Chad M. Hutchinson

Effect of cover crop and management system on weed populations in lettuce

Abstract Changes in cropping systems can significantly impact pest population dynamics and management. Field experiments were conducted from 1998 to 2000 to study the effect of summer cover crop and in-season management system on weed infestations in lettuce ( Lactuca sativa L.). The experiment was a factorial with summer cover crop and management system as the two factors. Cover crops were cowpea [ Vigna unguiculata (L.) Walp.] incorporated into the soil in the fall (CWPI), cowpea used as mulch in the fall (CWPM), sudangrass ( Sorghum vulgare ) incorporated into the soil in the fall (SDNG), and dry fallow (DFLW). Management systems were organic (ORG), integrated crop management (ICM), and conventional (CNV). In general, there was no interaction between cover crop and management system. Weed species richness was greatest early in the growing season and was affected by cover crop. Fewer species emerged in CWPM plots in general but perennial species became important with time. The DFLW showed greater weed populations than all cover crop treatments. Weed populations were similar in all management systems in 1999. However, in 2000, there was better weed suppression in the ORG and ICM systems than in the CNV system. CWPI significantly increased lettuce yield and DFLW yield declined the second year. Yield under the ORG system was low in 1999 and equivalent to that in the CNV and ICM systems in 2000. These results indicate that a prior summer cover crops can improve both conventional and organic vegetable production systems.

Environmentally Responsible Potato Production Systems: A Review

ABSTRACT More than 500,000 hectares of land is planted to potato crop each year in the United States. Intensive nutrient-management practices for potato cultivation have led to increased concerns about nitrate leaching in these soils. Studies on nitrogen (N) uptake characteristics of potato roots have shown that N fertilizers are applied in excess of the optimal rate for maximum yield. This paper discusses all current and relevant research on nutrient and water management issues that have lead to improved nitrogen use efficiency for successful potato production and minimized groundwater impacts. Specific topics within the nutrient-management section include mineral fertilizers, nutritional requirements, N uptake and the root system, slow and controlled-release fertilizers, organic sources of nutrients, and nitrification inhibitors. Research on alternate methods of irrigation currently in use and available for potato production is discussed. Application of prediction models to optimize all the components for sustaining both economical and environmental goals is also discussed, with an emphasis on the immediate need for linking nutrient management traditionally aimed at crop yields with the preservation of water quality in all future research programs.

Evaluation of Controlled-Release Fertilizers for Northeast Florida Chip Potato Production

ABSTRACT Controlled-release fertilizers (CRF) were compared with ammonium nitrate (AN) in a potato (Solanum tuberosum L.) production study at the University of Florida farm in Hastings, FL, in 2002. Treatments were no nitrogen (No-N), AN, and nine CRFs at 146 kg ha−1 N and 225 kg ha−1 N. CRF7 (146 kg ha−1 N) resulted in highest total and marketable yields at 33.7 MT ha−1 and 29.4 MT ha−1, respectively. Tubers from the AN (225 kg ha−1 N) and CRF9 (225 kg ha−1 N) treatments had the highest specific gravity at 1.073. Nitrogen removal efficiency was highest in plants in CRF1 (43.0%) and CRF7 (47.3%) plots. Both were significantly higher than AN-treated plants. At 39 days after planting, NO3-N and NH4-N concentrations in lysimeter water samples were significantly higher in AN treatments. Leaf tissue N concentrations were sufficient throughout the growing season in all treatments except No-N.

Testing of Controlled Release Fertilizer Programs for Seep Irrigated Irish Potato Production

