Potato (Solanum tuberosum) yield has been optimized for in‐row spacings ranging from 15 to 40 cm depending on region, targeted market, variety, and other factors. Production goals require optimizing tuber size to maximize crop value. Our goal was to evaluate the effect of plant, stem, and tuber density on stem and tuber set, potato yield, tuber size distribution, and other quality factors. Research plots were established within a 20‐ha commercial production field, and analysis was done with linear and nonlinear regression. Plant density decreased with increasing in‐row plant spacing. Stem density increased linearly with increasing plant density, but response differed across years. Tuber density increased to a maximum of 190 tubers m−2 in response to plant and stem density, with stem density more accurately predicting tuber set. Yield was related to plant, stem, and tuber density using nonlinear regression, more accurately predicted by stem and tuber density than by plant density. A hyperbolic model was used to predict yield with estimated maximum yield of 86 Mg ha−1 when related to stem density. Average tuber size was related to stem and tuber density using the inverse yield law and estimated maximum average tuber size of >200 g. The distribution for tuber sizes was estimated as a Weibull probability density function that predicted changes in tuber size in response to stem and tuber density. The hyperbolic model accurately predicted tuber density and yield with the added benefit that estimated parameters have biological importance, unlike polynomial or other regression models used to predict crop yield. Modeling tuber size distribution over different stem densities provides a mechanism for future economic analysis to optimize management and conduct sensitivity analysis to determine the most important factors influencing crop value.

A densely compacted soil layer has been a prevalent feature of the vegetable crop production region of Central Wisconsin, resulting in poor water drainage, increased susceptibility to tuber disease, and reduced yield and quality in potatoes. Subsoil tillage has been implemented on a widescale for management of problems associated with compacted soil layers. Pink eye is a tuber disorder that causes storage and processing losses. Periods of moisture stress and increased hill temperatures have been linked to pink eye incidence, but the cause of this disorder is unknown and few specific management recommendations exist. The goals of this work were to quantify the impact of compacted soils and subsoil tillage on development of potato pink eye. Small plot experiments were conducted to quantify response of soil conditions and potato pink eye to soil compaction and subsoil tillage. Compacted soils resulted in higher volumetric soil water content and extended periods of free water, especially after substantial precipitation events. Subsoil tillage allowed for more rapid movement of water following large precipitation events decreasing periods of free water. More compacted soils also had higher soil temperatures. Subsoil tillage delayed the development and progression of pink eye symptoms, but did not influence overall incidence. Increased soil moisture and temperature corresponded with more rapid development of pink eye in compacted and conventionally tilled soils. This research suggests subsoil tillage may be useful in reducing the severity of pink eye symptoms by alleviating compacted subsoil layers that limit water drainage. In addition, prevention of compaction reduced soil temperatures which limited pink eye development.Resumen Una capa de suelo densa y compacta ha sido la característica prevalente en la región de producción de hortalizas de Wisconsin Central, dando como resultado un drenaje deficiente, incremento de la susceptibilidad del tubérculo a las enfermedades y reducción del rendimiento y calidad de las papas. La labranza del subsuelo ha sido implementada en gran escala para el manejo de problemas asociados con capas de suelo compacto. El ojo rosado es un desorden del tubérculo que causa pérdidas durante el almacenaje y procesamiento. Los periodos de estrés de humedad e incremento de la temperatura del surco han sido relacionados con la incidencia de ojo rosado, pero se desconoce la causa de este desorden y existen pocas recomendaciones de manejo. Las metas de este trabajo fueron cuantificar el impacto de los suelos compactos y la labranza del subsuelo en el desarrollo del ojo rosado. Se realizaron experimentos en parcelas pequeñas para cuantificar la respuesta de las condiciones del suelo y ojo rosado de la papa, a la compactación del suelo y labranza del subsuelo. Los suelos compactos resultaron en contenido volumétrico de agua más alto y extensos periodos de agua libre especialmente después de una fuerte lluvia. La labranza del subsuelo permitió el movimiento más rápido del agua después de una lluvia fuer...

Compacted soils have been found in intensively cultivated vegetable crop regions of Central Wisconsin, resulting in the wide scale use of subsoil tillage by growers. Th e goal of this project was to assess potato (Solanum tuberosum L.) yield and quality response to soil compaction and subsoil tillage. Potato quality factors evaluated were marketable yield, tuber size distribution, internal quality, and sugar concentration. A controlled small plot experiment and several fi eld scale experiments located in collaborating grower fi elds were conducted to assess potato and soil responses to subsoil tillage. Cone index profi les showed the potential for limited root growth below the compacted soil layer with values >2.0 MPa. Subsoil tillage reduced cone index values to <1.0 MPa below 33 cm in 2 of 3 yr. Total and U.S. no. 1 yields were not infl uenced by subsoil tillage. Likewise, no consistent diff erences were seen in the size distributions of U.S. no. 1 tubers across treatments, but subsoil tillage tended to decrease proportion of tubers 113 to 170 g. Subsoil tillage did not aff ect tuber glucose or sucrose concentrations at harvest or following storage for 120 d. Internal tuber defects were not aff ected by either compaction or subsoil tillage. Th e lack of consistent eff ects of subsoil tillage on potato yield raises questions regarding the validity of this practice. Th e recommendation that potato growers use subsoil tillage may be linked to increased tuber size distribution or factors other than yield such as water, nutrient, or disease management.