Liu Guoshun

Spatial variability of soil properties in a long-term tobacco plantation in Central China.

Spatial variability in soil properties has long been observed within uniformly managed fields. Understanding the spatial characteristics of soil properties would be helpful in the development of site-specific management. Uniform management results in overapplication in areas with high nutrient levels and underapplication in areas with low nutrient levels. The objective of this study was to quantify the degree of spatial variability of soil properties. This is important to tobacco quality across flue-cured tobacco (Nicotiana tabacum) plantation fields. Fourteen soil properties were analyzed by geostatistical techniques. Soil organic matter (OM) had significantly positive correlations with active soil OM, total N (TN), available N, available phosphorus, available potassium, Cu, Fe, and Mn. Soil TN, Zn, cation exchange capacity, and silt showed strong spatial dependence, with nugget-sill ratios ranging from 3.39% to 23.43%. Other soil properties showed moderate dependence, with nugget-sill ratios of 30.87% to 49.99%. Spatial dependence ranged from 34.3 m (Zn) to 376.3 m (Mn). The OM contour map showed highest similarity with that of TN. Variography and kriging are useful tools for soil-sampling strategies and variable-rate application in site-specific farming.

Comparison of Kriging Interpolation Precision With Different Soil Sampling Intervals for Precision Agriculture

The analysis and interpretation of the spatial variability of soil properties are keystones in site-specific management. Soil sampling interval is typically used in establishing management zones for site-specific application of nutrients. Sampling intensity is an important factor that can potentially limit the accuracy of the management zone. The objectives of this study were (i) to quantify the spatial variability of soil properties across tobacco plantation fields, (ii) to select the reasonable sampling interval for eight soil variables to minimize cost and maximize evaluation accuracy, and (iii) to provide a theoretical basis for setting a reasonable sampling interval in precision agriculture. Soil samples were collected at approximately 20 m at 0- to 20-cm depth. The coordinates of each of the 111 points were recorded using global positioning system. Using a geographic information system software platform, the soil sampling points from the primary scheme were regularly deleted to create comparative schemes. The geostatistical method was used to produce distribution maps of the soil nutrients. Seven sampling points were randomly selected. The interpolation of the values of the seven soil points was compared under three sampling intervals with their actual measurements. The interpolation errors of soil organic matter and available copper were lowest in the 60-m sampling interval. In the 20-m sampling interval, alkaline hydrolyzable N, available phosphorus, available potassium, available iron, and available zinc had the least errors of interpolation. Available manganese had the least interpolation error at the 40-m sampling interval. Overall, the sampling efficiency could be further improved. The method can be applied in a practical and cost-effective manner to facilitate soil sampling.

Spatial Variability of Soil Total Nutrients in a Tobacco Plantation Field in Central China

The spatial variability of soil total nutrient levels, which may be greatly affected by parent material, plays an important role in both agriculture and environment, especially with regard to soil fertility and soil quality. Little research has been done that addresses the spatial characteristics of total nutrients. Soil samples (0–20 cm) were taken from 111 points on an approximately 20-m grid in March 2009 using a global positioning system (GPS) to define sample locations. Sixteen soil total chemical properties were analyzed by classical statistical and geostatistical methods. Soil aluminum (Al), calcium (Ca), chromium (Cr), copper (Cu), nitrogen (N), sodium (Na), silicon (Si), strontium (Sr), titanium (Ti), and vanadium (V) exhibited strong spatial dependence, with the nugget–sill ratios ranging from 3.39% (Na) to 23.53% (Si). Soil barium (Ba), iron (Fe), potassium (K), manganese (Mn), phosphorus (P), and zinc (Zn) had moderate spatial dependence, with nugget–sill ratios of 3.39% to 23.53%. The spatial correlation distances varied from 15.7 m (Zn) to 286.5 m (Cr). The clearly patchy distributions indicated that significant positive correlations among Al, Ba, Fe, K, Mn, Na, Si, Ti, and V led to strong positional similarity. The interpolated maps of the nutrients showed the spatial distributions of the soil variables, which is helpful for better understanding their spatial variability and delineating the potential agricultural management zone. The soil total nutrient distribution maps could be used as the basis for site-specific fertilizer application to improve quality and increase yield of flue-cured tobacco in the study area.

Effects of Upper Leaf Harvesting Methods on Physicochemical and Economic Properties of Flue-cured Tobacco

Flue-cured tobacco samples from Lincang tobacco growing area was used to investigate the effects of harvesting methods(upper leaves harvest completed by two primings at regular interval and by one priming) on physical character,chemical composition and economic character of the upper leaf.The results showed that single leaf weight and weight per leaf area of the top 1st-3rd leaves by one-priming were higher than those by two-priming.No significant difference was observed in the tensile strength,filling value and stem content of the top 1st-3rd leaves between the two methods.The single leaf weight,weight per leaf area,leaf thickness,tensile strength of the top 4th-6th leaves by one-priming were lower than those by two-priming.Comparing with two-priming,the leaves harvested by one-priming contained more total sugar and reducing sugar,but less nicotine,total nitrogen and Cl,the chemical composition in cured leaves was more harmonious,offered better smoking quality,but slightly lower yield and output value.

Ultramicro Structure Changes of Palisade Cell in Flue-cured Tobacco Leaf During Growth and Development

To investigate the ultramicro structure changes of palisade cell in flue-cured tobacco leaf during growth and development,the chloroplast,starch grain,osmiophilic globule and vacuole were observed by transmission electron microscope via field experiments.The results showed that the chloroplasts in palisade cell was in developing and photosynthesis began when leaf was 10 cm in length;small vacuoles had fused into a single large central vacuole when leaf was 20 cm in length;at 50 cm leaf length,the structure of chloroplasts matured,and cells entered a florescent stage,in which synthesis was dominant.After tobacco leaf reached 60 cm in length,chloroplasts gradually degraded along with rapid enlarging and increase of the accumulated starch grains,and the osmiophilic globules increased obviously.In ripe leaf,plentiful starch grains and osmiophilic globules accumulated in chloroplast.

Application of Principal Component Analysis and Cluster Analysis in Tobacco Quality Evaluation

Combining with appearance quality and chemical analysis,the quality of 45 samples from Xinyang tobacco growing area in Henan was evaluated by principal component analysis and cluster analysis.The results showed that the appearance quality of samples was fine in general,while they were slightly weak in oil,colority,chromatism and leaf surface uniformity.The contents of the majority of chemical components were up to the standard of quality tobacco leaf,though total nitrogen and K were lower and starch was slightly higher.The samples were divided into 3 groups by cluster analysis,which integrated 8 appearance indexes with 8 chemical indexes and rejected repeated information among the 16 indexes.