Cation‐exchange capacity (CEC) is an important soil property in describing nutrient availability for plant growth. Measurements of CEC, however, are often not available or have been measured using different analytical methods. The need, therefore, exists to develop alternative procedures to predict CEC from accessory soil properties. In this study, regression analysis was used to examine the relationships between CEC and clay (CLAY), organic carbon (OC), and other soil properties. Multiple regressions indicated that CLAY, OC, and soil pH accounted for up to 51% of the variation in CEC for all soil (n = 37921). For soil orders, CLAY and OC accounted for up to 67% of the variation in CEC for Alfisols, Inceptisols, Mollisols, and Vertisols, and up to 78% of the variation in CEC for Entisols and Spodosols. The OC alone accounted for up to 73% of the variation in CEC for Spodosols. Poor predictions of CEC resulted from CLAY for Aridisols and Vertisols, indicating that factors other than CLAY interfered with accurate predictions of CEC.
The quantification of radiation‐use efficiency (RUE), the amount of dry matter produced per unit of intercepted photosynthetically active radiation, is important for yield modeling and determination of yield potentials in different environments. This study was conducted to determine the mean RUE value of potato (Solanum tuberosum L.) and its stability across diverse environments. Radiation use efficiency was computed with growth analysis data from a field experiment with four cultivars conducted in Hawaii at four elevations, from field experimentation in Washington and Oregon, and from field experiments described in the literature for seven other locations. Radiation‐use efficiency values in Hawaii varied from 2.2 g MJ−1 at 91 m elevation to 2.8 g MJ−1 at 1097 m. Genotype means in Hawaii varied from 2.2 to 2.5 g MJ−1. Comparisons across locations indicated RUE was significantly related to mean daily temperature (r2 ‐ 0.34, n = 12, P < 0.05), vapor pressure deficit (VPD) (r2 = 0.63, n = 12, P < 0.01), and mean total solar radiation (TSR) (r2 = 0.74, n = 11, P < 0.01). Inclusion of either a VPD effect or a solar radiation effect in models of potato growth should improve dry weight predictions.
Mulching plays an important role in ameliorating soil and environmental stresses of most tropical crops. But for non-tropical crops such as potato, the beneficial effects are somewhat obscured by the incompatibility of mulching with existing soil and crop management practices. This paper reviews the main features of mulching. It basically describes the performance of selected mulch materials in potato systems, assesses their beneficial and/or adverse effects, and outlines potential avenues for developing efficient mulching techniques for potato.
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