Response of Sophora secundiflora to nitrogen form and rate
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Texas mountain laurel (Sophora secundiflora) is a native shrub tolerating drought, heat, windy conditions, and alkaline or wet soils. However, its availability is somewhat low and little information is available on nutrient requirement and other culture information. Two greenhouse experiments were conducted to quantify the responses of Texas mountain laurel to different forms and rates of nitrogen (N) fertilizer. In Expt. 1, 1-year old seedlings were treated for 194 days with three NO 3:NH 4 ratios at 25:75, 50:50, and 75:25 and two rates of N at 100 and 200 mgL -1 in a factorial design. There was no interaction between the N rate and form on any growth parameters. Nitrogen form did not significantly affect shoot dry weight, root dry weight, root-to-shoot ratio, or the total dry weight. There was no significant difference between N rate of 100 and 200 mgL -1 on root dry weight, root-to-shoot ratio, or the total dry weight. The shoot dry weight of Texas mountain laurel fertilized with 100 mgL -1 was higher compared with that of the plants fertilized at 200 mg.L -1. The reduced shoot dry weight at N of 200 mgL -1 was the result of the higher infstrate salinity. In Expt. 2, seedlings were fertilized with five N rates (50, 100, 150, 200, and 250 mgL -1) for 203 days. Plants watered with 150, 200, and 250 mgL -1 were taller than those fertilized with 50 mgL -1. The shoot height of plants watered with 100 mgL -1 was only significantly different from 50 mgL -1. For rapid growth of Texas mountain laurel, a N rate range of 150 mgL -1 was recommended supplied with a combination of NO 3-N and NH 4-N in the ratios of 0.3 to 3.0.
