Influence of Potassium Levels on Root Growth and Nutrient Uptake of Upland Rice Cultivars

Abstract

-Potassium (K) is an essential nutrient for upland rice growth, but little information on the effects of K on root growth and nutrient uptake capacity of upland rice is found. Therefore, an experiment was conducted under greenhouse conditions to evaluate the influence of soil K levels on root growth and nutrient uptake of four upland rice cultivars. A completely randomized experimental design, in a 4x4 factorial scheme (4 levels of K: 20, 40, 80, and 160 mg dm -3 ; 4 cultivars: Caiapó, BRS-Primavera, IAC-202, and Maravilha) was used, with four replications. Based on regression equations, the highest values of root length density would be found with 136 mg dm -3 of K. The root diameter and dry matter, shoot dry matter and shoot K concentration increased linearly with the increasing K rates. The shoot K concentration of the upland rice cultivars did not differ. The increased level of K in the soil reduced the shoot Ca concentration of intermediate and modern cultivars, and the shoot Mg concentration of all cultivars. The potassium fertilization increased the plant growth, but the magnitude of this effect varied according to the cultivar.

Effect of Irrigation Regimes and Soil Texture on the Potassium Utilization Efficiency of Rice

“…The high dry mass of the grains, leaves, and stems in the anaerobic-flooded regime was attributed to the sufficient amount of water and nutrients in the root zone for rice. By contrast, the low dry mass of the grains, leaves, and stems in the aerobic-flooded regime might be ascribed to soil cracks, providing an easy passage for water and nutrients to leak to the groundwater, and reducing the water and nutrients available to rice [56]. Previous research demonstrated that irrigation regimes could influence the growth and grain yield of rice [11,57].…”

“…In the present study, under the anaerobic-flooded conditions, big rooting systems were developed, transporting high amounts of K into the shoot parts. K application promoted the growth of the rice roots and the overall plant growth because of increasing contact between the ions and roots with increasing K availability in the soil [65], contributing to a high K uptake [56,66]. In plants, fundamental physiological processes, including photosynthesis and growth, are dramatically affected by K availability [67].…”

“…However, the physiological response of rice to nutrients in CF irrigation differs from that in AWD irrigation due to the decrease in nutrient availability in the latter [17,64]. In a previous study [56], in contrast to the control treatment, the greater response of the rice roots to K was attributed to the application of K, thereby promoting the availability of K in the soil. This phenomenon increased the K diffusion rate in the soil, and consequently, the contact between K and the rice roots.…”

“…This phenomenon increased the K diffusion rate in the soil, and consequently, the contact between K and the rice roots. Additionally, plants with big rooting systems can exploit great soil volumes and increase the contact between the roots and nutrients [56].…”

“…The greater value of KA was due to the higher K content and biomass in the anaerobic-flooded regime than in the aerobic-flooded regime. The high K concentration in the root zone could improve the crop yield [70] by increasing the K acquisition and the biomass production of rice [56,66]. The sharp decrease in KA in the aerobic-flooded regime was due to the disturbance in the overall plant growth and the low response to K was because reduction in the soil moisture content declines the K uptake in rice [71,72].…”