Document Type

Thesis - University Access Only

Award Date

2012

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Howard Woodard

Abstract

Nutrient availability and soil-test levels can differ among tillage systems and can interact with the amount and type of crop residue present. The objectives of this long-term study were to determine the effects no-till and conventional tillage with or without residue removal within different crop rotations on the amount of cumulative phosphorus (P), potassium (K), and zinc (Zn) removed, how cumulative nutrient removal affected soiltest phosphorus (STP), soil-test potassium (STK), and soil-test zinc levels (STZn), and determine P, K, and Zn drawdown ratios. The study was conducted north of Brookings, South Dakota on the "Old Larsen Farm" (44° 20' 5.0202" N 96° 47' 23.1684" W) starting in the Fall of 1999. The major soil type at this site is the Divide loam (fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid, Aerie Calciaquolls) with O to 2 percent slope. The plot design is a strip-split-split randomized complete block with four replications. The dimensions of each plot were 9 m by 9 m. Crop rotations included a com (Zea mays L.)-soybean (Glycine max L.)-spring wheat (Triticum aestivum L.) (C-SW), com-soybean (C-S), and soybean-spring wheat (S-W) and were established in the Spring of 2000. Four treatments were established with in each crop rotation, no-till with residue removed (NT-RR), no-till with residue maintained (NT-RM), conventional till with residue removed (CT-RR), and conventional till with residue maintained (CT-RM). Grain was harvested every year from a 12 m2 sub-plot and a sub-sample was collected for nutrient analysis. Above-ground crop residue was collected from the 12 m2 sub-plot, weighed, and a sub-sample was collected for nutrient analysis. The above-ground crop biomass was placed back onto the plots and spread evenly over the area of removal for the residue maintained plots. The remaining above-ground crop biomass was raked and removed from the residue removed plots. The conventional tilled plots were tilled each fall and again in the spring before planting. Soil samples from 0-15 cm were collected from each plot every other year beginning in the Fall of 1999. Grain, residue, and soil samples were analyzed for phosphorus, potassium, and zinc content. Data was collected and analyzed for this study from 2004-2011. The C-S rotation removed the most P2Os, K2 O, and Zn while the S-W rotation removed the least amount of P2O 5 and Zn. The C-S rotation removed an average of 498 kg P2 O5 ha- 1 , 702 kg K2 O ha- 1 , and 1.185 kg Zn ha- 1 while the S-W rotation removed an average of 366 kg P2O 5 ha- 1 , 548 kg K2O ha- 1 , and 0.856 kg Zn ha- 1 . Removing above-ground crop biomass removed more P 2O5, K2O, and Zn while returning crop residue removed less P2O5, K2O, and Zn. The removal of aboveground crop biomass removed an average of 471 kg P20s ha- 1 , 818 kg K2O ha-I, and 1.204 kg Zn ha- 1 while maintaining above-ground crop biomass removed an average of 394 kg P2 O 5 ha- 1 , 410 kg K2 O ha-I, and 0.904 kg Zn ha- 1 . Tillage had little impact on the amount of P2O5 , K2O, and Zn removed. The use of NT removed an average of 434 kg P2O 5 ha- 1 , 611 kg K2O ha- 1 , and 1.084 kg Zn ha- 1 while the use of CT removed an average of 431 kg P2O 5 ha- 1 , 617 kg K2O ha- 1 , and 1.023 kg Zn ha- 1 . These results suggest that com removes more P2O 5, K2O, and Zn than soybean and spring wheat. Removing crop residues also increases the amount of P2O 5, K2O, and Zn removed compared to leaving crop residues in the field. Soil-test P levels decreased during the course of this study from an average of 40 μg g- 1 to 26 μg g- 1 • Removal of P2O 5 was calculated to be 36.58 kg P 2Os ha- 1 year-• in order to decrease extractable Olsen-orthophosphate STP by 1 μg g- 1 . Soil-test K levels increased from an average of 326 μg g- 1 to 363 μg g- 1 during the course of this stidy. Soil-test Zn levels increased from an average of2.40 μg t 1 to 2.46 μg g- 1 during the course of this study. Potassium and Zn removal requirements to change soil-test levels could not be calculated since STK and STZn levels did not decrease overall during this study.

Library of Congress Subject Headings

Soil -- Testing
Tillage
Crop residue management
Crop rotation
Soils -- Phosphorus content
Soils -- Potassium content
Soils -- Zinc content

Publisher

South Dakota State University

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