Selection of Optimum Vegetative Indices for the Assessment of Tobacco Float Seedlings Response to Fertilizer Management

The experiment sought to establish the vegetative indices for assessing tobacco float seedling varieties’ response to different fertilizer rates. A factorial design, with 3 variety 4 fertilizer management treatments, was used. The N : P : K treatments were applied at 7, 21, and 35 days after sowing, while N treatments were applied at 42 days. Radiometric measurements were taken at 49, 56, 64, and 79 days after sowing on 8 tray plots, using a multispectral radiometer. Mature seedling samples were harvested at day 79 and stem lengths were determined before processing for total N analysis. All the five channels of the radiometer, the NDVI, and the SRI had a strong relationship with fertiliser rate. Both the NDVI and SRI for T66 were greater () than those for KRK26 and KE1. The SRI had a stronger relationship with seedling dry mass, seedling count/tray, and stem length than the NDVI. The NDVI also showed a stronger relationship with total N than the SRI. The minimum threshold SRI and NDVI values and optimum growth (100% fertilser) were 0.72 and 6.1. This information is useful in identifying and estimating tobacco seedbed area and seedling vigour using remote sensing and, therefore, is important in forecasting potential tobacco crop area and yield.</jats:p

Spectral Indices: In-Season Dry Mass and Yield Relationship of Flue-Cured Tobacco under Different Planting Dates and Fertiliser Levels

This experiment investigated the relationship between tobacco canopy spectral characteristics and tobacco biomass. A completely randomized design, with plantings on the 15th of September, October, November, and December, each with 9 variety × fertiliser management treatments, was used. Starting from 6 weeks after planting, reflectance measurements were taken from one row, using a multispectral radiometer. Individual plants from the other 3 rows were also measured, and the above ground whole plants were harvested and dried for reflectance/dry mass regression analysis. The central row was harvested, cured, and weighed. Both the maximum NDVI and mass at untying declined with later planting and so was the mass-NDVI coefficient of determination. The best fitting curves for the yield-NDVI correlations were quadratic. September reflectance values from the October crop reflectance were statistically similar (P&gt;0.05), while those for the November and the December crops were significantly different (P&lt;0.05) from the former two. Mass at untying and NDVI showed a quadratic relationship in all the three tested varieties. The optimum stage for collecting spectral data for tobacco yield estimation was the 8–12 weeks after planting. The results could be useful in accurate monitoring of crop development patterns for yield forecasting purposes.</jats:p

Remote Sensing Applications in Tobacco Yield Estimation and the Recommended Research in Zimbabwe

Tobacco crop area and yield forecasts are important in stabilizing tobacco prices at the auction floors. Tobacco yield estimation in Zimbabwe is currently based on statistical surveys and ground-based field reports. These methods are costly, time consuming, and are prone to large errors. Remote sensing can provide timely information on crop spectral characteristics which can be used to estimate crop yields. Remote sensing application on agriculture in Zimbabwe is still very limited. Research should focus on identifying suitable reflectance indices that are related to tobacco growth and yield. Varietal yield response to fertiliser and planting dates as well as suitable temporal windows for spectral data collection should be identified. The challenges of the different tobacco land sizes have to be overcome by identifying suitable satellite platform, with sufficient spectral resolution to separate the tobacco crop from the adjacent competing crops and noncrop vegetative surfaces. The identified suitable index should be strongly correlated with tobacco in season dry mass and yield. The suitable vegetative indices can be employed in establishing tobacco cropped area and then apply the long-term area yield relationship from government and nongovernmental statistical departments to estimate yield from remote sensing derived cropped area.</jats:p

Remote sensing applications in tobacco yield estimation and the recommended research in Zimbabwe

Tobacco crop area and yield forecasts are important in stabilizing tobacco prices at the auction floors. Tobacco yield estimation in Zimbabwe is currently based on statistical surveys and ground-based field reports.These methods are costly, time consuming, and are prone to large errors. Remote sensing can provide timely information on crop spectral characteristics which can be used to estimate crop yields. Remote sensing application on agriculture in Zimbabwe is still very limited. Research should focus on identifying suitable reflectance indices that are related to tobacco growth and yield. Varietal yield response to fertiliser and planting dates as well as suitable temporal windows for spectral data collection should be identified. The challenges of the different tobacco land sizes have to be overcome by identifying suitable satellite platform, with sufficient spectral resolution to separate the tobacco crop fromthe adjacent competing crops and noncrop vegetative surfaces.The identified suitable index should be strongly correlated with tobacco in season dry mass and yield. The suitable vegetative indices can be employed in establishing tobacco cropped area and then apply the long-term area yield relationship from government and nongovernmental statistical departments to estimate yield from remote sensing derived cropped area.,Tobacco Research Board and Kutsaga Research Statio

