Gypsum and Compost Effects on Sugarcane Root Growth, Yield, and Plant Nutrients

are enhanced. Sugarcane germination can also be promoted by increasing soil Ca (Mohandas et al., 1983). Louisiana sugarcane (Saccharum spp.) is produced mainly on For some crops, gypsum is effective in reducing the heavy-textured soils that offer less than ideal conditions for growth and function of the root system. Cultural practices that improve the incidence of soil-borne diseases (Kao and Ko, 1986). soil environment could benefit sugarcane production by increasing Moreover, mixing 11.2 and 22.4 Mg ha 1 of by-product root growth and reducing the incidence of ratoon decline. The objecgypsum into heavy-textured soils has been shown to tive of our research was to determine the effect of gypsum and comincrease sugar yields of ratoon sugarcane in Louisiana posted, municipal-biosolids application on root growth, crop yields, (Breithaupt et al., 1991), though it was not determined and leaf nutrient concentrations of sugarcane grown on a silty clay whether gypsum affected sugarcane root growth. loam soil. Gypsum mixed into the rows at 2.24, 4.48, and 8.96 Mg ha 1 Other research showed a yield increase of 15% in did not affect (P 0.05) root growth or cane and sugar yields. Likewheat (Triticum vulgare Vill.) and sorghum (Sorghum wise, both subsoiland within-row applied compost at a rate of 44.8 Mg vulgare Pers.) with gypsum addition (Thomas et al., 1995). ha 1 did not affect cane or sugar yields compared with the control. Gypsum increased Ca, S, Mn, and Zn leaf concentrations, but had Gypsum applied in irrigation water increased sugar yield no effect on N, P, K, Mg, Cu, and Fe concentrations. Subsoil and and juice extraction percentage of sugarcane (Kumar within-row compost increased leaf S concentration; within-row comet al., 1999). Gypsum also increased yield in corn (Zea post increased leaf K; and subsoil compost increased leaf Zn, but mays L.) and alfalfa (Medicago sativa L.) up to 50%. reduced leaf Mn compared with the control. Compost application did This yield response was partially attributed to higher not increase Mn, Cu, Fe, or Zn concentrations in sugarcane leaf tissue exchangeable Ca and S, and a complementary reduction beyond acceptable limits. Within-row applied compost reduced (P in exchangeable Al (Toma et al., 1999). 0.05) root surface area compared with the control, and reduced sugar Compost improves soil structure by enhancing aggreyields compared with the subsoil compost treatment. This suggests gate stability (Tate, 1987), which results in improved that, at the compost rate used in our study, subsoil rather than withinrow application of compost, is the preferred practice for sugarcane water holding capacity and aeration. Similarly, the benegrown on this soil. ficial effects of compost have been attributed to suppression of soil-borne diseases (Hoitink and Fahy, 1986), and to improved soil physical properties and nutrient availability (DeLuca and DeLuca, 1987). Yield increases S (interspecific hybrids of Saccharum spp.) is an important agricultural commodity in Louisiof various crops, including sugarcane, have been reana. In 2001, sugarcane was grown on 200 000 ha of land ported following addition of organic amendments to soil by 773 producers. An estimated 184 000 ha was har(Bevacqua and Mellano, 1994; Hallmark et al., 1995). vested for sugar, with a total sugar production of 1.41 Horticultural crop yields and quality have also been immillion Mg. Gross farm income from sugar and molasses proved with compost application (Roe et al., 1997). was $378 million for 2001. With respect to plant diseases, Zhang et al. (1996) Most sugarcane in Louisiana is grown on heavy-texobserved that compost enhanced crop resistance to sevtured soils that offer less than ideal conditions for growth eral diseases, including Pythium root rot and Rhizoctinia and function of the root system. Also, the sugarcane root rot. Dissanayake and Hoy (1999) found sugarcane crop cycle is frequently limited to 3 yr—a first-year growth increased in Pythium arrhenomanes–infested soil crop (plant cane) and two ratoon crops—because of a to which organic materials had been added. The level complex disorder known as ratoon decline. Though of microbial activity resulting from the application of many factors are involved, Carter (1977) suggested that the organic material was an indicator of the potential for excess soil moisture exacerbates ratoon decline. Hence, disease suppression. Compost addition was also shown cultural practices that improve the soil environment to reduce the number of lesion nematodes extracted could benefit root growth and sugarcane production. from crop roots (Abawi and Widmer, 2000). One such practice is the incorporation of CaSO4– To determine compost quality and safeness, roots and 2H2O (gypsum) into the soil. Gypsum application imshoots of plants treated with compost can be monitored proves soil structure in heavy-textured soil, so that water (Murillo et al., 1995). Also, compost serves as a reservoir infiltration and the ability of roots to penetrate the soil for nutrients, such as N, P, K, and Ca, as well as micro nutrients like Cu, Fe, Mn, and Zn, and can help stabilize R.P. Viator and J.L. Kovar, USDA-ARS National Soil Tilth Lab., soil pH (Stamatiadis et al., 1999). It is, therefore, neces2150 Pammel Dr., Ames, IA 50011-4420; and W.B. Hallmark, Iberia sary to evaluate micro nutrient accumulation in crops Res. Stn., P.O. Box 466, Jeanerette, LA 70544-0466. Joint contribution following compost addition since this can lead to micro from the Iberia Res. Stn., Louisiana Agric. Exp. Stn., Louisiana State nutrient toxicity and decline in crop quality and yield Univ. Agric. Center, Jeanerette, LA, and the USDA-ARS National Soil Tilth Lab., Ames, IA. Approved for publication by the Director (Rengel et al., 1999). of the Louisiana Agric. Exp. Stn. as manuscript no. 01-70-0274. ReOne problem that must be overcome if application ceived 1 Oct. 2001. *Corresponding author ([email protected]). of organic materials to large land area is to be realized is that of local supply. Also, with increasing amounts of Published in Agron. J. 94:1332–1336 (2002).