Abstract A Best Management Practices (BMP) program has been implemented for Northeast Florida potato (Solanum tuberosum) producers to reduce the potential for nitrate (NO3) leaching from the 9000 ha of land in potato production in the St. Johns River watershed. Controlled release fertilizers (CRFs) could supply nutrients to potatoes while reducing the potential for off‐site movement of nutrients thus, providing a long‐term solution to the problem of NO3 leaching on sandy soils. The objectives of this project were to evaluate the quality and quantity of potatoes fertilized with CRFs and soluble fertilizers and to determine the influence of nitrogen (N) source on N use efficiency (NUE). Fertilizer treatments were: (a) no N control; (b) ammonium nitrate (AN) and urea; (c) polymer coated urea (PCU) and polymer sulfur coated urea (PSCU); (d) polymer coated 11‐11‐11 product; and (e) polymer coated 15‐9‐12 product. Fertilizers treatments were each applied 112, 168, and 224 kg ha−1. The highest total and marketable yields were obtained with CRF 15‐9‐12 (224 kg N ha−1), PCU + PSCU (168 kg N ha−1), and AN + Urea (224 kg N ha−1) averaging 44.2 and 39.9 MT ha−1 respectively, across the three treatments. Total and marketable yield for the no N treatment were 11.2 and 9.3 MT ha−1, respectively. All leaf N levels were within the sufficient range except for plants in the no N, AN + urea (112 kg N ha−1), PCU + PSCU (112 kg N ha−1), and CRF 11‐11‐11 (112 and 168 kg N ha−1). Nitrogen removal by plant tissue ranged from a high of 94.3 kg N ha−1 to a low of 10.7 kg N ha−1 for the 15‐9‐12 (224 kg ha−1) and no N treatments, respectively. At low N rates, CRFs had higher NUE than the soluble fertilizers. Nitrogen use efficiency was similar among all fertilizer sources at higher N rates. #This research was supported by the Florida Agricultural Experiment Station and approved for publication as journal series no. R‐09126.

Efficacy of methyl iodide and synergy with chloropicrin for control of fungi

Efficacy of soil fumigation with methyl bromide and methyl iodide against Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium oxysporum, Gliocladium virens, Phytophthora citricola, Phytophthora citrophthora, Pythium ultimum, Rhizoctonia solani and Verticillium dahliae was determined in laboratory experiments in closed fumigation chambers. Pythium ultimum was the most sensitive fungal species with EC 50 values for methyl bromide and methyl iodide of 15.5 and 8.6 μM, respectively. R solani was the least sensitive with EC 50 values of 253.4 and 161.4 μM for methyl bromide and methyl iodide, respectively. Relative potency ([methyl bromide]/[methyl iodide]) values ranged from 5.2 for P citricola to 1.5 for F oxysporum. Methyl iodide was 2.7 more efficacious than methyl bromide averaged over all fungal species. Methyl bromide/chloropicrin and methyl iodidelchloropicrin applied jointly were 2.2 and 2.8 times more efficacious, respectively, against F oxysporum than when the compounds were applied singly. Combining methyl bromide and methyl iodide with chloropicrin resulted in a significant synergistic increase in activity against F oxysporum.

