Historically, soil sampling has been a technique utilized for det

Historically, soil sampling has been a technique utilized for determining N rate recommendations. However, the reliability of soil N tests is often questionable due to the challenges associated with the dynamic nature of N in the soil, particularly selleck in the humid alluvial soils of Louisiana [4]. Therefore, crop yield monitoring has become an important aspect of many N management schemes. A common method of incorporating crop yield into N rate recommendations is through the use of yield goals, specifically in cereal crop production [5]. A yield goal is defined as yield per unit area we might expect to achieve given adequate growing conditions and it is determined by taking a recent five year average plus 30% to account for potentially above average growing conditions.
Johnson [6] and Schmitt [7] reported the importance of yield goal for N recommendations in winter wheat (Triticum aestivum) and corn (Zea mays), respectively. They indicated that 33 kg?N?ha?1 for every 1 Mg of wheat and 20 kg?N?ha?1 for every 1 Mg of corn would be required. However, setting yield goals at unrealistic levels can lead to under-or over-estimation of N rate recommendations. This is envisaged especially when N recommendations based on yield goals across large scale spatial variability do not take into account temporal variability, due to environmental growing conditions, nor within field spatial variability.Due to limitations associated with utilizing yield goals, research in other crops such as wheat and corn has focused on in-season crop monitoring as an approach to N management.
However, limited research is available for sugarcane production, particularly Louisiana sugarcane production. Additionally, research that is available has produced negative or inconclusive results [8,9]. Wiedenfeld [9] reported that chlorophyll meters were not a viable tool for predicting N recommendations for sugarcane grown in the Lower Rio Grande Valley. This lack of viability is partially due to the chlorophyll meter relying solely on plant tissue N concentrations and N accumulation in sugarcane occurred later in the season compared to when measurements were taken.Many plant indices based on canopy spectral reflectance have shown the ability to accurately estimate crop physiological properties, including plant biomass and crop yield [10�C12].
Brefeldin_A The NDVI value, which is a vegetative index that compares reflectance at the red and near infrared region, has also shown the ability to determine yield potential (YP) [13�C15]. Yield potential differs from yield goal because it is a function of the environmental conditions of the current growing season and is defined more info as achievable yield with no additional N fertilizer [11]. Teal [14] reported that there was a strong relationship between NDVI and grain yield in corn using an exponential model.

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