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Tillage to disrupt root-restricting, consolidated soil zones can improve rooting capacity and crop production, but costs increase with the need for more powerful tractors. Between 1992 and 1996, agronomic and economic consequences of annual or less frequent soil disruption treatments were evaluated for cotton (Gossypium hirsutum L.) on a Typic Kanhapludult. Two soil-disruptive treatments, fall paratillage (PT) and in-row chisel (IC) at planting (spring), were compared with two shallow-tillage treatments, coulter planting plus weed control with sweeps (ST) and conventional disk tillage (DT). The IC, PT, and ST treatments were applied annually or in Years 3, 4, and 5. Lint yield with annual IC was 15 to 20% greater than with DT each year. In 1994, yields ranged from 0.53 to 0.84 Mg ha -1 with annual IC and were better than with annual ST or PT. In 1995, yields ranged from 0.92 to 1.29 Mg ha -1 , with the top yield associated with current-year IC application. In 1996, no differences in yield were observed among tillages; however, yields of two IC treatments were among the top five. For Years 3, 4, and 5, cotton yields were numerically greater with annual IC than with annual PT and ST. Yields with PT, ST, and DT were not different. Average annual net returns from annual IC were $450, $403, and $287 ha -1 greater than those with annual DT, PT, and ST, respectively. In-row chisel appears to be a more economically viable production practice for heavy Piedmont soils compared with PT, ST, and DT.

Little information exists on the biogeochemical effects of combining no-tillage planting with paraplowing (to improve deep water penetration) or with secondary tillage (to control weeds). We determined surface residue and soil C and N pools (total, particulate, microbial biomass, and mineralizable) and water-stable aggregation at depths of 0 to 25, 25 to 75, and 75 to 150 mm from a Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludults) in Georgia, Soil tillage treatments were a factorial arrangement of tillage type [(i) minimal disturbance with in-row chisel at planting, (ii) no-tillage planting with autumn paraplow, and (iii) no-tillage planting with secondary tillage during the summer] and tillage frequency [(i) every year, (ii) every second year, and (iii) every fourth year I. No-tillage planting without further disturbance occurred in remaining years. At a depth of 0 to 25 mm, basal soil respiration averaged 9 mg kg -1 d -1 with conventional tillage, 27 mg kg -1 d -1 with no-tillage planting and soil disturbance every year, and 36 mg kg -1 d -1 with no-tillage planting and soil disturbance every fourth year. At a depth of 0 to 150 mm, mean-weight diameter averaged 1.03 mm with conventional tillage, 1.12 mm with paraplow, 1.17 mm with secondary tillage, and 1.23 mm with in-row chisel. No-tillage planting with alternative tillage types and frequencies not only improved surface soil properties compared with conventional tillage, but also improved seed cotton yield an average of 19%, Biophysical improvement of surface soil structure would presumably lead to greater water infiltration and improved water use efficiency in the long term.

The elemental concentration of K, Na, P, Ca, Fe, Mg, Cu, Zn, and Mn was determined in seeds of three cultivars of cowpeas [Vigna unguiculata (L.) Walp.] treated with 0, 2000, and 4000 ppm simazine as a foliar spray and side dressed with 0, 30, and 60 kg/ha ammonium nitrate fertilizer. The element Ca was increased by the simazine treatment in‘Pinkeye Purple Hull’and Mn was increased by the ammonium nitrate fertilizer treatment in‘Mississippi Silver’. Significant fertilizer by simazine interactions were found with the remaining elements. Similar treatment responses in the elemental concentration were found among the three cultivars. The percentage recommended dietary allowances based on the individual elemental concentrations that a 100s raw edible portion of cowpeas would supply were not significantly affected by the treatments.