Root distribution under seepage-irrigated potatoes in Northeast Florida

Much of commercial potato production in Florida is irrigated using sub-surface seepage irrigation. A perched water table is maintained during the season within 50 cm below the top of the potato ridge. Fertilizer placement is critical in this system to maximize plant uptake and to minimize leaching potential. Optimal placement of fertilizers is dependent on root distribution. The objectives of this study were to develop and test a new methodology to spatially describe potato root distribution as affected by nitrogen rate and irrigation system. Soil slices containing representative samples of the potato root system at full flowering were taken from plots fertilized with ammonium nitrate at 168, 224, and 280 kg N ha−1. The proposed sampling methodology performed satisfactorily. Root length density (cm root cm−3 soil) and specific root length (cm root mg−1 root dry weight) were not affected by nitrogen rate, but were affected by spatial position in the soil profile. The highest root length density value (0.72 average) was observed within 12 to 15 cm of the seedpiece. Low root length density values averaging 0.036 were observed between 24 and 36 cm from the top of the ridge. Specific root length values indicated a relatively homogeneous root system in terms of the quantity of invested biomass by unit of root length except in the two central units below 24 cm from the top of the ridge where thickened roots caused significant lower values averaging 6.47 as compared with the average of 15.87 from the surrounding Units in the slice. Root thickening in deep apical roots suggested aerenchyma formation promoted by a combination of saturated soil conditions in the root zone caused by inappropriate irrigation management and soil compaction. Fertilizer placement under the seedpiece should be a good alternative to increase potato nitrogen uptake under seepage irrigation.ResumenLa producción comercial de papa en la Florida es irrigada por percolación sub-superficial. Durante la temporada de producción el nivel freático se mantiene a 50 cm por debajo de la cima del caballón donde la papa ha sido sembrada. La localización del fertilizante es un punto crítico en este sistema para maximizar la absorción y minimizar el potencial de lixiviación. La localización óptima del fertilizante depende de la distribución de las raices. Los objetivos de este estudio fueron desarrollar y validar una nueva metodología para describir espacialmente la distribución de las raices de la papa bajo efecto de la dosis de nitrógeno y el sistema de irrigación. En plena floración de la papa fueron muestreados perfiles de suelo conteniendo muestras representativas del sistema radicular de parcelas fertilizadas con nitrato de amonio en dosis de 168, 224, y 280 kg N ha−1. La metodología propuesta funcionó satisfactoriamente. La densidad de longitud de raíces (cm raiz cm−3 suelo) y la longitud radicular específica (cm raiz mg−1 peso seco de raiz) no fueron afectadas por la dosis de nitrógeno pero si por su posición espacial en el perfil del suelo. Los valores mas altos de densidad de longitud de raíces (0.72 en promedio) fueron observados en una zona de 12 a 15 cm circundando la semilla. Entre 24 y 36 cm de profundidad fueron observados valores bajos de densidad de longitud de raíces con 0.036 en promedio. Los valores de longitud radicular específica indicaron un sistema radicular relativamente homogéneo en términos de la cantidad de biomasa invertida por unidad de longitud radicular excepto en los dos ambientes centrales por debajo de 24 cm de profundidad donde raíces engrosadas causaron bajos valores significativos promediando 6.47 comparados con el valor promedio de 15.87 observado en el resto de los ambientes estudiados. El engrosamiento apical en raíces profundas sugieren la formación de aerénquima promovido por la combinación de saturación del suelo en la zona radicular causada por manejo inapropiado de la irrigación, y compactación del suelo. La colocación del fertilizante debajo de la semilla de la papa podría ser una buena alternativa para incrementar la absorción de nitrógeno en condiciones de irrigación por percolación.

Potato (solarium tuberosum l.) yield and internal heat necrosis incidence under controlled-release and soluble nitrogen sources and leaching irrigation events

