Increasing Plant Density to Increase Dry Matter in Corn Silage

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Curious corn silage producers continue to ask if raising plant density will increase dry matter (DM) yield of silage crops. And when you increase plant density, what inputs are required to meet the nutrition needs of the field?

Corn for silage is the most important energy crop for dairy and beef cattle rations, with energy-value ranges from 0.5 to 0.7 Mcal per pound DM. Typically, corn plant densities for silage range between 30,000 and 35,000 plants per acre. The following three questions should be addressed when planning to increase corn plant density.

1. What is the economically maximum corn plant density for silage?

Regardless of the crop, farmers continually evaluate how much extra yield can be attained per inch of water or pound of nitrogen. With corn silage production, seeding rate is another factor that farmers often examine for potential yield increases. Typical recommended plant densities for corn silage range from 30,000 to 35,000 plants per acre. With these plant densities, a reasonable DM yield is about 8.0 to 10.0 tons per acre under adequate irrigation.

Research in New Mexico was conducted in 2007 and 2008 to assess the effects of seeding rate and nitrogen rate on corn and sorghum silage grown under limited irrigation. This work showed that there was no difference in DM yield among 22,500, 27,000 and 30,000 plants per acre when corn was irrigated with 20 inches of water. Dry matter yields were maintained at over 10.5 tons per acre and wet yields exceeded 25.0 tons per acre, even at 22,500 plants per acre. This research is important because as irrigation well capacities diminish in New Mexico, growers will have to begin reducing other inputs such as plant populations to remain productive and profitable.

In Wisconsin, Cusicanqui and Lauer conducted a study to assess the effect of plant density and corn hybrid on forage yield and nutritive value. Corn plant densities ranged from 18,000 to 42,300 plants per acre. They found a maximum DM yield at around 35,000 plants per acre and declining DM yield at greater plant densities. They also mentioned that the different corn hybrids responded similarly to plant density.

In a separate study, Cox and Cherney assessed corn DM yield at two plant densities, 32,000 and 47,000 plants per acre. In this study, increasing plant density increased DM yield, but the difference in DM yield between the two plant densities was only 3.7%. The question growers must answer is, “Will the increase in DM yield pay for the 10,000 to 15,000 extra seeds per acre?”

2. Do corn hybrids respond differently to high plant density?

Several studies have been conducted in multiple locations assessing the effect of plant density on different corn hybrids. Overall, there were no differences among corn hybrids under plant density treatments. Aside from rare exceptions, corn hybrids for grain or silage respond similarly to plant density.

3. Do I need to apply more nitrogen (N)?

The study conducted in New Mexico also investigated the effect of nitrogen rate on yield and nutritive value when combined with three seeding rates. Findings indicate that there is no yield difference or change in forage quality among any of the seeding rates when grown with either 195 or 250 pounds of nitrogen per acre when seasonal-applied irrigation was 20 inches or less. Cutting nitrogen by 20% had no negative effect on yield or nutritive value. Future studies in New Mexico will evaluate even lower plant populations and nitrogen rates.

Cox and Cherney evaluated corn silage DM yield and nutritive value at two plant densities (32,400 and 47,000 plants per acre) and six nitrogen rates (from 0 to 223 pounds of nitrogen per acre). Maximum corn DM yield (8.5 tons per acre) was found at 134 pounds of nitrogen per acre, regardless of plant density. There was no response in DM yield above this nitrogen rate. Moreover, corn silage nutritive value did not change above this nitrogen rate. They concluded that corn silage should be produced at 32,400 plants per acre and 134 pounds of nitrogen per acre to combine yield and nutritive value.

Shapiro and Wortmann also conducted a study to assess the effect of nitrogen rate, row spacing and plant density on grain and DM yield. They found the greatest DM yield at 134 pounds of nitrogen per acre, but the optimum grain yield was between 178 and 214 pounds of nitrogen per acre.

Click here to read more about nutritive value, modifying row spacing and water usage with high density corn.

Original article written by Francisco E. Contreras-Govea, Mark Marsalis and Leonard Lauriault with the College of Agricultural, Consumer and Environmental Sciences at the New Mexico State University.

 

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