In the Piedmont of the Southern Appalachian region, soil degradation is most often expressed by crop water deficit that limits crop yield in the warm season. To evaluate the nature of variability on these cropped lands, soybean [Glycine max (L.) Merr.] yield and associated soil characteristics were measured across the range of surface soil conditions in 40 farm fields. Factor analysis of the data permitted identification of variables responsible for most of the yield variability. Carbon in the surface soil was identified as the manageable soil variable that could significantly influence crop water availability and curtail soil erosion. Subsequently, selected crop cultures that supplied a range in quality and quantity of crop biomass to the soil surface were applied on three soil erosion classes for 5 yr. Large increases in rainfall infiltration and reduced soil erodibility were associated with no-till planting of grain sorghum [Sorghum bicolor (L.) Moench] into crimson clover (Trifolium incarnatum L. Tibbee) in comparison to conventional tillage of grain sorghum and soybean. The maintenance of a decomposing mulch by crop residue additions of about 12 Mg ha -1 yr -1 generated high soil C levels in the 0- to 15-mm depth and a high water stability of aggregates in the 0- to 80-mm depth in comparison to incorporated crop residues. In the 6th yr, grain yield of conventionally tilled soybean was 30 to 100% greater on the previously no-till crop culture than on the conventionally tilled. The restoration and maintenance of soil productivity commensurate with inherent site resources was associated with maintenance of a decomposing mulch on the soil surface derived from an appropriate quantity and quality of crop residue produced in situ.

Summary: Resume: Zusammenfassung Field experiments were established at the Southern Piedmont Research facility near Watkinsville, GA during 1989 and 1990 to assess the critical period of interspecific interference between different Cynodon dactylon (coastal bermudagrass) densities and cotton (Gossypium hirsutum) in a conservation-tillage system. Cotton was exposed to coastal bermudagrass for 0, 4, 7, 10 and 25 weeks. Cotton height, yield, and soil volumetric water content were examined. Volumetric water content was determined by time domain reflectometry. Cotton height and yields were significantly reduced by exposure to coastal bermudagrass and reduction in cotton productivity increased with increasing coastal bermudagrass density. Soil volumetric water content decreased in the upper 30 cm of soil with increasing coastal bermudagrass density. The critical period of coastal bermudagrass in cotton was determined to be 4 to 7 weeks after planting. Relations entre l'humidite su sol et la periode critique de competition de Cynodon dactylon (L.) dans du coton en systeme de labour (Gossypium hirsutum L.) Des essais de plein champ ont ete mis en place sur le centre de recherche du Sud-Piemont pres Watkinsville, GA pendant 1989 et 1990 pour evaluer la periode critique d'interference interspecifique entre differentes densites de Cynodon dactylon et de coton (Gossypium hirsutum) dans un systeme de labour. Le coton a ete expose au cynodon pendant 0, 4, 7, 19 et 25 semaines. La hauteur du coton, le rendement et la teneur en haut du sol ont ete examines. Le volume d'eau du sol a ete determinee par reflectometrie. La hauteur du coton, et les rendements ont ete reduits significativement par l'exposition au cynodon et la reduction de productivite du coton a augmente avec l'augmentation de la densite du cynodon. Le volume d'eau du sol dans les 30 premiers centimetres a diminue avec l'augmentation de la densite du cynodon. La periode critique du cynodon pour le coton a ete determinee comme se situant 4 a 7 semaines apres la plantation. Konkurrenz von Cynodon dactylon (L.) Pers. mit Baumwolle (Gossypium hirsutum L.) bei konservierender Bodenbearbeitung — Kritische Periode und Bezug zur Bodenfeuchte Zur Ermittlung der kritischen Periode der Konkurrenz von Cynodon dactylon (L.) Pers. mit Baumwolle (Gossypium hirsutum L.) bei konservierender Bodenbearbeitung wurde die Kultur in Feldversuchen 1989 und 1990 auf der Piedmont-Versuchsstation fur 0, 4, 7, 10 und 25 Wochen mit dem Unkraut in unterschiedlicher Dichte wachsen gelassen. Hohe und Ertrag der Baumwoll-Pflanzen wurden durch die Verunkrautung signifikant reduziert, und mit steigender Unkrautdichte nahm die Produktivitat genauso wie die Bodenfeuchte in den obersten 30 cm ab. Die kritische Periode der Konkurrenz zwischen dem Unkraut und der Kulturpflanze lag zwischen der 4. und der 7. Woche.