Optimizing grass mulch application rate in flue cured tobacco float seedlings for the control of salt injury and improvement of seedling quality

In the tobacco seedling production system, water moves up by capillary action from the water bed to the surface where it evaporates. Salts that accumulate after evaporation cause injury of plants. Some of the well noted effects include ion toxicity and reduction in seed germination, plant growth, and reduced crop yields. An experiment was carried out at Kutsaga Research Station in Harare to optimize mulch quantities in tobacco float seedlings for the control of salt injury and improvement of seedling quality. Vlei grass mulch was applied on experimental plots at 0 kg/ m2 (0 % mulch), 58 kg/ m2 (50 % mulch), 1.16 kg/ m2 (100 % mulch) and 1.74 kg/ m2 (150 % mulch) in two seasons; 2012 and 2013 in July and in August. Germination percentage, survival counts and seedling damage assessments were measured at 7, 21 and 28 days after sowing (d.a.s). Growing media samples were collected for electrical conductivity (EC) and pH measurements at the same time. In both the July and the August sowings, germination increased with increasing mulch levels. The highest germination percentage (80%) was attained in August at the 100% mulch covering. Growing media pH did not significantly differ under different mulch levels but increased with days after sowing in both July and August. Media EC increased with days after sowing, generally, but lethal levels were reached on August sown seedlings at 0% and 50 % mulch rate. Seedling stem diameter increased with mulch rate in both sowing times, with the maximum attained at 100 % mulch rate. Stem height decreased with increasing mulch rate in the July sown, while the reverse was true in the August sown, where the maximum stem height was attained at 100 % mulch rate. The results show that mulch at the rate of 1.16 kg/ m2 (100 % mulch) is required for salt injury control in the floatbed for the improvement of seedling survival and seedling quality, measured as stem height and stem thickness during the warmer times of the seedbed seaso

Spectral indices: in-season dry mass and yield relationship of flue-cured tobacco under different planting dates and fertiliser levels

This experiment investigated the relationship between tobacco canopy spectral characteristics and tobacco biomass. A completely randomized design, with plantings on the 15th of September, October, November, and December, each with 9 variety × fertiliser management treatments, was used. Starting from6 weeks after planting, reflectance measurements were taken fromone row, using a multispectral radiometer. Individual plants from the other 3 rows were also measured, and the above ground whole plants were harvested and dried for reflectance/dry mass regression analysis. The central row was harvested, cured, and weighed. Both the maximum NDVI and mass at untying declined with later planting and so was the mass-NDVI coefficient of determination. The best fitting curves for the yield-NDVI correlations were quadratic. September reflectance values from the October crop reflectance were statistically similar (𑃠> 0.05), while those for the November and the December crops were significantly different (𑃠< 0.05) fromthe former two.Mass at untying andNDVI showed a quadratic relationship in all the three tested varieties.Theoptimum stage for collecting spectral data for tobacco yield estimation was the 8–12 weeks after planting.The results could be useful in accurate monitoring of crop development patterns for yield forecasting purposes.,Tobacco Research Board and Kutsaga Research Statio

Assessing the spectral separability of flue cured tobacco varieties established on different planting dates and under varying fertilizer management levels

The NDVI was used to discriminate tobacco variety, assess fertilizer levels, and determine the impact of planting date on separating crops. A split plot design with four planting dates, September, October, November, and December, as main plots, variety as subplot, and fertilizer treatments as sub-subplots was used. Radiometric measurements were taken from 5m × 5m sampling plots, using a multispectral radiometer. The September, October, and November crops had significant variety x fertilizer treatment differences (ð¹ 0.05) NDVI values and these were greater (ð¹ < 0.5) than those for K E1. The 100% and the 150% fertilizer treatments were similar (ð¹ > 0.05) and both were greater (ð¹ < 0.05) than the 50% fertilizer treatments. All of the fertilizer and variety treatments at the December planting dates had similar reflectance characteristics (𑃠> 0.05), which were lower (𑃠< 0.05) than the September and October planting dates.The results showed that planting dates, varieties, and fertilizer levels could be distinguished using spectral data. Weeks 10-11 and 15 after the start of the experiment were optimal for separating the planting date effect

Spectral indices: in-season dry mass and yield relationship of flue-cured tobacco under different planting dates and fertiliser levels

This experiment investigated the relationship between tobacco canopy spectral characteristics and tobacco biomass. A completely randomized design, with plantings on the 15th of September, October, November, and December, each with 9 variety × fertiliser management treatments, was used. Starting from6 weeks after planting, reflectance measurements were taken fromone row, using a multispectral radiometer. Individual plants from the other 3 rows were also measured, and the above ground whole plants were harvested and dried for reflectance/dry mass regression analysis. The central row was harvested, cured, and weighed. Both the maximum NDVI and mass at untying declined with later planting and so was the mass-NDVI coefficient of determination. The best fitting curves for the yield-NDVI correlations were quadratic. September reflectance values from the October crop reflectance were statistically similar (𑃠> 0.05), while those for the November and the December crops were significantly different (𑃠< 0.05) fromthe former two.Mass at untying andNDVI showed a quadratic relationship in all the three tested varieties.Theoptimum stage for collecting spectral data for tobacco yield estimation was the 8–12 weeks after planting.The results could be useful in accurate monitoring of crop development patterns for yield forecasting purposes.,Tobacco Research Board and Kutsaga Research Statio

