Jason W. Ellsworth

Canopy Reflectance Estimation of Wheat Nitrogen Content for Grain Protein Management

The objective of this study is to evaluate remote sensing as a tool for measuring wheat nitrogen (N) content and then demonstrate how that information may be used by crop managers to improve grain protein content. Remote sensing data from aerial and satellite platforms were collected and compared with flag leaf N concentrations. Flag leaf N was significantly correlated with reflectance (r 2 = 0.52-0.80) during 2002 and 2003. A mid-season application of N increased grain protein in every treatment, but most significantly in the N-stressed treatments. Using remote sensing as a tool, wheat growers can estimate N stress and make decisions about protein management.

Evaluation of potato production best management practices

A 2001 survey indicated that many growers are reluctant to adopt research-based recommendations because of a perception that it is not practical or applicable to their specific farming operation. Other growers, however, appear to adopt these practices successfully. Highlighting “model” growers is a method that can be used to field-test research findings and facilitate grower adoption. The objectives of this project were to: 1) establish field demonstrations with potato (Solariumtuberosum L.) growers who generally follow researchbased best management practices (BMPs); 2) establish plots within each field to compare BMPs with a high input, maximum yield management (MYM) approach; and 3) enhance grower confidence regarding researchbased BMPs. Fourteen field trials were conducted in the Pacific Northwest during 2002-2005. Five replicates of BMP and MYM plots were established in each field. The BMPs consisted of sampling, scouting, and use of prediction models to aid in determining rate and timing of inputs to maximize returns. In contrast, the MYM approach was based on tradition and calendar timing, with a near zero tolerance for pest and nutrient limitations. The MYM plots had 1.7 to 13.2% more fertilizer and pesticide costs than the BMP plots. The MYM treatments resulted in significant marketable yield increases in three fields and decreases in two fields, with the remaining nine fields and the combined average of all 14 fields being statistically equivalent. When factoring in estimated costs, only two fields resulted in a monetary advantage with MYM treatment. In contrast, the BMP treatment resulted in significant increases in net crop value in five fields, as well as the combined average of all 14 fields (

PHOSPHORUS FERTILIZER TIMING FOR RUSSET BURBANK POTATO GROWN IN CALCAREOUS SOIL

200 ha-1 or 3.2%). These field demonstrations, along with associated field days and grower meetings, have resulted in many documented changes in grower practices towards BMPs, with many more undocumented changes probable.ResumenUn estudio que se hizo el 2001 indica que muchos agricultores son renuentes a adoptar las recomendaciones basadas en la investigación, debido a una percepción poco práctica o aplicable a sus operaciones de cultivo. Otros, sin embargo, parecen adoptar exitosamente estas prácticas. El destacar a los agricultores “modelo” es un método que pude ser usado para probar en el campo los resultados de la investigación y facilitar su adopción. Los objetivos de este proyecto fueron: 1) hacer demostraciones de campo con los agricultores que cultivan papa (Solarium tuberosum L.) que emplean generalmente las mejores prácticas de mane jo (BMPs) basadas en investigación; 2) establecimiento de parcelas dentro de cada campo las BMPs con gastos altos, un enfoque de manejo máximo de rendimiento (MYM); 3) incremento de la confianza del agricultor referida a los BMPs basados en investigación. Catorce pruebas de campo se realizaron el Pacñfico Nor Occidental durante 2002-2005. Cinco repeticiones de BMP y de MYM se hicieron por parcela en cada campo. Los BMPs consistieron de muestreos, exploración y uso de modelos de predicción para ayudar a determinar la tasa y registro de gastos para alcanzar el máximo de ganancia. Contrariamente, el enfoque MYM estuvo basado en la tradición y distributión del tiempo, con tolerancia cero para problemas de pestes y nutrientes. Las parcelas MYM recibieron 1.7 a 13.2% de gastos en fertilizantes y pesticidas que las parcelas BMP. Los tratamientos resultaron en aumento significativo de rendimiento comerciable en tres campos disminución con los restantes nueve y el promedio combinado de los 14 campos estadñsticamente equivalentes. Cuando se factorizó en gastos estimados, sólo dos campos resultaron en ventaja monetaria con el tratamiento MYM. Contrariamente, el tratamiento BMP dio como resultado un incremento significativo en cinco campos, asñ como el promedio combinado de todos los 14 campos (

PRE-PLANT VERSUS IN-SEASON APPLICATION OF PHOSPHORUS FERTILIZER FOR RUSSET BURBANK POTATO GROWN IN CALCAREOUS SOIL

200 ha-1 o 3.2%). Estas demostraciones de campo, junto con los asociados dñas de campo y reuniones de agricultores, han dado como resultado muchos cambios documentados en el proceder de los agricultores hacia los BMPs, con cambios probables no documentados.

