Relationship Between Coefficient of Variation Measured by Spectral Reflectance and Plant Density at Early Growth Stages

Nitrogen use efficiency (NUE) is estimated to be 33% throughout the world, current precision nitrogen application through precision sensing methods can improve NUE to a level of 50%. Statistical analysis of sensor data has not yet been evaluated for using in improving the prediction of potential yield. This study was conducted to evaluate the effect of plant population on the CV of early season NDVI values. Also evaluated in this study was the effect of seed row direction in relation to sensing direction on NDVI values. In 2003-2004 the relationship between the CV of NDVI values and plant population was determined. From this relationship a critical CV value was determined to be 20. Also observed was the trend that CV follows over time. This tend was shown to hold true across nitrogen treatments. Sensing direction was shown to have no effect upon NDVI readings across seven site-years with multiple varieties, seeding rates, nitrogen rates and growth stages.Department of Plant and Soil Science

Analysis of the coefficient of variation of remote sensor readings in winter wheat, and development of a sensor based mid-season n recommendation for cotton

Scope and Method of Study: For chapter one, Hard red winter wheat (Triticum aestivum L.) experiments were conducted to better understand how the coefficient of variation (CV) could be used to better mid-season N rate recommendations. The CV's were calculated from the normalized difference vegetation index (NDVI) collected from each plot with a GreenSeeker Hand Held optical reflectance sensor. For chapter two, Cotton (Gossypium hirsutum L.) experiments were conducted to evaluate if spectral reflectance measurements could predict yield mid-season and be used to determine a mid-season N rate recommendation.Findings and Conclusions: For chapter one, CV was found to be a good predictor of plant population and when used as a component of mid-season response index calculation improved the relationship with the response index measured at harvest in terms of yield. A relationship between yield and CV was also observed. This work indicated that a previously proposed RINDVI-CV equation did not improve the prediction of the RI at harvest. For chapter two, over sites and years lint yield was predicted using the division of NDVI and Cumulative Growing Degree Day (CummGDD) units that accumulated from planting to sensing, the prediction was best when data was collected between 800 and 1300 CummGDD. The yield prediction model combined with the establishment of the relationship between the response index at harvest and mid-season; a nitrogen fertilization optimization algorithm was developed

Diagnosing nutrient deficiencies in canola

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Impact of sensor-based nitrogen management on yield and soil quality

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Cotton yield goal � Nitrogen rate recommendation

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Using the GreenSeeker handheld sensor and Sensor-Based Nitrogen Rate Calculator

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Understanding soybean nodulation and inoculation

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Dove field management

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

How does soil pH impact herbicides?

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Evaluating the Impact of Starter Fertilizer on Winter Canola Grown in Oklahoma

Increased canola production costs and acres have driven Oklahoma (OK) farmers to ask more questions about their nutrient management recommendations in their production system. A study was conducted in 2011–2013 at Lahoma and Perkins, OK, to evaluate the effect of applying diammonium phosphate (DAP, 18-20-0:N-P-K) directly with seed on crop stand, grain yield, and grain quality of canola. In addition, the impact of proportion nitrogen (N) applied as a preplant and topdress was also evaluated. Diammonium phosphate was banded with the seed at planting at 0, 17, 34, 51, 67, and 84 kg DAP ha−1. Remaining N was applied as urea (46-0-0) either as split (40% preplant and 60% topdress) application or as topdress only. Stand count reduction of up to 71% was observed with seed-placed DAP. However, loss of stand did not impair grain yield due to canola’s ability to compensate for open areas via branching. Application of DAP of up to 84 kg ha−1 with seed may be possible; however, soil and climatic conditions should be considered when deciding how much DAP will be placed with seed. Moreover, when climatic conditions limit early season growth and favor late spring growth, applying all N at topdress (no preplant) tended to provide greater canola grain yield