The seriousness of a disease is reflected in the amount of yield reduction caused by the disease under field conditions. We wished to obtain data on the amount of yield loss of corn (Zea mays L.) caused by the corn stunt disease complex which includes the maize chlorotic dwarf virus (also referred to as Ohio corn stunt agent) and the Mississippi corn stunt agent, believed to be a mycoplasma; and to determine if time of initial disease symptoms influences the amount of yield reduction. Corn hybrids were subjected to natural infection under field conditions during 5 years. Plants showing disease symptoms were tagged and yields from these plants were compared with plants not showing disease symptoms. Yields from diseased plants were less than 50% of those from healthy plants in each of the 5 years. The number of ears and kernels per plant was reduced more than was the weight of kernels on the diseased plants. Plants showing disease symptoms early in the season were more severely affected than plants that developed symptoms later. From our data, we concluded the following: diseased plants showing symptoms as early as 52 days after planting would produce no grain; plants showing first symptoms as late as 107 days after planting would produce normal yield; between the two extremes the yields on diseased plants would be reduced by 1.82% of that on healthy plants for each day the first symptoms appeared earlier than 107 days after planting.

Double‐cropping systems involving no‐till planting are becoming popular in the southeastern USA, but adequate management practices have not been developed. Therefore, this study was conducted to determine the effects of the following tillage systems. Corn [Zea mays (L.)] and grain sorghum [Sorghum bicolor (L.)] were planted without tillage following winter wheat [Triticum aestirum (L.)] or barley [Hordeum vulgate (L.)] and with conventional tillage following previous summer crop at two locations in Georgia for 4 years with and without irrigation. Corn and grain sorghum yields did not differ significantly for conventional tillage and no‐till plantings made on the same date. No‐till corn and grain sorghum produced higher yields when early planted (after small grain for forage) than when late planted (after small grain for grain). Irrigation increased conventionally tilled corn yields by 31% (at Experiment) and grain sorghum yields by more than 20%. The smaller increases observed for irrigated early‐planted no‐till corn and grain sorghum were attributed to a higher soil water content on nonirrigated no‐till. Irrigation did not increase yields of late planted no‐till corn and grain sorghum due to interfering biological factors.

Since numerous small grain producers desire to make fall application of efficient levels of N for maximum yields, studies are needed to determine the efficiency of fall‐applied N (with and without an inhibitor) vs. split N applications. Field studies were conducted at two locations each year over a 3‐year period with the objective of evaluating the response of wheat (Triticum aestivum L.) to N rates, time of application, and effect of a nitrification inhibitor on soils of different characteristics (Typic Hapludult and Typic Paleudult). Yields, tissue concentrations of various elements, grain analyses, and soil NH4‐ and NO3‐N were evaluated. Splitting the N, 28 kg/ha in the fall and 56 kg/ha topdressed in the spring, was superior to applying all the N in the fall. The inclusion of the nitrification inhibtor, 2‐chloro‐6‐(trichloromethyl) pyridine (N‐Serve), with ammonium sulfate in the fall at the rate of 84 kg/ha did not influence yields or N levels in the tissue or grain. The inhibitor had no effect on elements other than N. Although the nitrification inhibitor influenced the retention of the NH4‐N in the soil until the January sampling, this retention was not evident for either soil at the March sampling. Therefore, we concluded that the N applied as a part of the complete fertilizer at the rate of 28 or even 84 kg/ha in the fall is inadequate for maximum wheat yield in either the coastal plain or piedmont regions of Georgia. A nitrificaton inhibitor applied with the ammonium sulfate was ineffective in preventing nitrification of the ammonium nitrogen or to increase yields.

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