MONOPOTASSIUM PHOSPHATE AS AN IN-SEASON FERTIGATION OPTION FOR POTATO

Potato (Solanum tuberosum L.) has surface roots with enhanced activity upon canopy closure that should allow application of phosphorus (P) via fertigation. Fertilizer trials were conducted in 2005–2006 with four pre-plant broadcast (0, 112, 224, or 336 kg P2O5 ha−1) and two split applied in-season fertigation (0 or 56 kg P2O5 ha−1) rates. Total and undersized tuber yield had a quadratic relationship with pre-plant P, increasing and then declining as pre-plant P fertilizer rate increased, with predicted yield peaks at 246 and 167 kg P2O5 ha−1, respectively. Marketable and US No. 1 yields increased linearly with increasing pre-plant P fertilizer rate. A trend for an increase in total yield as a function of in-season P fertilization was also measured. The P rate for maximum yield did not decline with in-season application, suggesting that this practice does not enhance P fertilizer use efficiency.

Nitrogen deficiency and recovery in sustainable corn production as revealed by leaf chlorophyll measurements

Potato (Solanum tuberosum L.) has active surface roots that may enable phosphorus (P) fertigation. Fertilizer trials were conducted in 2002–2004 with 0 or 224 kg P2O5 ha−1 applied as incorporated pre-plant broadcast, in-season fertigation, or split application (half pre-plant and half in-season). All of the P fertilization treatments increased petiole P concentration over the untreated control in all three years of the trial, but only the pre-plant application resulted in significant increases in US No. 1 and Total yields. Both the pre-plant and the split application resulted in significant increases in Marketable yield (US No. 1 & 2). These results show that P fertilizer should be applied and incorporated prior to planting. Fertigated P does enter into the plant, but the relative efficiency of this method of application for P is poor with regard to important yield and quality parameters and application as such should be limited to “rescue” situations.

Soil pH effects on nitrification of fall-applied anhydrous ammonia

Monopotassium phosphate (MKP) is a potential option for fertigating phosphorus (P) in potato (Solanum tuberosum L.) when petioles are low in P and high in nitrogen (N); which is a situation where using ammonium polyphosphate (APP) could potentially result in excessive N application. Fertilizer trials were conducted in 2004–2006 with 0 or 56 kg P2O5 ha−1 fertigated as either APP or MKP as a supplement to the pre-plant P (112 or 224 kg P2O5 ha−1) broadcast applied to all plots. Supplemental P fertigation increased petiole P concentration, US No. 1 yield, and total yield over the control not receiving any in-season P fertilizer regardless of source. In addition, MKP increased tuber specific gravity. These results support previous studies showing that fertigated P can be used to increase potato yields when petiole P concentrations are low and that MKP is a viable substitute for APP fertilizer when fertigation is necessary.

Iron Nutrition in Field Crops

Assessing economic and environmental impacts of nitrogen (N) fertilization in production agriculture is important for preventing unnecessary application of N fertilizer and avoiding losses of this N into water body. Chlorophyll meters are often used to evaluate N management practices and diagnose deficiencies of N in corn (Zea mays L.). Chlorophyll meter readings (CMRs) are usually interpreted relative to reference readings taken from plants having ample N to maximize rates of growth. Although measurements taken with chlorophyll meters provide a scale for estimating the sufficiency of N for corn growth, effects of above-optimal supplies of N on the measurements have not been studied when diagnosing N deficiencies during vegetative growth stages. Here, temporal trends in chlorophyll measurements were monitored in trials where various rates of N were applied soon after planting and (or) after symptoms of N deficiency had developed due to the changes of N status in soil and demand for N during corn growth. Divergence of chlorophyll measurements from the reference readings occurred in situations where plants having too little N were compared with plants having adequate N. In contrast, convergence of chlorophyll measurements with the reference readings after application of fertilizer N during the growing season indicated partial or complete recovery of the plants from the deficiency of N. The recovery can be explained by considering that luxury production of chlorophyll occurred at higher rates of fertilization or by interactions of N with soil water and other nutrients supplied during corn growth. Observations that plants can partially or completely recover from periods with inadequate N for chlorophyll production suggest that the leaf chlorophyll measurements taken early in the season should not be always expected to highly correlate with final yields of grain. Therefore, it is important to recognize the possible recovery of chlorophyll production and to avoid N losses to the environment.