Control of Nutrient Mixing and Uptake by Irrigation Frequency and Relative Humidity
1991
Kargbo, D. | Skopp, J. | Knudsen, D.
The distribution of nutrients and water between mobile and immobile pores should influence nutrient uptake. The distribution can be regulated through control of the water-filled pore space. This research was conducted to determine the effect of varying soil-water content and water uptake upon nutrient uptake. Corn (Zea mays L.) was grown in a growth chamber for 2 wk at 35 or 55% relative humidity (RH). Three soils [Boelus LS, 5% slope (sandy over loamy, mixed, mesic Udic Haplustoll); Boelus LS, 2% slope; and Piano Soil (fine-silty, mixed, thermic Typic Haplustoll)] were watered to field capacity (θₘₐₓ). Plants on each soil were allowed to extract water to one of three minimal levels (θₘᵢₙ₁, θₘᵢₙ₂, θₘᵢₙ₃) before rewatering. After harvest, P and K content and other root and leaf parameters were determined. The values of θₘᵢₙ were chosen so that, for each soil, the three values ensured no low-water stress. Effective diffusion coefficients were determined for the three soils. Increased Omln for a soil required for frequent watering, which led to greater mixing of solutes between pores. At 55% RH, no water treatment significantly affected P and K flux, despite significant differences in diffusion coefficients. At 35% RH, however, phosphate flux to roots increased as θₘᵢₙ increased. The significant increase of phosphate flux with more frequent watering at low RH suggests that plant uptake is affected by soil physical processes other than simple diffusion and convection to individual roots. More frequent watering results in greater mixing of solute between pores containing mobile and immobile water and, consequently, greater uptake. Published as Paper Number 9594, Journal Series, Nebraska Agric. Exp. Stn.
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