Cooperative Extension brought you bmr sorghum-Sudan (and as some claim, fire, flood, and plague of locusts) in the spring of 2000 season. For many it was a new crop, an oddity that was interesting to watch, but will never replace corn. Many watched the research we conducted at the Cornell Valatie Research farm with the help of Cornell Crop and Soils Department, Wolf River Seeds, Carovail Fertilizer and Hollyrock farm.
Then came the summer (or lack of it) of 2000. We reached the beginning of July and farms had 0 to 60% of their normal corn acreage planted. Many turned to the crop in desperation. How did they fare, and what did we learn from research and farm experience.
The year 2000 crop experience:
Yields ran from 0 to 29 tons/acre. The 0 occurred in fields that were planted and then hammered the next day with tremendous rains washing away the seed and fertilizer. The 29 tons of 35% dry matter material was on my research plots that had multiple applications of nitrogen and was allowed to grow until mature seed stage. At this point the crop was over 9 feet tall and lodged at three feet tall (the height of fiber in the stalk). This is not recommended, but was simply a part of the test. (My role is as a professional screw-up. I make the mistakes so you can be forewarned as to not repeat them). Numerous farms that planted the beginning of July achieved yields of 12 to 15 tons/acre by the end of September. Fields hit worse by the wet weather had yields in the 4 to 7 ton of 35% dry matter material.
Feed quality ran as wide a gamut. Tests were from 24% crude protein down to 7%. Energy values (in-vitro) were from .84 to .37. Some farms feeding bmr sorghum-Sudan had a drop in milk when they switched back to corn silage. Others were not so fortunate. Comments such as "This is an efficient feed, we just take it out of the silo and put it in the manure spreader." Others were less kind, "Do we put it in the front of the cow or in the back?" The bottom line is that bmr sorghum-Sudan is like the mother goose nursery rhyme, "when it was good it was very, very good, when it was bad it was horrid. Because so little is know about managing this crop for high producing milk cows, we didn’t bat 100 % on management recommendations. We now have data to dramatically increase the odds of consistently producing a forage better than corn.
Yield
As mentioned above, the first step in achieving high yield is to get a successful stand. Most planted 50 to 60 lbs./acre. With broadcast type planting it appears that the higher side of seeding rate is needed for an adequate stand. Drills and cultipacker type seeders did an excellent job. Air seeding also was very successful as long as the roller had relatively flat roller ridges. Those with 3 inch or deeper grooves on their rolls, buried the seed and the stand was lost. Crops were planted from early May through the end of July. Stands planted in the month of May were severely compromised because all sorghum-Sudan prefers warm soils (was it ever warm this past summer?) Soils at the four-inch depth were 64 degrees at the beginning of May and 52 degrees at the end of May! June plantings, in spite of the record cold and wet month, did well for emergence. As you can see in graph #1, for any planting date after June 1, bmr sorghum-Sudan with sufficient nitrogen beat corn silage. In fact, with additional top dressed nitrogen to replace that, which was lost by the tremendous leaching, the July 15 planting produced yields as high as the NY normal corn silage averages. Unfortunately, farmer experience was less than this.
What we learned is that nitrogen plays a KEY role in producing profitable yields. As you can see in graph #2, as the nitrogen increased, so did the yields. These yields are only 2/3 the potential yield, because insufficient nitrogen was applied and this, combined with the leaching, reduced the total yield. As you can see in the planting date graph, yield potential is actually much higher.
With high nitrogen prices this year, will it price us out of growing the crop? Nitrogen from urea will cost around $0.31 per pound of nitrogen. If only commercial nitrogen is purchased (no manure) to produce a yield of 21-tons of 15% protein crop, it will cost about $0.17 per pound of protein (entire growing and harvesting cost plus the additional nitrogen). To buy this same protein from soybean meal, will cost $0.23 per pound of protein. Thus you can take a 35% yield reduction (13.7 ton/acre) in the bmr sorghum-Sudan and still be break even with the cost of soybean as a protein replacement.
Will we have a year as bad as this for nitrogen loss? Who knows. We did learn two things. First, applying all the nitrogen at planting time is not a good move (unless it is slow release manure nitrogen). By applying only what is needed to grow the next cutting, you can adjust for weather and yield potential in mid season. This also gave us VERY HIGH (85%) percent recovery of the applied nitrogen, in spite of the bad weather. Second, we learned that this multiple application ability is a clear advantage over corn silage. When corn is 3 feet tall and runs out of nitrogen due to the weather, you are basically stuck with much less than potential yield for the season. With bmr sorghum-Sudan, you simply harvest the crop and then apply the nitrogen to grow the next cutting.
Quality
Yields were about what could be expected, given the conditions (but less than what many farms wanted). Quality was a BIG disappointment. There were two main reasons for this.
The first reason is that the wet weather of September made it impossible to properly dry the crop to a level necessary for good fermentation. Wet silage needs to use more sugars than normal before the pH is low enough for proper fermentation. Wet silage also tends to have acetic rather than lactic fermentation. Acetic is only 1/10 as strong as lactic and so much more sugar is used to complete fermentation. Corn silage is composed of two parts. The first is the digestible sugars in the forage. The second is the starch and sugars in the grain. The sugars are used for fermentation. This is one of the reasons why cows milk poorly on wet corn silage. The stalk has lost most of its digestibility, and the residual is in the grain. Bmr sorghum-Sudan is managed with no grain. The entire digestibility is in the forage portion. Wet sorghum-Sudan will continue to ferment until nearly all the energy in the highly digestible stalk is used. The majority of samples that were less than 23% dry matter came back with only half of their normal Nel. The energy had been lost in the inefficient fermentation of silage that was to wet.
The second factor that reduced quality was our effort to get as much yield in as short a time as possible. The majority of the forage was planted in early July and not harvested until the end of September in order to maximize the dry matter yield. At this point it was 5 to 6 feet tall. Unbeknown to us, this came at a tremendous cost in forge quality. Crude protein on the first cut dropped from 17% to less than 10%. This was accentuated by the nitrogen losses that were occurring at the same time. Energy levels, where there was more nitrogen than what the weather left in many farm fields, still dropped from good corn silage levels of .72, down to a good haylage levels of .60 (before it was lost by the above poor fermentation of wet silage). As you can see in graph #3 , all the quality components drop dramatically as the crop grows over 4 feet tall. As you can see in graph #4, even the dry matter accumulation slows down as you get taller than 4 feet. Our conjecture is that the upper leaves shade lower leaves. This latter may be the key reason why the quality drops as lower leaves live off of the photosynthesis of the upper leaves that have sunlight.
Our conclusion on harvesting is that it needs to be cut BEFORE it reaches 4 feet tall for forage quality that will beat corn silage in protein and digestibility, and equal it in energy. Our first take on this is that it appears to reach this stage at 40 days. At this point, you will have 2 to 3 tons of dry matter/acre (5.7 – 8.5 tons of 35% DM). The clear advantage in addition to improved feed quality is that you have only 1/3 to ˝ the amount of water to remove in order to get it to the proper level for fermentation that saves the feed value.
The Bottom Line for the 2001 season:
For those willing to look past the horrible weather and mistakes of last year, and try this new, high quality forage, our recommendation is as follows: Harvest every 40 days (or about 40 inches tall) and apply 100 lbs of available nitrogen immediately after. This should enable you to hit the target of 18 – 20 tons/acre of a forage testing 15% protein and .72 Nel.