The rolling soils of the Southern Piedmont are highly erosive when clean tilled. The area is well adapted to close‐growing forage crops, but the thriving poultry industry in this region needs more grains. By combining no‐till corn (Zea mays L.) production on fescuegrass (Festuca elatior, var. arrundinacea) sod with irrigation and adequate fertilization, a number of problems might be solved. Corn was grown on Cecil sandy loam following corn and in live fescuegrass with and without irrigation in 1969, and by no‐till planting in live, stunted, and killed fescuegrass with and without irrigation in 1970. Nitrogen rates applied to the corn were 148 kg/ha in 1969 and 112, 224, and 448 kg/ha in 1970. Without irrigation, the corn and the live grass exhausted all available soil water during droughts in June, and the corn died. Corn growth in the stunted and killed sods was reduced, but the plants lived. With irrigation the corn and live grass used soil water faster than corn in dead sod until the corn developed a complete canopy. After the canopy developed, corn in killed sod used more soil water than did the corn in live sod. Without irrigation, corn yields were O with live sod and about 1000 kg/ha on killed sod and showed no response to N levels of 112, 224, and 448 kg/ha. With irrigation, yields were directly proportional to N levels and to the amount of live sod; yields ranged from 140 kg/ha with 112 kg/ha N on live sod to 9,980 kg/ha with 448 kg/ha N on killed sod. The excellent yields from corn in grass sod show that corn can be grown on the sloping fields of the Piedmont and related areas to fill the grain needs there without causing serious soil erosion.
The soil and nutrient losses in runoff for selected cropping systems were studied using artificial rainfall techniques on three soils in Puerto Rico in 1967. This study was undertaken to determine the erosion control effectiveness of and nutrient removal in runoff from selected cropping systems. Soils were Humatas clay, Juncos silty clay, and Pandura sandy loam. Artificial rain was applied at 6.4 cm/hr fox 60 rain (Storm 1), followed 10 min later by 12.7 cm/hr for 60 min (Storm 2). Storms and 2 were combined and designated storm 3, representing less than 2‐ to more than 500‐year frequency storms. Cropping systems tested were fallow, conventional tobacco (Nicotiana sp.), mulch‐tilled tobacco, tobacco in grass strips, pangolagrass (Digitaria decumbens), and pangolagrass with all aboveground parts removed. Slopes ranged from 26 to 46%; plots were 10.7 m long. Test areas had been in grass for several years. Final infiltration rates were 3.7, 0.9, and 6.2 cm/hr for Humatas clay, Juncos silty clay, and Pandura sandy loam, respectively. All soils were highly aggregated and remained so throughout all storms. The low infiltration rates of Juncos silty clay are misleading. Actually, most of the rainfall infiltrated this soil but returned as interflow at the lower end of the plots. All soils were quite resistant to erosion due to their high degree of aggregation and in part to the grass grown in previous years. Tillage increased storage capacity in the soil and reduced runoff. All cropping treatments were effective in reducing erosion when compared with fallow, except on Humatas clay, where the fallow treatment permitted the least erosion. Average erosion on all treatments from Humatas, Juncos, and Pandura soils were: Storm 1 — 0.87, 0.51, and 0.06; storm 2 — 5.12, 1.20, and 6.63; and storm 3 — 6.00, 1.72, and 6.69 MT/ha, respectively. Nitrogen, potassium, calcium, magnesium, sulfur, and chlorine in runoff were measured from conventionally tilled tobacco during storm 1. Treated plots received by broadcasting 1,120 kg/ha (2.27 kg/plot) of 12‐6‐16 (N, P2O5, K2O) fertilizer 1 kr before tests began. Concentrations were high at the initiation of runoff and decreased with time as the volume of runoff increased. The average concentration of N ranged from 0.01 to 2.02 ppm, which is well below accepted public health standards. Potassium ranged from 0.01 to 2.29 ppm. Concentrations were highest fox all nutrients in runoff from the fertilized Juncos silty clay plots, because almost all runoff from this soil was actually interflow—infiltrated water that moved through the tilled zone and along the tilled‐untilled interface and then surfaced at the lower end of the plot. Although measured as runoff, no surface flow occurred except at the lower 0.3 to 0.6 m of the plots.
A cropping system is needed in the Southern Piedmont and related areas for increasing production of grain and forage, controlling erosion, and providing a place for safe utilization of poultry litter. No‐till corn (Zea mays L.) production in tall fescue (Festuca arundinacea Schreb.) appears to offer such a system. Corn was notill planted and irrigated in live sod and in sod that was killed with 2.2 and 0.28 kg/ha atrazine and paraquat, respectively. Nitrogen, P, K, and lime applied uniformly to all treatments included 145, 98, 185, and 3,330 kg/ha in 1970 and 145, 138, 323, and 3,330 kg/ha in 1971, respectively. Subplot treatments were 5.6, 11.2, 22.4, and 44.8 metric tons/ha poultry litter, and 335 kg/ha N.Measurements with electrical resistance blocks showed that soilwater content under the corn was never below 50% of the water between field capacity and wilting point. Corn population was higher and yields were better in the killed sod than in live sod both years. Yields in the killed sod were very satisfactory with 9,500 kg/ha (153 bu/acre) from 5.6 metric tons/ha poultry litter plus 145 kg/ha N and 12,960 kg/ha (207 bu/acre) from 480 kg/ha N. Tall fescue present in the live sod after corn harvest was above 2,000 kg/ha in 1970 and above 6,000 kg/ha in 1971. Dead grass plus poultry litter residues after killed sod in 1970 ranged from 6,360 kg/ha with N only to 30,200 kg/ha with 44.8 metric tons/ha poultry litter.Poultry litter provides a vast resource of plant nutrients. No‐till corn in tall fescue with irrigation and poultry litter will produce needed grain, conserve soil and water, and turn a waste product into a resource.
The irrigation requirements for the period May‐August were investigated in relation to some physical properties of Cecil soil as affected by eight cropping systems. These systems ranged from corn grown continuously with stalks removed to sod continuously. The cropping systems had no effect on particle size distribution and total porosity, but crust strength decreased and aggregate stability and infiltration rates increased as the quantity of plant material returned to the soil was increased. The increased water intake was offset by increased deep drainage from the root zone, so there was no change in subsequent irrigation requirements
Evapotranspiration affects the irrigation requirements of crops, and a simple method is needed for determining ET. The evapotranspiration equivalent of solar radiation (RS) is easily computed from data readily available from the U.S. Weather Bureau. The ET/RS ratio for cotton irrigated at Watkinsville, Georgia, showed that Rs data can be used to predict irrigation needs when the ET/RS ratio, daily rainfall, and available water capacity of the soil are known.
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