Chisel tillage to alleviate soil compaction problems is known to provide significant benefits, but the required frequency of chisel tillage is not known. This study was designed to seek information on the required frequency of chisel tillage in moderately and severely eroded soils, using penetrometer cone index and water infiltration rate to quantify soil condition and a paratill as the chiseling tool. The cone index and water infiltration results indicated that in either the moderately or severely eroded soils used in this study, chiseling needs to be conducted annually, especially on severely eroded soils, to ensure minimizing the effect of soil compaction on crop growth.

Soil loss from and rainfall retention on cropland during individual seasons vary from year to year. To quantify this variability for evaluation of soil and water related risks for different seasons and crops, probability distributions of soil loss and rain water retention are needed. In this study, probability distributions of soil loss and rainfall retention rates were computed using rainfall, runoff, and soil loss data from three field watersheds with Cecil-Pacolet soil (Typic Hapludults) in the Southern Piedmont of the United States. Long-term (34-year) rainfall records from a nearby gage were included in the computations. Resulting probability distributions were compared to evaluate risks of soil loss and low rainfall retention for different seasons and crops. Risks due to watershed differences in slope and in terrace and waterway conservation practices were also compared. These comparisons showed that soil loss risks are greater for the summer than for the winter crop season and greater for soybean (Glycine max. L. Merr.) than for corn (Zea mays L.). Considerable soil loss risk reduction was also observed for watersheds with less land slope and with terrace and grassed waterway installation. Risk of low rainfall retention was found to be less for the winter crop season than for the summer season. Rainfall retention risks for the winter crop season appeared to be unaffected by crop and watershed differences. For the summer crop season, however, risk of low rainfall retention was observed to be slightly higher for soybean than for corn and slightly lower for fields with terraces, grassed waterways, and lesser slopes. Soil loss and rainfall retention risks computed in this study can be coupled with economic costs for crop production and conservation planning.

Cone index measurements of experimental field plots after eight years of three constant traffic-tillage systems showed low variability in soil zones unaffected by tillage or traffic. There were significant differences in cone index in soil zones directly affected by tillage and traffic. The results support the concept that much of the variability in cone index under field conditions is caused by tillage and traffic as opposed to soil heterogeneity. The results imply that by taking closely spaced samples, and having a knowledge of how cone index relates to traffic and tillage, the previous traffic-tillage history of a soil can be assessed.

Rainfall and runoff event data from several different cropping and tillage systems on three field-sized watersheds in the Southern Piedmont of the U.S.A. are used to estimate empirical probability distributions of the USDA Soil Conservation Service runoff curve number. Long-term rainfall records from a nearby gauge are also employed to obtain probabilities for rainfall event occurrence and depth. These probability distributions of runoff curve number and rainfall occurrence and depth are incorporated in a recursive computer procedure to compute estimated probability distributions of annual rainfall retention for the different cropping-tillage systems. Comparison of these estimated rainfall retention probability distributions shows a reduction in the risk for low rainfall retention with the installation of conservation tillage systems.

