Rainout Shelter: A Tool for Understanding the Link between Soil Water, Irrigation, and Corn Yield

Transcription

1 Monsanto Learning Center at Gonburg, NE Rainout Shelter: A Tool for Understanding Link between Soil Water, Background Several studies have evaluated corn yield response to water applied. However, such field studies have been conducted in open fields with little or no control over environmental factors such as precipitation. The rainout shelter (ROS) provides a unique opportunity to remove precipitation as a variable and to carefully manage water inputs to study soil-water-plant relationship that leads to yield response. A previous corn study in ROS focused on water stress at various growth stages and compared wateruse efficiency of a Genuity DroughtGard Hybrids product against a drought-tolerant check that was not a DroughtGard Hybrids product. The DroughtGard Hybrids product used water more efficiently than check when exposed to drought stress at various growth stages evaluated. The objective of this study was to evaluate corn yield response to water stress and different levels of irrigation. Determining water use efficiency and amount of irrigation required to obtain first bushel of corn grain is still uncertain and greatly depends on product, timing of water application, soil plant-available water, and or environmental conditions. Questions being asked: At what level of irrigation or available water does corn plant produce first bushel of grain per acre? What is water use efficiency at various levels of irrigation? Do products of different relative maturities affect water use and efficiency? Materials and Methods Rainout shelter The ROS is a metal building that moves on rails to enclose plot area when it detects a raindrop (Figure 1). The plot area consists of 36 irrigation zones (individual research plots), each measuring 2 feet in length by feet in width. Each irrigation zone is surrounded by a 6-foot deep soil moisture barrier and individualized drip irrigation system. Agronomics Two Genuity DroughtGard Hybrids of 1 and 111 days relative maturity (RM) were planted on May 24th in 3-inch rows at 21, seeds/acre. Each plot consisted of 4 rows, where only 2 center rows were harvested for data. Plots were harvested on October th. Figure 1. Rainout shelter on September 9, 213. Management Nitrogen fertilizer was hand-applied at a rate of 2 lb/acre lb N/acre (Urea) broadcasted before planting lb N/acre (UAN) side-dressed on July 19th (between V and V16 growth stages) Standard weed management across trial maintained a weedfree environment. Water use treatments Six water use treatments by product were randomly allocated to irrigation zones. Water use treatments were 6, 8,, 12, 18, and 24 inches of water, where each treatment consisted of water applied through irrigation plus plant-available water in soil. The trial was set up in a completely randomized design and replicated three times. The irrigation management throughout growing season depended on treatment. Periodic irrigation events were proportional to treatment applied and somewhat evenly distributed across growth stages (Figure 2). Soil water measurements In order to determine total water used by crop, volumetric water content (inches/foot) was measured at each foot increment down to a depth of 6 feet using a neutron probe moisture meter. Soil water content was monitored before planting, during growing season, and at harvest through a 2 inch diameter aluminum pipe (access tube) installed into soil in each irrigation zone.

2 Monsanto Learning Center at Gonburg, NE Rainout Shelter: A Tool for Understanding Link between Soil Water, 25 VE VE V5 V11 VT R1 R5 V5 V9 V15 R1 R5 Irrigation (inches) 2 15 VE V5 V7 V12 R1 R May 31-May 7-Jun 14-Jun 21-Jun 28-Jun 5-Jul 12-Jul 19-Jul Date 24 inches 18 inches 12 inches inches 8 inches 6 inches Growth stages 24 inches Growth stages inches Growth stages 6 inches Figure 2. Cumulative irrigation for all treatments and growth stages associated with 6,, and 24 inch treatments. 26-Jul 2-Aug 9-Aug 16-Aug 23-Aug 3-Aug 6-Sep 13-Sep 2-Sep 27-Sep Soil water measurements started on June th and ended on October th. The change in available water content was n estimated by depth using final measurement minus initial measurement. Average and marginal water use efficiency (WUE) Average and marginal WUE were calculated using eir water applied through irrigation or estimates of water used by crop. For example: Average WUE used = Yield/water used Marginal WUE used = Yield gain/additional inches of water used Results Irrigation management and growth stages Timing of irrigation played an important role in results obtained (Figure 2). Controlled irrigation allowed corn plants to survive during growing season even in 6 inch treatment. In uncontrolled conditions, erratic distribution of rainfall events would have prevented a corn plant that only received 6 inches of rainfall from completing its development cycle. Despite timely irrigation management, slow rates of vegetative growth were observed as water availability decreased. For example on July 16th, growth stages were V7, V9, and V11 for 6,, and 24 inch treatments, respectively.

3 Monsanto Learning Center at Gonburg, NE Rainout Shelter: A Tool for Understanding Link between Soil Water, 1 Day RM 111 Day RM inches 12 inches inches 12 inches Figure 3. Differences in corn plant growth at each treatment level for both RM on September 9, 213.

