2002-07-08_GENERAL DOCUMENTS - M2002004 (4)

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Table 2- Yields of wheat and intermediate wheatgrass grown on five topsoil thickness treatments, and yield of intermediate wheatgrass as affected by N fertilizer on four topsoil thickness treatments in the greenhouse. Topsoil Yield component thickness Total herbaget IISDI Roots in topsoil HSD Roots in spoil HSD Biomass (herbage and roots) HSD cm t Total of two harvests. $ Tukey's Honestly Significant Difference. Intermediate wheatgrass Not Wheat fertilized Fertilized g /pot 0 2.50 1.47 3.99 10 5.72 4.18 11.19 20 10 03 7.51 14.07 30 14.56 11.78 17.92 46 22.17 16.65 - 1.59 1.77 2.77 0 - - -- 10 2.22 2.88 6.30 20 3.36 6.34 9.32 30 4.01 10.52 13.19 46 8.92 13.24 - 2.50 2.17 1.98 0 1.11 2.72 8.01 10 0.93 3.58 6.89 20 0.87 3.93 6.95 30 0.93 4.28 5.32 46 0.98 4.12 - NS NS NS 0 3.61 4.19 12.00 10 8.87 11.04 24.38 20 14.26 17.78 30.34 30 19.50 26.58 36.43 46 32.07 34.01 -- 2.97 4.17 7.77 ness of topsoil in a field study. When averaged across all topsoil thickness treatments, total herbage production per can was 32% higher for wheat than for intermediate wheatgrass (Table 2). Wheat averaged 2.20 and 8.80 g /can and intermediate wheatgrass averaged 2.58 and 5.74 g /can for the first and second harvests, respective- ly. The fertilizer treatment increased total herbage pro- duction of intermediate wheatgrass an average of 89% over the same nonfertilized treatments. Root production of both species was much greater in Fig. la -Root and herbage production (second harvest) of wheat on five topsoil thickness treatments, increasing from 0 cm on left to 46 cm on right. Arrows mark depth of topsoil. Table 3- Herbage and root yields for intermediate wheatgrass and wheat grown on a mixture of topsoil and spoil material compared with yields on equivalent thickness of topsoil in the greenhouse. Yield component Topsoil type Total herbaget mix$ 6.16 "15 cm" 5.84 Roots in topsoil mix 5.80* "15 cm" 4.61 Roots in spoil mix 2.61§ "15 cm" 3.95 Biomass (herbage + roots) mix 14.57 "15 cm" 14.41 Intermediate wheatgrass Wheat g/can 8.30 7.87 2.99 2.79 0.55 0.90 11.84 11.57 t Total of two harvests. $ Mix = 30 cm of equal volume mixture of topsoil and spoil material on top of 23 cm of spoil. "15 cm" = average of values for 10 and 20 cm of topsoil on top of spoil. § Means in pairs of "roots in topsoil" and "roots in spoil" differ sig- nificantly (5%); no significant difference between means in other pairs. topsoil than in spoil material and increased linearly with thickness of topsoil (r = 0.89). Intermediate wheatgrass roots averaged 0.31 g /cm of topsoil thickness and 0.15 g /cm of spoil, but wheat root growth averaged only 0.17 g /cm of topsoil thickness and 0.04 g /cm of spoil. For all depths of topsoil, intermediate wheatgrass sent more roots down into the spoil than did the wheat (Fig. 1). The low root production by both species when grown in spoils alone and in the spoil beneath the topsoil is at- tributed to the low levels of P and available N in the spoil. Reeder and Berg (1977) reported that only a por- tion of the total N in these spoil materials is available for plant uptake. Both species produced more fine roots in the topsoil than in the spoil material. When root weights in topsoil and the underlying spoil were com- bined, average root production per can was 10.40 g for intermediate wheatgrass and 4.67 g for wheat. The N- fertilizer treatment increased root production of inter- mediate wheatgrass an average of 46% in the topsoil and an average of 87% in the spoil (Table 2). Although N fertilizer increased root production in the spoil, these Fig. lb -Root and herbage production (second harvest) of intermedi- ate wheatgrass on five topsoil thickness treatments, increasing from 0 cm on left to 46 cm on right. Arrows mark depth of topsoil. J. Environ. Qual., Vol. 9, no. 4, 1980 683