Paul J. Jasa

Tillage, Residue and Erosion on Moderately Sloping Soils

ABSTRACT TILLAGE treatments leaving 20% or more of the soil surface covered with residue reduced soil erosion by at least 50% of that which occurred from a moldboard plow system. No-till had the least erosion and tended to have the lowest cumulative runoff. These results were based on rainfall simulation tests on six tillage treatments used on both 5 and 10% slopes in continuous corn production.

Soil Erosion from Tillage Systems Used in Soybean and Corn Residues

ABSTRACT RAINFALL simulation techniques were used to compare soil losses from various tillage systems used on plots where corn and soybeans had been grown the previous season. The two year study was conducted on a silty clay loam soil with a 5% slope and on a silt loam soil with a 10% slope. Five tillage treatments, ranging from a moldboard plow system to no-till, were evaluated for each residue at each site. Tillage and planting operations were conducted up-and-down hill on replicated plots. Total soil loss following 63.5 mm of rainfall applied during a 60 min period averaged more than 40% greater from the soybean residue plots than from the corn residue plots for equivalent tillage treatments on the 5% slope. For the 10% slope, the soil loss ranged from 50% to about 12 times greater for the soybean residue. Equivalent tillage treatments in soybean residue had about 40% less surface cover relative to corn residue, which contributed to the difference in soil erosion. Relationships between residue cover and soil loss showed that a 20% cover of either soybean or corn residue generally reduced soil loss by at least 50% of that which occurred from cleanly-tilled soils. Several tillage systems left more than a 20% cover in corn residue. Only no-till consistently left more than a 20% residue cover following soybeans..

ANALYSIS OF TRAFFIC PATTERNS AND YIELD MONITOR DATA FOR FIELD EFFICIENCY DETERMINATION

Field efficiency is an important criterion for determining the expected field capacity and, indirectly, for making important machinery management decisions. The data gathered with a yield monitor during harvest and a DGPS monitor during planting were used to provide time–motion studies of equipment and operator productivity. This study used spatial data gathered by a farmer to determine field performance of a combine and a planter. Five fields were used to compare results from soybean and corn production. Fields that are relatively flat with straight rows were contrasted with contoured fields with slopes up to 3 to 5%. Field efficiency, travel speeds, and unproductive time lapses were compared. When contour patterns were compared with the straight rows, field efficiency dropped on the contours by 10 and 20% for planting and harvesting, respectively. Average travel speeds were slower for contour patterns than straight rows by more than 1.6 km/h (1 mph). Although the histograms of the time lapses were very similar for contour and straight patterns, almost twice the number of time lapses was found with the contour pattern.

FIELD EFFICIENCY DETERMINATION USING TRAFFIC PATTERN INDICES

Field efficiency is an important criterion for determining field capacity during field operations and, indirectly, for making important machinery management decisions. Geographic location data gathered with a yield monitor during harvest and a data logger during planting were used to provide time-motion studies of equipment and operator productivity. This study used these spatial and temporal data to quantify field performance of a combine and a planter. Seven Nebraska fields were used to compare results from soybean and corn production systems. Fields that were relatively flat with straight rows were contrasted with contoured fields with slopes of 3% to 5%. Two unique traffic patterns in fields with a center pivot were compared. Four traffic pattern indices were developed and averaged across each field to indicate the steering behavior (or adjustments) made during field operations. Geo-referenced data were used to predict field efficiency for various traffic patterns. Of the four indices compared, the average steering angle (.) and its standard deviation had the strongest association with field efficiency with Pearson correlation coefficients of -0.654 and -0.664, respectively. The average steering angle for contoured traffic patterns were two to four times in magnitude that of straight- and gently curved-row traffic patterns. The steering angle index gave valuable information about field operating conditions but differences in data recording methods and operational characteristics imposed limitations on statistically appropriate comparison analyses.