Selection of Optimum Vegetative Indices for the assessment of tobacco float seedlings response to fertilizer management

The experiment sought to establish the vegetative indices for assessing tobacco float seedling varieties’ response to different fertilizer rates. A factorial design, with 3 variety × 4 fertilizer management treatments, was used. The N: P : K treatments were applied at 7, 21, and 35 days after sowing, while N treatments were applied at 42 days. Radiometric measurements were taken at 49, 56, 64, and 79 days after sowing on 8 tray plots, using a multispectral radiometer. Mature seedling samples were harvested at day 79 and stem lengths were determined before processing for total N analysis. All the five channels of the radiometer, the NDVI, and the SRI had a strong relationship with fertiliser rate. Both the NDVI and SRI for T66 were greater (P < 0.05) than those for KRK26 and KE1. The SRI had a stronger relationship with seedling dry mass, seedling count/tray, and stem length than the NDVI. The NDVI also showed a stronger relationship with total N than the SRI. The minimum threshold SRI and NDVI values and optimum growth (100% fertilser) were 0.72 and 6.1. This information is useful in identifying and estimating tobacco seedbed area and seedling vigour using remote sensing and, therefore, is important in forecasting potential tobacco crop area and yield

Development of tobacco (Nicotiana Tabaccum) yield estimation models using agronomic and remote sensing techniques

Farmers need to monitor crop growth and development and obtain early estimates of final yield. The unavailability of a comprehensive method for estimating crop yield leads to contradicting estimates, subjective national statistics and general planning inefficiency by stakeholders. In this study, experiments were conducted to select a suitable index for assessing varietal, planting date and fertilizer management influence on tobacco canopy reflectance. A hand-held multispectral radiometer was used to take canopy reflectance measurements. This was followed by an investigation into the relationship among canopy reflectance, in-season dry mass and final crop yield. The experiments were conducted at Kutsaga Research Station, near Harare in Zimbabwe. The MODIS satellite derived NDVI was used to assess tobacco growth, estimate crop area and final yield. The relationship between reflectance measurements from the multispectral radiometer and those from the MODIS satellite were used in up-scaling the multispectral radiometer derived yield estimation models for application on the sampled tobacco fields within a radius of 150 km from Harare. In this study, it is demonstrated that although simple ratio index (SRI) had a stronger relationship with biophysical parameters such as above-ground dry mass, plant population and plant height than NDVI, the latter was selected for use because of its stronger relationship with total nitrogen. Varieties, planting dates, and fertilizer application levels could be separated using spectral data between 9-12 weeks after planting. Thedifferent planting times could be separated from 0 to 9, 10 to 12,13 to 18 and 18 to 22 weeks after planting, thus demonstrating these as the optimum period for collecting spectral data for tobacco yield estimation. The mass at untying-NDVI regression coefficient of determination decreased with later planting from September (R2 = 0.79), October (R2 = 0.64), November (R2 = 0.695) and finally December (R2 = 0.515). The yield-NDVI regression models for the September and the October-planted crops were statistically similar (p = 0.424), and so were those for the November and December planted crops (p = 0.541). There were no significant differences (p = 0.220) among the mass at untying - NDVI regression curves for K RK 26, T 66 and K E1 and for the fertilizer application levels (p = 0.167). Since the relationships among tobacco in-season dry mass and yields with NDVI were not affected by tobacco variety and fertilizer application levels, a combined model for estimating tobacco yield using NDVI was developed. v Using remote sensing based on the MODIS satellite derived NDVI data, the third to fourth week of November and the third to fourth week of February were the optimal times for discriminating the September-October from the November-December planted tobacco. The tobacco crop areas for the 2010/ 2011, 2011/ 2012 and 2012/2013 cropping seasons were estimated, and yield estimates were calculated from the long-term cropped yield- area regression model. An up-scaling factor from the multispectral radiometer derived model to the MODIS derived model was developed, and a model for estimating tobacco yield using NDVI was derived. A regression analysis of the observed versus predicted yield was significant (p<0.05). The results show that tobacco yield can be estimated from the MODIS satellite derived NDVI using the model: Ytot = A(48.28 *av NDVIMOD2 – 37.51*av NDVIMOD+ 8.003). It is recommended that the model be used by tobacco industry to complement existing methods.,Tobacco Research Board (TRB