4 Monsanto Learning Center at Gonburg, NE Rainout Shelter: A Tool for Understanding Link between Soil Water, Corn yields Corn grain yields progressively increased along with increases in irrigation for both products (Table 1, Figures 4 and 5). Corn was not expected to yield in 6 and 8 inch treatments based on previous knowledge. The 6 inch treatment yielded 59 and 69 bu/ acre on average for 1 and 111 RM products, respectively. The 8 inch treatment yielded 69 and 72 bu/acre on average for 1 and 111 RM products, respectively. Corn yields between products were very similar at each treatment level. The largest differences in yield between products were observed in 6 inch and 18 inch treatments, where 111 RM product yielded and 14 bu/acre more than 1 RM product, respectively. Soil water profiles Soil water distribution in soil profile was different between products (Figures 6-7). For both products, change in plantavailable water (final initial measurement) showed that water was mainly obtained from upper 2 feet of soil profile in 6, 8,, and 12 inch treatments. Additionally, it seems that longer-season product may have obtained water between 3 and 6-ft soil depths mainly at 6 and 8 inch treatments. On or hand, re was water accumulation to a depth of 4 feet under both products in 18 inch treatment. In 24 inch treatment, however, amount of water remaining in soil profile under 1 RM product was larger than under 111 RM product. In treatment using full irrigation, re was a surplus of 2.4 inches of water remaining in soil profile under 1 RM product compared to 111 RM. In or words, for every additional day in RM, corn crop used on average ~.24 inches of water per day. Water use efficiency (WUE) Average WUE used (bu/acre per inch of water used) was variable across treatments, ranging between and 12 for both 1 and 111 RM products (Figure 4). The largest estimates of WUE were observed up to 12 inch treatment and slightly declined at 18 and 24 inch treatments for both products. On or hand, marginal WUE (yield gain per additional inch of water) was largest between 8 to inch and to 12 inch treatments for both products (Table 1). Table 1. Water use treatments, corn yields, and water use efficiency (WUE) for both products. Water WUE Marginal WUE Product Treatment Applied Used Yield Applied Used Applied Used RM inches bu/acre bu/inch/acre

5 Monsanto Learning Center at Gonburg, NE Rainout Shelter: A Tool for Understanding Link between Soil Water, Yield (bu/acre) WUE (bu/acre/inch) Water use treatment (inches) 1 RM 111 RM 1 RM WUE used 111 RM WUE used Figure 4. Corn yields and average water use efficiency (WUE) by products at each treatment level. 1 Day RM 111 Day RM inches 12 inches inches 12 inches Figure 5. Ear sizes by water use treatment and RM on October 9, 213.

6 Monsanto Learning Center at Gonburg, NE Rainout Shelter: A Tool for Understanding Link between Soil Water, Change in available water (inches/ft) Therefore, largest marginal returns will be obtained in se situations. In or words, in a water-limited situation our results suggest that investing up to 12 inches of water will provide highest profitability. Key Messages 1 While grain yields of 59 and 69 bu/acre were obtained with 6 inches of water used, it must be noted that irrigation 2 strategy likely played a more important role in yield formation than total quantity of water used. 3 WUE and marginal WUE were both optimized at 12 inch 4 treatment, and slightly declined for 18 and 24 inch treatments. 5 Corn products of 111 RM used 2.4 inches of water more than 1 RM products as estimated by water left in 6 soil profile. However, estimates of WUE were similar for both products. Legal The information discussed in this report is from a single site, 3 replicate demonstration. This informational piece is designed to report results of this demonstration and is not intended to infer any confirmed trends. Please use this information accordingly. Monsanto Company is a member of Excellence Through Stewardship (ETS). Monsanto products are commercialized in accordance with ETS Product Launch Stewardship Guidance, and in compliance with Monsanto s Policy for Commercialization of Biotechnology-Derived Plant Products in Commodity Crops. This product has been approved for import into key export markets with functioning regulatory systems. Any crop or material produced from this product can only be exported to, or used, processed or sold in countries where all 1 necessary regulatory approvals have been granted. It is a violation of national and international law to move material containing biotech traits across boundaries into nations where import is not permitted. Growers should talk to ir grain handler or product purchaser to confirm ir buying position for this product. Excellence Through Stewardship is a registered trademark of Biotechnology Industry Organization. Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and wear conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. Soil depth (ft) 1 RM Figure 6. Change in available soil water content at each treatment level for 1 RM product. Soil depth (ft) ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. DroughtGard 5 and Genuity are trademarks of Monsanto Technology LLC. Leaf Design is a registered trademark of Monsanto Company. 213 Monsanto Company JMG 6 Change in available water (inches/ft) RM Figure 7. Change in available soil water content at each treatment level for 111 RM product. 24