SOIL erosion control of row-cropped, Southern Piedmont lands is a constant problem. A 2.71 ha (6.70 acre) watershed, with an average slope of 3.4 percent, was equipped with a 0.76 m (2.5 ft) H-flume in summer of 1972 to study runoff and soil losses from row crop land. The watershed treatments were con-ventional till, without terraces or grassed waterways, during the first 2 yr in a soybean {Glycine max (L.) Merr.)-fallow sequence, and then 2 yr of no-till double cropped barley (Hordeum vulgare L.), followed by grain sorghum {Sorghum vulgare Pers.) with fescue {Festuca arundinacea Schreb) grassed waterway. Annual runoff was decreased from 22.5 cm (17.6 percent) with con-ventional tillage to 12.0 cm (9.7 percent) with double cropped, no-till practices. Runoff was reduced 90 percent during the vulnerable sediment and chemical transport season of May, June, and July. Annual flume-measured sediment decreased from 26.26 t (metric tons)/ha (11.71 tons/acre) with conventional tillage to 0.13 t/ha (0.06 ton/acre) with no-tillage. Soil loss values associated with no-tillage show that crop row direction is not important when no-tilling is accom-panied with grassed waterways in the Southern Piedmont. Barley and grain sorghum both produced 15.43 t/ha (6.88 tons/acre) of grain during the no-till period. Annual erosion, estimated by the Wischmeier-Smith erosion equation (WSEE), was 71.23 t/ha (31.80 tons/acre) and 1.30 t/ha (0.58 ton/acre) for conventional and no-till, respectively.

Southern pea seeds were grown 2 yrs with treatments of ammonium nitrate fertilizer 0, 30, and 60 kg/ha and simazine 0, 2,000, and 4,000 ppm applied as a foliar spray. Yield, proximate analysis, amino acid content, and protein quality were determined. No differences were found in yield, crude fat, and crude fiber. Ash, protein, and several of the amino acids increased with the 30 and 60 kg/ha nitrogen fertilizer treatments. Treatments with simazine had no effect on the essential amino acid content. In the Southern pea seeds, protein quality was decreased by the treatments with nitrogen fertilizer, simazine, and combinations of these treatments.

An approach and methodology for characterizing behavior of crop-soil systems as they may be modified by soil erosion were applied to a Cecil-Pacolet soil (clayey, kaolinitic, thermic Typic Hapludults) landscape cropped to soybeans [ Glycine max (L.) Merr.]. In each of two years crop and soil measurements along with determination of slope and landscape position were made on slightly, moderately and severely eroded sites in 24 farm fields of which 8 were common to both years. Daily rainfall was recorded during the crop season on each field. Among the 40 variables selected to characterize the system behavior were dynamic or within-season, among-season, and static variables. Search for and identification of variables which determine most of the soybean yield variability have been adopted as the primary objectives in determining behavior of the crop-soil system. Recognizing the strong functional dependencies among a number of the variables, we used multivariate statistical procedures that are based upon eigenvalue-eigenvector analysis of the matrix of correlation coefficients among all variates. Results of using factor analysis and components regression to identify variate contributions to yields of soybeans are reported. In linear, non-interactive analyses, variate contributions to yield were evaluated. The major contribution of clay and organic carbon contents in the surface 0.1 m of soil to soybean yield variations in both seasons identifies soil water as the regulating variable.

Selective management practices were used on two upland Southern Piedmont watersheds to assess their influence on overland transport of Cl, soluble-N, and total Kjeldahl-N (TKN). Ammonia-N and TKN were measured in both runoff water and sediment phases and related to these transport modes. Chloride (112 kg Cl/ha) served as a tracer anion because of its inert biological activity. Optimum rates of N-fertilizer (∼140 kg N/ha) were applied in recommended split-applications for corn growth. Annual NH₄-N and TKN losses were 35 to 40% less when associated with terraces and double cropping of corn (Zea mays L.) and winter rye (Secale cereale L.) than from a watershed without conservation practices. This difference was related primarily to differences in sediment yield from the two watersheds. No real annual differences were detected for Cl and NO₃-N losses between watersheds. Total seasonal nutrient losses were strongly affected by the quantity of sediment transported during highly erosive periods of May, June, and July. Chloride and TKN concentrations in runoff were more constant among cropping seasons; therefore, individual storm yields were best related to runoff water volume. Nitrate-N and NH₄-N concentrations in runoff decreased rapidly during corn canopy development causing the quantity of these N species to be best related to sediment transport. An inadequate number of runoff storms occurred during these short periods of high soil chemical concentrations, derived from Cl- and N-fertilizer sources, in the surface depth (0 to 8 cm) to significantly develop a relation to runoff concentrations. Runoff water and sediment variation accounted for 82 to 93% of nutrient loss variation on the nonconservation watershed. The same variables accounted for as little as 61% of the nutrient variation on the conservation watershed. Runoff losses of plant nutrients may be reduced by shifting most of their application to periods of rapid plant canopy development and periods of less intense rainfall.

