Conservation tillage and water management are important factors affecting corn yield along with soil health in Fargo clay soil that is high in smectitic clay (48.7%) that makes them poorly drained and sticky in nature. Subsurface drainage helps to remove excess soil moisture and provides opportunity to adopt conservation tillage practices such as strip and no tillage. Minimum tillage helps to maintain and enhance water movement through soil profile and increase the amount of drain flow. Higher disturbances under chisel plough during early spring can result into early nitrogen loss through subsurface drain before crop can use it. Deciding on subsurface drain depth and spacing also influences nutrient loss, closer drain spacing results in fast removal of excess water but also involves increased cost of installation. Wider drain spacing could reduce the cost but also significantly could reduce the corn yield due to prolonged water stress condition. Installation of control structures in subsurface drainage system provide an opportunity to control.
- Estimate the effect of different tillage practices and tile drainage condition on corn yield (Bu/ac).
- Compare corn yield (Bu/ac) under different tile spacing and depth combination.
- Determine the nutrient availability (lb/ac) as influenced by tile drainage and tillage management.
A field trial was conducted for 2017 growing seasons (May to September) at Casselton, North Dakota (46°49’25.03″N, 97°13’5.70″W) on a Fargo silty clay soil (fine, smectitic, frigid typic epiaquerts). The experiment was conducted in Ron Holidays’s farm. Subsurface drain lines were installed in June 2013 and this is fourth growing season over four years. Basic soil properties are presented in Table 1.
Experiment I: Subsurface drainage, rotation and tillage effect on corn production
|Table 1. Basic soil properties of the experimental site|
|NO3-N (lb/ac)-2 feet||19|
For this experiment, we followed strip-split-split design with four replication. Three drainage system (i) no drainage (check-surface drainage only), (ii) conventional drainage (OT), (iii) controlled drainage (CD) are placed as main plot and under each strip two rotation, (1) continuous corn (CC) and (2) corn-soybean (CS) and under each sub plot, three tillage practices, (i) chisel (CH), (ii) strip-till (ST) and (iii) no-till (NT) as sub-sub plot randomized with four replication (Figure 1). Corn are planted every year such that corn is followed by soybean. Controlled structure was set at one feet below soil surface during all growing season in dry period and 3 feet below soil surface at wet period. Three drainage systems are 30 feet apart. Plots are 30 feet long and 11 feet wide with 22-inch row spacing. Statistical analysis for will be based on strip-split design with drainage as main-plot and tillage as sub-plot. We used split plot design for this experiment with four replication for analysis.
Experiment II: Corn production as influenced by subsurface drain depth and spacing
Three strips of corn, soybean and sugarbeet following corn-sugarbeet-soybean. Each strip have four pseudo-replication of six rows. Two tile lines were installed at three tile spacing of 30-, 40-, 50-feet at two depths, 3-feet and 4 feet at each level of tile spacing.
Crop yields and residual soil NO3-N for corn plots were subjected to general linear model analysis of variance PROC GLM. Fixed effects include drainage, rotation and tillage system; whereas, replication, replication × rotation and replication × rotation × drainage were random effects for corn yield analysis. Fisher’s protected least square difference (LSD) at α = 0.05 was used to separate treatment means. All statistics were analyzed using Statistical Analysis System software (SAS, 2013)Statistical Analysis:
In 2017, corn yield was significant for rotation (sub-plot) (P=0.001) and tillage (sub-sub plot) (P=0.002) whereas, drainage (main plot) (P=0.159) had no significant effect. Corn-soybean rotation recorded highest corn yield compared to CC (181.6 Bu/ac). Chisel plow recorded highest corn yield (145.5 Bu/ac)) and the lowest was found with ST (181.9 Bu/ac).
Likewise, in 2017, two-way interaction among drainage, rotation and tillage had significant effect on corn yield. Highest corn yield was observed with conventional drainage under CS (201.1 Bu/ac) and, the lowest was found with conventional drainage under CC rotation (168.1 Bu/ac). The highest corn yield was recorded with CS×CH (14.30 Mg ha-1) and, the lowest was found with CC×ST (211.6 Bu/ac). No drainage with CH recorded highest corn yield of 210.2 Bu/ac, which was 17% higher than lowest yield recorded by no drainage with ST. Likewise, in 2017, two-way interaction among drainage, rotation and tillage had significant effect on corn yield. Highest corn yield was observed with conventional drainage under CS (201.1 Bu/ac) and, the lowest was found with conventional drainage under CC rotation (168.1 Bu/ac). The highest corn yield was recorded with CS×CH (211.6 Bu/ac) and, the lowest was found with CC×ST (177.0 Bu/ac). No drainage with CH recorded highest corn yield of 208.9 Bu/ac, which was 17% higher than lowest yield recorded by no drainage with ST. And, no three way interaction effect was observed in 2017 (P=0.461). In 2017, corn yield was highest with 15 m drain spacing (183.5 Bu/ac), with the lowest yields observed with the 9 m spacing and there was significant impact of drain depth and interaction (depth×spacing).
For first experiment, soil NO3-N content in corn plots significantly responded to rotation (P=0.001) and tillage (P=0.001). In 2017 growing season, CS rotation plots recorded highest residual soil NO3-N (68.49 kg ha-1) and lowest with CC rotation (47.02 kg ha-1). Residual soil NO3-N was highest under CH (91.96 kg ha-1) and lowest with ST (34.90 kg ha-1). No difference in the residual soil NO3-N content was observed in second experiment.
This shows that in Fargo clay soil, installation of subsurface drainage is likely beneficial in wet years only. The decrease in yield gap between no-till and chisel plow over four years shows that conservation tillage will require more time to show positive effects. Continuous corn in poorly drained soil with no-till is not advisable due to low yield and high residual nitrate. These results suggest that subsurface drainage did not improve corn yield due to lower than average rainfall, but interaction between drainage, crop rotation and tillage has significant effect on crop yield. Short-term study of soil water management in Fargo clay soil suggested there is need of detailed and long-term experiment to understand interaction among climate and crop management practices.