that benefits from VR vary from year to year, but in this test VR was slightly more profitable than uniform rate
application. Economic sensitivity testing indicates that farm size and the price of maize are the key factors in the profitability
of VR N. 相似文献
17.
Wang Dechun Prato Tony Qiu Zeyuan Kitchen Newell R. Sudduth Kenneth A. 《Precision Agriculture》2003,4(1):35-52
Variable Rate Technology (VRT) has the potential to increase crop yields and improve water quality relative to Uniform Rate Technology (URT). The effects on profitability and water quality of adopting VRT for nitrogen (N) and lime were evaluated for corn production on four claypan soil fields in north central Missouri under average to better than average weather conditions. Variable N and lime rates were based on measured topsoil depth and soil pH, respectively. VRT rates were compared to two different uniform N applications (URT-Nl based on the topsoil depth within these claypan soil fields, and URT-N2 based on a typical N rate for corn production in this area). Expected corn yield was predicted based on topsoil depth, soil pH, N rate, and lime rate. Water quality benefits of VRT relative to URT were evaluated based on potential leachable N. Sensitivity analyses were performed using simulated topsoil data for topsoil depth and soil pH. Results showed that VRT was more profitable than URT in the four sample fields under URT-N1, and in two of the four fields under URT-N2. Greater variation in topsoil depth and soil pH resulted in higher profitability and greater water quality benefits with VRT. Results support adoption of VRT for N and lime application for other claypan soil fields with characteristics similar to those in the fields used in this study. 相似文献
18.
For yield based site-specific management to be successful in fields with crop rotations, changes in management zones between
crops must be determined. The study objectives were to determine if yield classes change between crops within a rotation and
whether soil properties can predict the yield classes or the year-to-year changes. A percentile classification method was
used to categorize yearly soybean (Glycine max) and rice (Oryza sativa) yield in two fields with soybean-rice-soybean rotations into low, medium and high yield classes. There was little agreement
in yield classifications between years. Yield class based on soil properties was predicted accurately by linear discriminant
analysis in Field 1 20–67% of the time and in Field 2 13–83% of the time. Predictions in Field 1 were based on soil available
Mg and P, elevation and the deep soil apparent electrical conductivity (ECa). Predictions in Field 2 were based on soil texture, soil available P, K and Mg, and pH. The linear discriminant analysis
was also able to predict year-to-year changes in yield class. Changes in class in Field 1 could be predicted by total soil
C and N, silt, and soil available Mg and P depending on the year. Soil texture, soil available P, K and Mg, total soil C and
pH, elevation and deep soil ECa predicted yield changes in Field 2 depending on the year. The results of this study indicate only limited success at management
zone definition in a soybean-rice rotation. Further investigation is needed with other crop rotation sequences to verify the
findings of this study. 相似文献
19.
Variable-rate fertilizer application is often based on grid soil sample data from a single year of data in an annual crop rotation. The objectives of this study were to determine if crop history influences spatial dependence (the degree of spatial variability) of nutrients in a rotation including both annual crops and alfalfa, and to compare grid-based and topography-based sampling strategies for representing within-field nutrient levels. A site in the Red River Valley of North Dakota was observed over three years from 1994–1996. The site was divided into one field of continuous alfalfa (Medica sativa L.) and an adjacent field seeded to spring wheat (Triticum aestivum L.) in 1994, barley (Hordeum vulgare L.) in 1995 and alfalfa in 1996. Samples were taken from a 16.2-ha site each fall in a 33-m grid and analyzed for NO3-N, P, SO4-S and Cl. Topography was determined by measuring elevation in a 33-m grid with a laser-surveying device. Spatial dependence was determined by calculating the semivariogram and using regression analysis to assess the relationship between the semivariogram and the semivariogram model. Spatial dependence of NO3-N and P was strongest following spring wheat and barley, while spatial dependence for SO4-S and C1 was strongest for vigorous stands of alfalfa. When the continuous alfalfa stand declined following winter kill, NO3-N and P spatial dependence intensified. Topography based sampling was correlated with the 33-m grid by giving each 33-m sampling location its value as directed by a topography sampling, then correlating that topography based value with the original 33-m sampling value. Topography-based sampling was correlated with the 33-m sampling grid for all nutrients following spring wheat and barley, but not in continuous alfalfa until the stand began to decline in vigor. Following alfalfa seeding in the annual crop field, topography relationships with NO3-N and P decreased, while topography relationships with SO4-S and Cl increased. Topography samplings of sulfate-S and chloride were most highly correlated to 33-m grid values in vigorous alfalfa. Lack of NO3-N spatial dependence in the vigorous alfalfa stands suggests that a composite or field average soil test might be sufficient to provide soil NO3-N information under similar conditions. 相似文献
20.
【目的】探究不同磷肥对土壤磷素形态转化及小麦磷素吸收利用效率的影响,为土壤-磷肥-作物体系磷肥精准匹配及高效利用提供理论依据。【方法】在砂姜黑土和红壤上设置不施磷（CK）、施用过磷酸钙（SSP）、钙镁磷肥（FMP）、磷酸二铵（DAP）、重过磷酸钙（TSP）和聚磷酸铵（APP）6个处理,研究小麦拔节期和开花期根际与非根际土壤中磷库转化特征及其与植株体内磷素累积利用的关系。【结果】砂姜黑土施用磷肥后土壤有效磷含量提高194%—662%,不同磷肥处理小麦根际土壤中有效磷含量为APP>TSP>DAP>FMP>SSP>CK处理。施用磷肥显著提升了小麦拔节期和开花期砂姜黑土中H2O-P和NaHCO3-Pi含量,降低Residual-P含量,其中H2O-P和NaHCO3-Pi含量与土壤有效磷含量呈显著正相关,TSP和APP处理在小麦拔节期对NaHCO3-Pi含量提升幅度最大,分别较不施磷提升了41.0和36.0 mg·kg-1。红壤施用磷肥后根际土壤有效磷含量提高84%—791%,其中DAP和TSP处理的土壤有效磷含量显著高于其他磷肥处理,红壤中根际土壤NaHCO3-P... 相似文献