An understanding of N cycling in the soil-plant-atmosphere components of wheat (Triticum aestivum L.) production systems is necessary to maximize yield and quality. The objectives of this study were to examine N cycling and observe the effects of N surplus and deficit on N absorption/desorption in the soil and atmosphere and to evaluate translocation within the plant. Soil, plant, and microclimate measurements were taken concurrently, and soil, plant, and atmospheric ammonia (NH₃) transport determined. During the early vegetative phase, plant N concentration reached a maximum; however, during the remaining growth periods, N concentration decreased even though N uptake from the soil continued until plant maturity. More total N was translocated to grain from leaves than stems, and translocation from the leaves began earlier than that from stems. Isotope and total N studies showed that after anthesis about half of the grain N came from remobilization from leaves and stems and the other half directly from the soil. A progressively larger percentage of N came from mineralized organic matter as the season progressed. Nitrogen was lost as volatile NH₃ from the plant after fertilizer application and during the senescence period. Prior to anthesis, atmospheric NH₃ absorption was observed during a period when soil N was temporarily unavailable. About 21% equivalent of the applied fertilizer was lost as volatilized NH₃. During the period of soil unavailability an amount equivalent to about 1% equivalent of the applied fertilizer was gained from atmospheric NH₃ by plant absorption.

Runoff and persistence of selected herbicides were studied on four small Piedmont watersheds in Georgia during four growing seasons. This is part of a study designed to provide data for developing and testing mathematical models for agricultural chemical transport. Seasonal runoff losses were determined relative to watershed management, herbicide type and persistence, mode of application, and time of runoff in relation to application timing. Seasonal losses were usually < 2% of the application, unless large runoff volumes were generated shortly after application. Average storm herbicide concentrations in runoff were correlated with herbicide concentrations at the 0- to 1- cm depth increment of the watershed soils at the time of runoff. Paraquat concentrations in runoff (predominantly sediment associated) were well correlated and positive with the product of soil herbicide concentration and sediment in runoff. Equations describing soilbased herbicide transfer to runoff were power functions with exponents near unity with the form: Y = a xᵇ. Simple relationships such as those developed in this study along with hydrology and erosion/sediment models may he useful in predicting pesticide runoff potential when assessing relative impacts of management decisions. The next step would be to describe key management practices in terms of these coefficients and exponents.

(…) Soybean growth and N uptake characteristics were similar in both tillage systems, except during a 14-d drought period, which caused water stress in the CT system, but not the NT system. Nitrogen fixation decreased in the CT system to less than half that of the NT system fixation rate, resulting in a seasonal reduction of 29% in the CT system (…)

PRACTICAL application of seasonal risk analysis for soil conservation planning is illustrated. Applicability is demonstrated by quantifying potential reduction in soil loss through seasonal adjustment of agronomic practice. The method is dependent upon seasonally continuous probability distributions developed earlier. The erosion index (EI) and the cover and management factor (C) of the Universal Soil Loss Equation were selected to quantify soil loss calculations. By randomizing these two variates soil loss by both seasonal pattern and annual total was simulated for 12 different agronomic practices. Reduction of soil loss was expressed in terms of expectation (risk) and in terms of variability of that expectation (uncertainty). Utilizing the simulated soil losses the utility of incorporating seasonal variability in management options to facilitate conservation planning is demonstrated.

