Effect of plant growth regulator, Palisade 2EC, and different nitrogen rates on wheat growth and yield

Winter wheat is an important crop in Kentucky and an essential staple to the world’s diet. Continual wheat yield increases are needed to maintain profitable economic returns and to provide adequate grain supplies to feed the ever increasing global population. To increase wheat yields in Kentucky, producers are interested in considering inputs that are logistically feasible and result in profitable returns. One recent product that was labeled for winter wheat in 2012 is a plant growth regulator, Palisade 2EC®, marketed by Syngenta®. Palisade 2EC® has been reported to increase stem thickness and diameter and reduce plant height, thereby reducing plant lodging and yield losses (http://www.syngentacropprotection.com/news_releases/news.aspx?id=163919). Research completed by Syngenta also indicates that grain yield can be increased when Palisade 2EC® is used (Syngenta representative, personal communication). Independent research completed at Michigan State University also found a yield increase of 7 to 12 bu/A when Palisade 2EC® was used, mainly as a function of reduced lodging (Nagelkirk, 2012). Nagelkirk (2012) found that the peduncle length was shorter and peduncle diameter was wider for wheat plants after Palisade 2EC® was applied. In Kentucky, wheat lodging is typically not a widespread problem when good agronomic practices are followed. However, there is significant interest in Palisade 2EC® throughout the Commonwealth. The main questions being asked are: Do increased nitrogen rates increase wheat yields? Can plant growth regulators (PGR) reduce plant height and lodging and increase yields in high nitrogen production systems? Would a high nitrogen/PGR production system be profitable? In 2013, a preliminary replicated trial to examine the effect of Palisade 2EC® at five nitrogen rates (0, 50, 100, 150, 200 lb N/A) and three wheat varieties (Pioneer Brand 25R32, Pembroke 2014, Truman) was established at the University of Kentucky Research and Education Center, Princeton, KY. Four replications of small research plots (4 ft x 10 ft) were established. Palisade 2EC® (5 oz/A) and nitrogen was applied at Feekes 5. Six random plants per plot were harvested May 21, 2014. Internodal lengths were measured for all internodes and peduncle length was measured (Figure 1). Diameter for each internode and the peduncle was measured in the middle of each internode or peduncle. Internode 1 Internode 2 Internode 3 Peduncle Figure 1. Diagram of internode and peduncle lengths. Knott, Ritchey, Van Sanford 2014 KySGGA 2 of 6 Six mature wheat heads were harvested per plot (June 19, 2014) and the number of spikelets per head were measured (Figure 2). The number of seed per spikelet and seed weight will be measured. Plant height was measured June 19, 2014. Wheat plots were harvested June 25, 2014; yield and test weights were measured. Data were analyzed as a split-split plot design using PROC MIXED in SAS (version 9.3; SAS Institute, 2002). In the preliminary trial, mean plant height for all three varieties at harvest was shorter for wheat treated with Palisade 2EC® than for the untreated control (UTC) when N rates were 0 and 50 lb N/A (Table 1). When N rates were at recommended (100 lb N/A) or high rates (150 and 200 lb N/A) statistical differences were not detected. It was surprising that Palisade 2EC® did not reduce plant height at all N rates given the numerous reports in other states that it consistently reduced plant height. In 2014, a variety of unusual weather events occurred. Delayed wheat planting, extremely cold temperatures, and prolonged cold temperatures in the winter and spring may have reduced overall wheat height in 2014. Plant height for the three varieties used in this study was obtained from the University of Kentucky Small Grain Variety Testing Program (http://www.uky.edu/Ag/wheatvarietytest/) from 2011- 2013. When plant height of each of the varieties was compared to previous years and 2014, height was always shorter in 2014 than previous years (Table 2). In 2014, the length of the peduncle for all varieties was shorter when treated with Palisade 2EC® for all N rates except 200 lb N/A (Table 3). The intermodal lengths did not differ (data not shown). For internode diameter, internodes 2 and 3 diameters at 200 lb N/A were larger when Palisade 2EC® was applied (Table 4). The only consistent findings were that the diameter of all internodes and the peduncle were smaller when Palisade 2EC® was applied to wheat that did not receive any additional nitrogen (0 lb N/A). For number of spikelets per head, both Pembroke 2014 and Truman had more spikelets per head after Palisade 2EC® was applied than for the untreated control (UTC; Table 5). In both cases, the increase was less than one spikelet per head. Yield, test weight, number of seed per head, and seed weight data has not yet been analyzed. It will be very interesting to determine whether yield differs exist between the wheat treated with Palisade 2EC® and the UTC and if specific reasons for yield differences, if detected, can be determined based upon the data collected. Although considerable data was collected in 2014 for differences between wheat when Palisade 2EC® was applied and an UTC at five N rates, 2014 was an unusual year. The wheat crop in 2014 was shorter than normal. This likely also reduced lodging. In fact, in early June 2014 wheat in this study began to lean over, but within 3 days there was no detected lodging or leaning visible. Ideally, an additional year of investigation at numerous locations is necessary to determine the profitability of Palisade 2EC® in intensive wheat management programs in Kentucky.