YIELD MONITOR ACCURACY: SUCCESSFUL FARMING MAGAZINE CASE STUDY

A joint project of the University of Nebraska and Successful Farming magazine observed the harvest operations of three corn farmers using yield–monitoring technology. Two farmers with level fields of high–yielding corn were asked to operate their combines at under–capacity (20–30% reduction in travel speed), over–capacity (20–30% increase in travel speed), and their typical travel speed. The other farmer was observed going up and down a 5–10% slope. The weight of harvested corn measured by the yield monitor was compared to a weigh wagon after each pass. The results showed that yield monitor calibration and combine operational characteristics play an important role in accurate yield monitor response.

Soil Erosion from Tillage and Planting SystemsUsed in Soybean Residue:Part II - Influences of Row Direction

A rainfall simulator was used to compare soil losses from various tillage and planting systems used in residue from soybeans which had been grown in both wide and narrow spaced rows the previous season. Upand-down hill tillage and planting treatments ranging from a double disk system to no-till planting were evaluated using replicated plots on a silt loam soil in the Nora Series having a 10% slope. Tillage and planting systems used in soybean residue from narrow spaced rows had soil erosion and soil erosion rates that were reduced by approximately SO% compared to the same systems used in residue from wide spaced soybeans. However, the reductions were significant only for the double disk tillage system. There was a trend for the start of runoff to be delayed and for residue cover, accumulated runoff, runoff rate, and sediment concentration to be reduced for tillage systems used in narrow row soybean residue compared to the same systems used in residue from wide spaced rows.

Tillage Factors Affecting Corn Seed Spacing

ABSTRACT AN on-farm survey was conducted in Nebraska to determine factors affecting corn seed spacing unifor-mity. Statistical analysis indicated that relative surface roughness, amount of residue present, amount of preplant tillage, and tillage system were important fac-tors affecting uiformity. Subsequently, replicated tillage plots at eight locations were used to evaluate seed spac-ing uniformity with different planters and tillage systems. Seed spacing coefficient of variation and a planter index developed showed conservation tillage does not significantly reduce seed spacing uniformity.

Tillage Influences on Erosion During Furrow Irrigation

ABSTRACT EROSION and runoff from furrow irrigation of corn was measured for three conventional and three reduced tillage systems in 1981 and 1982. The plots were located on a Hastings silt loam soil having a 0.5% slope and a 366 m furrow length. Erosion was the least for slot-planting and greatest for the chisel system, ranging from 20 to 340 kg/ha, respectively, for the first 45 min of runoff during the first irrigation. Erosion from the fourth irrigation was about 75% less than from the first irrigation. Cumulative runoff after 45 min of runoff was similar for all treatments. Nutrient losses were minimal for all irrigations monitored. For most tillage treatments, no differences were measured between non-wheel and wheel track furrows for cumulative soil loss, erosion rate, sediment concentration, runoff amount and runoff rate.

Tillage And Planting System, Stalk Chopper, And Knife Applicator Influences On Corn Residue Cover

Percent corn (Zea mays L.) residue cover remaining on the soil surface after planting was measured for 11 tillage and planting systems that included combinations of the use, and timing, of a stalk chopper and/or a knife-type fertilizer applicator. Tillage, as well as use of a stalk chopper or knife applicator, significantly reduced residue cover. Only 27 of the 69 stalk chopper/knife applicator/tillage and planting system treatment combinations that were evaluated could be classified as conservation tillage by having at least 30% residue cover remaining after planting.

Subsoiling, Contouring, and Tillage Effects on Erosion and Runoff

A study to evaluate the effectiveness of subsoiling on reducing soil erosion and water runoff from continuous corn production was conducted. A rotating boom rainfall simulator was used on replicated treatments having either preplant in-row subsoiling or postplant between-row subsoiling used in both tilled and untilled surface conditions. Tilled and untilled treatments without subsoiling were used as checks. These six treatments were used up-and-downhill and on the contour.