Studies were conducted to evaluate the use of a solid‐state chloride electrode for chloride determinations in soil extracts. The solid‐state chloride ‐electrode was used as an end point detector in the titration of chloride with AgN03 and direct reading of chloride in solution. The solid‐state electrode gave results very similar to those obtained with a silver electrode (r = 0.999) when used as an end point detector. Values obtained using the solid‐state electrode as a direct reading electrode were also well correlated (r = 0.998) but were slightly higher than results obtained by titration with a silver electrode.

Effects of three plant densities and two nitrogen rates on leaf areas and nitrogen uptake by tobacco plants were studied during 1961 and 1962. A study was also made on the economics of these treatments.Leaf area indices (LAI's) for both years increased with time until the reduction in total leaf area through loss of senescent lower leaves became greater than the gain in leaf area of the active upper leaves. The highest maximum LAI of 5 in 1961 was obtained for the high nitrogen rate and the 25-cm spacing. The lowest maximum LAI of 2.5 was obtained for the low nitrogen rate and the 76-cm spacing. LAI's increased with high nitrogen and at both levels of nitrogen the LAI's were in the order of 25 > 51 > 76-cm spacings in 122-cm beds.Relationships between leaf area and leaf weight per plant were very similar during 1961 and 1962. Correlation coefficients for leaf areas and weights varied from 0.95 to 0.99 in 1961 and from 0.92 to 0.99 in 1962. In both years, better correlation appeared between leaf areas and weights at the high nitrogen rate than at the low nitrogen rate, with spacing treatments having little effect on the relationships.Nitrogen uptake was much higher with the high nitrogen treatment than with the low nitrogen treatment.The yield of flue-cured tobacco increased with closer plant spacing and the higher nitrogen rate. However, leaf quality decreased with the high nitrogen rate and offset the higher yields in total dollar value per hectare. The quality of tobacco appeared to be influenced more by the nitrogen application than by the different plant spacings~ The most profitable treatment combination appeared to be the 76-cm spacing at the low nitrogen rate.

Legumes are commonly used to provide nitrogen (N) for succeeding crops, but the net gain in N to the system is rarely measured. This study developed a N budget for a winter legume production system to estimate sources, sink, and net system gain in N. Crimson clover (Trifolium incarnatum L.) reseeded from the preceding year and was killed with herbicide the following spring. A forage sorghum crop (Sorghum vulgare Pers.) was planted and harvested twice during the summer. Subplots were sampled at frequent intervals throughout the growing seasons for measurements of plant biomass and N content (leaves, stems, seeds, roots, and litter) and soil mineral N. During the clover growing season, soil N mineralization and leaching rates were estimated with an in situ chamber technique, and aerial ammonia (NH 3 ) transport measurements were made biweekly by micrometeorological techniques. Nitrogen in the clover crop increased until anthesis, and then declined slightly prior to dessiccation with herbicides. Total N accumulated in the clover at dessiccation was 323 kg N ha −1 (28 in leaves, 81 in stems, 40 in seeds, 44 in surface-layer roots, and 130 in dead leaves and litter). Aerial NH 3 absorption by the clover was small during the growing season (0.18 kg N ha −1 ) but NH 3 loss from the killed clover was also minimal (0.25 kg N ha −1 ) and occurred during the period shortly after herbicide application. The summer sorghum crop took up 454 kg N ha −1 over the course of two cuttings from the soil mineral and mineralized organic N resource plus atmospheric NH 3 and other atmospheric N inputs such wet and dry deposition. Total N accumulated by the clover from N fixation, soil mineral N uptake, and NH 3 absorption provided the equivalent of 70% of N removed by the sorghum crop

Sorghum and soybean were as summer crops in double-cropping systems with winter wheat on southern Piedmont soils. Wheat following sorghum had significantly less take-all than wheat following soybean over three growing seasons at two sites. Site one had no history of take-all and site two had a history of severe take-all. Sorghum also reduced take-all on wheat when grown as the summer crop in 2 of the last 3 yr compared with a continuous soybean summer crop at site one. (…)