Best management practices (BMPs) have been developed for northeast Florida potato production with the objective of reducing N fertilizer use while main-taining tuber yield and quality. However, rainfall timing and intensity can affect soil N availability, tuber yield, and quality. Objectives of this study were to determine the influence of fertilizer source (soluble and controlled-release) and timing of leaching irrigation on tuber yield and quality of ‘Atlantic’ potato in a seepage-irrigated production system. The experiment was conducted in 2004 and 2005 as a split-split plot with four replications. Main effects were leaching irrigation treatments (no-leaching irrigation and leaching irrigation at 2, 4, 8 and 12 weeks after planting [WAP]), N source (ammonium nitrate [AN] at 224 kg ha-1 or controlled-release fertilizer [CRF] at 196 kg ha-1), and supplemental N sidedress application (34 kg N ha-1). In 2004, total and marketable tuber yields for plants in the 8 and 12 WAP leaching treatments were 10% and 11% lower, respectively, than plants in the no-leaching treatment. In 2005, marketable tuber yields from plants in the no-leaching treatment were significantly higher than plants in the 4, 8 and 12 WAP leaching treatments. Plants in CRF treatments produced significantly higher marketable tuber yields in both years compared with plants in AN fertilizer treatments. Supplemental N sidedressing did not improve tuber yield or quality in either year. Plants in the CRF treatment had a higher incidence of tubers with internal heat necrosis (IHN) in 2004 and 2005 compared with plants in the AN fertilizer treat-ment. This suggests that under severe leaching pres-sures, CRF needs a faster soil nutrient “recharge” to reduce plant nutrient stress. Plants in the CRF treatment averaged 12% higher marketable tuber yields with 13% less N applied compared with the AN treatment. Overall, CRFs are well suited as a BMP for northeast Florida potato production.ResumenPara la producción de papa en el noreste de Florida se han desarrollado unas mejores prácticas de mane jo (BMPs) con el objeto de reducir el uso de la fertilización con N mientras se mantiene el rendimiento y la calidad del tubérculo. Sin embargo, el momento e intensidad de lluvias pueden afectar la disponibilidad de N en el suelo, la calidad y rendimiento de tubérculos. Los objetivos del presente estudio fueron determinar la influencia de la fuente del fertilizante (soluble y de liberación controlada) y momento de irrigación por lixiviación sobre el rendimiento y calidad del tubérculo de papa ‘Atlantic’ con el sistema de producción subirrigado. El experimento se realizó en 2004 y 2005 como parcela subdividida con cuatro repeticiones. Los efectos principales fueron los tratamientos de irrigación por lixiviación (irrigación sin y con lixiviación a las 2, 4, 8 y 12 semanas después de la siembra [WAP]), fuente de N (nitrato de amonio [AN] a 224 kg ha--1 o liberatión controlada de fertilizante [CRF] a 196 kg ha-1) y aplicación suplementaria en bandas de N (34 kg N ha-1). En 2004, el rendimiento total y comercial de tubérculos en los tratamientos de lixiviación de 8 y WAP fueron 10% y 11% más bajos, respectivamente que en plantas en el tratamiento sin lixiviación. En 2005, el rendimiento de tubérculos comerciables de plantas en el tratamiento sin lixiviación fueron significativamente más altos que en plantas en los tratamientos con lixiviación de 4, 8 y 12 WAP. Las plantas en los tratamientos CRF dieron rendimientos más altos de tubérculos en ambos años en comparación con plantas de los tratamientos con fertilizante AN. El tratamiento con N suplementario en bandas no mejoró el rendimiento o la calidad de los tubérculos en ambos años. Las plantas en el tratamiento CRF tuvieron una alta incidencia de necrosis interna (IHN) en 2004 y 2005 en comparación con plantas en el tratamiento del fertilizante AN. Esto sugiere que bajo severa presión de lixiviación, el CRF necesita una “recarga” más rápida de nutrientes para reducir el estrés de la planta por nutrientes. Las plantas en el tratamiento CRF dieron un 12% más de tubérculos comerciables con 13% menos de N aplicado en comparación con el tratamiento AN. Los tratamientos CRF convienen más como un BMP para la productión de papa en el noreste de Florida.

Nitrate-nitrogen concentrations in the perched ground water under seepage-irrigated potato cropping systems.

Excessive nitrogen rates for potato production in northeast Florida have been declared as a potential source of nitrate pollution in the St. Johns River watershed. This 3-yr study examined the effect of N rates (0, 168, and 280 kg ha(-1)) split between planting and 40 d after planting on the NO(3)-N concentration in the perched ground water under potato (Solanum tuberosum cv. Atlantic) in rotation with sorghum sudan grass hybrid (Sorghum vulgare x Sorghum vulgare var. sudanese, cv. SX17), cowpea (Vigna unguiculata cv. Iron Clay), and greenbean (Phaseolus vulgare cv. Espada). Soil solution from the root zone and water from the perched ground water under potato were sampled periodically using lysimeters and wells, respectively. Fertilization at planting increased the NO(3)-N concentration in the perched ground water, but no effect of the legumes in rotation with potatoes on nitrate leaching was detected. Fertilization of green bean increased NO(3)-N concentration in the perched ground water under potato planted in the following season. The NO(3)-N concentration in the soil solution within the potato root zone followed a similar pattern to that of the perched ground water but with higher initial values. The NO(3)-N concentration in the perched ground water was proportional to the rainfall magnitude after potato planting. A significant increase in NO(3)-N concentration in the perched ground water under cowpea planted in summer after potato was detected for the side-dressing of 168 kg ha(-1) N applied to potato 40 d after planting but not at the 56 kg ha(-1) N side-dress. Elevation in NO(3)-N concentration in the perched ground water under sorghum was not significant, supporting its use as an effective N catch crop.