Abstract
Penetration resistance, root length density, and water content of soil with maize (
Zea mays
L.), soybean (
Glycine max
L. Merr.), or a mixture of alfalfa (
Medicago sativa
L.) and fescue (
...Festuca arundinacea
Schreb.) were measured during two summers, one of which was dry. Plants grew on a silt loam (Mollic Albaqualfs; fine, mixed, thermic), 0.25 m deep overlying a claypan, 1.75 m thick. Half of the plots were subsoiled before planting in the first year of the study and the other half were not subsoiled. During both years, subsoiling had no measurable effect in lowering the penetration resistance in the claypan. Root length density was greater in the claypan than in the topsoil. Subsoiling did not increase root length density in either year. Water content in plots that had been subsoiled was usually similar to that in plots that had not been subsoiled. In the dry year, roots of maize proliferated more in the claypan than did roots of soybean or alfalfa + fescue.
Laboratory and greenhouse experiments were performed for 9 Kansas soil types to determine percentage sand, silt and clay, moisture content percentage by weight (θ m) at -1/3 bar and -15 bar water ...potential, and soil factors that quantity the soil's drying rate: U, the cumulative evaporation during the energy-limiting stage; and c, the least squares slope of evaporation rate versus $\text{time}^{1/2}$ during the soil-limiting stage of soil surface evaporation. Hydrometer method for mechanical analysis was used to determine the particle-size distribution, and pressure plate method was used to determine Θ m. U and c were obtained from weight losses from soil columns in a greenhouse experiment. Results of the experiment indicated that particle size composition and percentage water-holding capacity (WHC) influenced the values of U and c obtained. U and c were relatively low for sandy soil and soil with low WHC but higher for soil with greater WHC and percentage silt. The values of U ranged from 5 to 18.7 mm; of c, from 1.68 to 3.73 mm $\text{day}^{-1/2}$.
The short-term effects of intermittently applied low concentrations of SO2 (0.035 and 0.45 ppm) on net photosynthesis in field-grown wheat (Triticum aestivum L.), were studied at various growth ...stages. Photosynthesis was inhibited rapidly and remained at a reduced level as long as the 0.45 ppm SO2 was present. Photosynthesis was not inhibited at 0.035 ppm SO2. Inhibition was greatest during the vegetative growth stages. Though kinetics of water use during SO2 treatment generally followed that of photosynthesis, water use remained high, resulting in decreased water-use efficiency. Photosynthesis recovered fully shortly after each exposure, and final yield was not affected.
Use of spectral data to assess wheat response to soil water Kanemasu, E.T. (Kansas State Univ., Manhattan (USA). Evapotranspiration Lab.); Ransom, J; Saunders, D ...
Field Crops Research (Netherlands),
(1985), Volume:
12, Issue:
2
Publication
