Concurrent recurrent selection experiments were conducted for five cycles to compare three methods of selection for grain yield in maize (Zea mays L.): (1) combining ability with an inbred line (Inbred Tester Method), (2) combining ability with the broad‐base parental population (Parental Tester Method), and (3) yield S2 lines per se (S2 Progeny Method). The 15 selected populations were then crossed with the parental population and with another broad‐base synthetic to evaluate changes in general combining ability, and also were tested as randommated and selfed populations per se.A significant linear increase in general combining ability over cycles was obtained for all methods, but the Inbred Tester Method was significantly more effective than the other two methods (4.4% gain per cycle, compared with 2.4 and 2.0% for the Parental Tester and S2 Progeny Methods, respectively). There was no significant difference among methods for yield of random‐mated selected populations when adjustments were made for differences in rate of inbreeding.The results indicate that the inbred tester used was homozygous recessive at many important loci. This would result in larger testcross variances and more successful selection of dominant favorable alleles than is possible with a broad‐base tester, which probably has intermediate gene frequencies at most loci. The slow progress in combining ability improvement with the S2 Progeny Method suggests that this method also was not effective in fixing dominant favorable alleles.

The quantities of municipal wastes are so large that croplands have been considered as possible sinks for their disposal. In this study large amounts of liquid‐digested sludge were applied to the soil. The accumulation and distribution of its constituents in the soil profile were studied.The sludge contained 2.6 and 3.0% dry matter and very little Cd and other toxic metals. Liquid sludge equivalent to 0, 87, 174, 241, 288, and 335 metric tons/ha of dry matter was applied to each of three Paleudults (Orangeburg fine sand loam [fsl], Lucy fsl, and Troup fsl) over a 6‐year period. Soil samples, to a depth of 150 cm, were obtained 1 year after the last sludge application to determine nutrient and organic matter movement.Sludge applications increased soil organic matter to a depth of 90 cm in Orangeburg fsl and Troup fsl, but had no consistent effect on Lucy fsl. About 50% of the applied organic matter was oxidized, forming acids that lowered the soil pH.Double acid extraction of Orangeburg fsl indicated that Ca, Mg, and to some extent K, moved below the 90‐cm depth of the soil profile. Lesser amounts leached from the 90‐ to 120‐cm layer, and no detectable amounts leached from the 120‐ to 150‐cm layer. Extractable Fe and Al increased to the 90‐cm depth. Extractable Cu remained in the top 30 cm and Zn in the top 90 cm of the profile.Similar results were found in a 5N HCl digest except that P was significantly increased by sludge application and accumulated largely in the surface soil.

Diagnostic criteria for monitoring the N status of both soil and cotton plant are needed to aid in adjusting N fertilization to compensate for seasonal variations. A 3-yr study was initiated in 1981 to determine the feasibility of using soil and petiole N03 -N testing as an aid in cotton (Gossypium hirsutum L.) lint production along the Gulf Coast. A factorial experiment with four rates of N, three rates of K, and four replications was established on an Orangeburg fine sandy loam (fine-loamy, siliceous, thermic Typic Paleudult). Soil samples were taken each year just prior to the addition of N and K fertilizer treatments. Response to K fertilization was not significant. Cotton petiole samples were taken on selected plots for 9 weeks beginning 1 week prior to first bloom. The response to N resulted in a 3-yr average maximum yield of 1294 kg ha-• of lint cotton from 114 kg ha -• of applied N. Petiole analyses for N03 -N indicated that additional N should be applied to all treatments after the second week of petiole sampling, even though lint yields were above average in this study (average yield for this soil is 1008 kg ha-1 ). This suggests that the sufficient-N zone established for petiole analyses of N03 -N in Arkansas and accepted in Georgia is higher than is desirable for thermic Typic Paleudults. Repeated applications of N to the soil over the 3 yr of the experiment did increase the amount of N03 -N extracted from the soil indicating that some of the applied N was not used by the cotton plant. A revised N03-N sufficient-N zone, developed by Georgia researchers and first used in 1985, conforms with the data presented in this paper and could be used satisfactorily to determine N recommendations from petiole analyses for cotton lint production on thermic Typic Paleudults of the Gulf Coast of Florida.

To obtain additional information on the effectiveness of recurrent selection for specific combining ability in maize (Zea mays L.), we evaluated seven cycles of selection for combining ability with the single‐cross tester F44 ✕ F6. Grain yield, lodging resistance, and low ear height were the main selection criteria.Seed of the selected population from each cycle was stored and later evaluated for combining ability with the original tester, F44 ✕ F6, and with an unrelated synthetic. The evaluation with F44 ✕ F6 indicated that the seven cycles of selection resulted in 18% more grain yield, 9% lower ear height, and 35% less lodging. Performance was similar when the same selected populations were crossed with an unrelated synthetic. This suggests that gains for all traits resulted from increasing the frequency of genes with additive effects.These results and others previously reported for inbred testers suggest that narrow‐base testers are effective for improving general as well as specific combining ability, and that it is possible to change such testers in a recurrent selection program with little loss in accumulated improvement.

Enteroviruses associate with aerobically and anaerobically digested sludge were determined before the addition of the sludge to a sludge lagoon. The fate of sludge-associated viruses was followed during detention of sludge in the lagoon and after application of sludge to land for disposal. While digested sludge was being added to the lagoon, enteroviruses were readily detected in grab samples of sludge from the lagoon. Sludge-associated viruses dropped to low or undetectable levels after disposal of sludge on land and during periods when addition of digested sludge to the lagoon was suspended. Changes in the levels of fecal coliforms in the lagooned sludge paralleled changes in the numbers of enteroviruses. Enteroviruses were not detected in water from deep wells located on the sludge disposal site or near the lagoon. During the initial part of the study, poliovirus serotypes accounted for greater than 90% of the viruses identified. Later, poliovirus serotypes comprised less than 40% of the virus isolates, and echoviruses and Coxsackieviruses were the most common enteroviruses identified.