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A PRECISE GRAVIMETRIC METHOD FOR SIMULATING DROUGHT STRESS IN POT EXPERIMENTS

Dep. of Crop and Soil Sciences, Univ. of Georgia, Athens, GA 30602-7272

View larger version (27K): [in a new window]   Fig. 1. Typical raw data from the lysimeter for a single replication of the soybean experiment. Each line represents a different pot, and is labeled with the final relative soil water content setting. Weight decreases were caused by transpiration of soil water, and increases were caused by automated additions of water whenever pot weights declined 30 g below the current target weight. Data collected during Period A were used to calculate whole plant water use under water-replete conditions. For each pot, a transpiration ratio was then calculated, as water use during Period B divided by water use during Period A.

View larger version (42K): [in a new window]   Fig. 2. Effect of target relative soil water content (RSWC) on horizontal distribution of soil water within the pots for the soybean (top) and cotton (bottom) experiments. Complete vertical soil cores were extracted from four different positions within each pot, and RSWC of each core was determined by weighing before and after drying. Each bar represents the mean of six (soybean) or seven (cotton) cores from different pots. Within an experiment and RSWC treatment, bars with the same letter do not differ (P > 0.05) according to a protected LSD test.

View larger version (24K): [in a new window]   Fig. 3. Effect of target relative soil water content (RSWC) on vertical distribution of soil water within the pots for the soybean (top) and cotton (bottom) experiments. Complete vertical soil cores were extracted from four positions in each pot (see Fig. 2), each core was divided into four equal sections, and RSWC of each section was determined by weighing before and after drying. Vertical axis shows approximate depth in pot of the middle of each section. Estimated soil core RSWC at each depth in each pot is the mean of RSWC estimates for the four core sections taken from that depth. Each data point represents the mean of estimates from six (soybean) or seven (cotton) different pots. Within an experiment and target RSWC, data points with the same letter do not differ (P > 0.05) according to a protected LSD test.