Effects of Water Stress on Soil Plant Analytical Development (SPAD) Chlorophyll Meter Reading and its Relationship to Nitrogen Status and Grain Yield of Soybean under Different Soil Types

An experiment was conducted in a vinyl house at Gifu University, Japan, from June to November 2007 to elucidate the water stress effects on Soil Plant Analytical Development (SPAD) chlorophyll meter reading (SCMR) and its relationship to nitrogen status and grain yield of soybean under the three soil types. The first factor was the three soil types, comprising clay loam, sandy clay loam, and sandy loam, classified as Inceptisol, Ultisol, and Andisol, respectively. Water deficit (D) was the second factor with four levels including D_1(0-25%), D_2(25-50%), D_3(50-75%) and D_4(75-100%) of total available water (TAW). The soybean grain yield showed linear relationships with ET and LAI among the three soil types. On the other hand, soybean grain yield correlated with SCMR,…