Economic and Agronomic Effects of Four Tillage Practices on Rice Produced on Saline Soils

Conservation tillage practices have come into greater use in recent years. However, studies have shown that using these practices in rice (Oryza sativa L.) on soils prone to salinity problems can reduce yields. An agronomic study was conducted during 1995 and 1996 at the University of Arkansas’ Pine Tree Branch Experiment Station near Colt on a soil complex consisting of a Calloway silt loam (fine-silty, mixed, active, thermic Glossaquic Fragiudalf), Calhoun silt loam (fine-silty, mixed, active, thermic Typic Glossaqualf), and Henry silt loam (coarse-silty, mixed, active, thermic Typic Fragiaqualf), in areas that had a history of salinity damage to rice. The experiment was arranged in a randomized complete block design with three replications and four tillage treatments (conventional tillage, deep tillage with a paratill implement, attempted deep tillage with a chisel plow, and no-till) per replication. Enterprise budgets were used to determine the relative profitability of the four tillage systems (conventional, no-till, chisel plow, and para-till), in order to determine whether or not the increased production costs incurred using tillage would be offset by increased returns. Sensitivity, breakeven, and statistical analyses were performed to determine whether there was any significant difference in yields and net returns among tillage practices. No significant difference was demonstrated among the three treatments using tillage; no-till, however, was significantly different from the other three, having considerably lower yields. When averaged across years and treatments, yields from tilled plots averaged 72.15 cwt/acre. Yields from no-till plots averaged 62.37 cwt/acre. Net returns above total costs for tilled plots, when averaged across years and treatments, averaged $230.25/acre. Net returns above total costs for no-till averaged $173.03/acre. It is therefore recommended that some form of tillage be used in order to reduce the concentration of salts in the rice root zone. However, it is not possible to recommend one form of tillage as being superior to the others examined in this study. Research QuestionConservation tillage practices, such as no-till and reduced-till, have come into greater use in recent years. While these practices can decrease soil loss to erosion, and in some cases reduce production costs, studies have shown that using these practices in rice on soils prone to salinity problems can reduce yields. The use of tillage on saline-prone soils has been shown to reduce salinity damage during the seedling growth stage. The objectives of this study are to evaluate the effects of various tillage systems on salinity stress and yield on rice; to evaluate the effects of various tillage systems on salt movement within the soil profile; to ascertain the relative profitability of four tillage procedures, and to determine whether the net returns from those tillage practices with improved yields are sufficient to cover the additional expenses associated with these practices. Literature SummaryThere have been very few studies on the effects of tillage in rice. It has been shown that yield, N, and P contents tended to be enhanced by low salt concentrations, but depressed at high concentrations. Chloride salts were most detrimental, while sulfate salts were beneficial when concentrations of electrolytes and P in the soil were not high. It has also been shown that deep tillage can eliminate mechanical impedance to root growth and lowers susceptibility of subsoil N to various loss mechanisms. The only available study with economic analysis found that rice grown in reduced- and no-tillage systems produced grain yields comparable to those of rice grown in conventional tillage systems. However, net returns from the reduced- and no-tillage systems were higher than for the conventional tillage system due to lower direct expenses. This experiment, however, was not conducted on saline soils. Study DescriptionThe agronomic experiment was conducted during 1995 and 1996 at the University of Arkansas’ Pine Tree Branch Experiment Station near Colt on a soil complex consisting of a Calloway silt loam, Calhoun silt loam, and Henry silt loam, in areas that had a history of salinity damage to rice. The experiment was arranged in a randomized complete block design with three replications and four tillage treatments (conventional tillage, deep tillage with a paratill implement, attempted deep tillage with a chisel plow, and no-till) per replication. Using data from the agronomic experiment, enterprise budgets were generated to calculate expenses and net returns. Sensitivity, breakeven, cross-breakeven, and statistical analyses were conducted using the yields and net returns above direct and total costs from the enterprise budgets. Applied QuestionsAre the returns from the increased yields observed with tillage sufficient to offset the costs of tillage? On average, net returns above direct expenses and net returns above total expenses were higher for treatments using tillage, as opposed to no-till. The Duncan Multiple Range Test shows that on average, net returns from the no-till treatments were significantly different from those of the tilled treatments. Are any tillage treatments superior to the others in terms of yields and net returns? The Duncan Multiple Range Test shows no significant difference in yields, net returns above direct expenses, or net returns above total expenses from any of the three treatments (conventional tillage, paratill, and chisel plow) using tillage. Table 1Yields and net returns above total expenses (NRAT). 1995–1996Yield, cwt/acreNRAT, $/acreTillage treatmentMean†Standard deviationMean†Standard deviationConventional till71.59 (a)6.87232.89 (a)144.31Chisel plow71.14(a)6.51224.31 (a)137.09Para-till73.73 (a)2.38233.56 (a)124.26No-till62.37 (b)11.55173.03 (b)136.04†Duncan Multiple Range Test. Means with the same letter are not significantly different at the 0.05 level.