How crowding affects animals is something I learned about before acquiring a knowledge of how excessive population affects plants. Most of us are quite familiar with the adverse effects of overcrowding on livestock. But it may be difficult to compare too many hoofed animals crammed into too small a space to plant overpopulations.
Comparing certain fish to crops is quite a bit easier. Tilapia were originally farmed in their native Africa. Fast-growing, tolerant of stocking density and adaptable, tilapia have been introduced to many venues to be farmed extensively. Most folks are more familiar with goldfish than they are with tilapia.
Folks raising goldfish in an indoor aquarium observe that the fish they purchased at two inches long might grow up to three inches long. Those same fish turned loose in a small backyard pond will likely grow to be a foot long. If they escape into a much larger habitat (like a lake), we usually call them carp. In that much less confining habitat, they typically grow to two feet in length, weighing up to eight pounds – although carp occasionally weigh in the 30- to 40-pound range.
The size of the environment of a goldfish has everything to do with how much it can grow. To some extent how big that habitat is has a lot to do with how many carp can survive there.
Let’s return to tilapia. These fish were raised at the Milford (NY) vocational school, where I advised the ag program a dozen-plus years ago. Tilapia addressed the restrictive environment by limiting their body size. A mass of water that might have enough room and nutrition to support 100 big fish could support 200 smaller fish. Tilapia are vegetarians, so big tilapia doesn’t eat little ones. Game fish, like pike and bass, approach the crowding issue a little differently – big ones do eat little ones.
Now I’ll try to compare the versatility of these fish to the adaptability of corn, sorghum and sudangrass. These plants are all in the C-4 grouping. Without going into great depth, as I have in the recent past, let’s note that C-4s use plant building block modules consisting of four carbons. What’s so special about this trait is that it enables C-4 group members to acquire and utilize carbon dioxide and water more efficiently than plants that are not C-4s.
Over the last half century, growers have quietly been convinced by seed marketers of the need to plant higher numbers of seeds of sorghum, sudangrass, their hybrids and corn.
But allow me to flash back to my days as a CCE agronomy agent in the 1970s. A variety called Cornell110 was a much better than average corn hybrid; its 80,000 units did a good job planting three acres; 36-inch row spacing was popular; 90% “germ” meant a final stand population of about 24,000. We agents were told that if half of that population was lost but that the remaining stand was uniform 12,000 seedlings, there was no need to replant. The surviving plants “ate” the nutrients which their fallen buddies no longer could.
I remember a case in the ‘70s when an Otsego County dairyman called me out as his Extension agent to examine a piece of corn with major problems. He had planted it early and then it got frosted. He thought it was killed, so he replanted. Only the first planting actually managed to survive. What I was examining was roughly a 60,000/acre population, which was very yellow. The super crowding meant that there wasn’t enough nutrition for all the seedlings.
Additionally, the original population fought the later plants through a behavioral trait called allelopathy. Allelopathy is a biological phenomenon where one plant inhibits the growth of another using its own perfectly natural biochemicals – similar to what game fish do to lesser comrades.
What the farmer ended up harvesting was about three-quarters the normal whole plant dry matter per acre that was poorly eared. Had he called me before he replanted, I would have been able to determine that the seedlings’ growth points were still slightly below the soil’s surface, thus fairly protected from frost – despite the fact that the first true leaves were quite withered. Thus, the grower would not have had to replant.
Here I’d like to tap into the wisdom of Wisconsin crop advisor and seed corn expert Daniel Olson. Olson oversees a crop consulting firm called Forage Innovations. He does sell seed, but he tries not to sell growers more seed than they need. He writes about a physical corn trait called “maximum ear flex.” It is a necessary quality for BTBMR (better than brown midrib) to provide the bushels of corn equal to or greater than the higher planting populations. Often, two equal ears per stalk occur. Many hybrids have ear flex, but they must also exhibit an adequate stalk expansion to create both the yield and the digestibility enhancement.
The principle is when the stalk expands, the lignin (only in the outer rind) becomes a lower percentage of the neutral detergent fiber (NDF). Simultaneously, the highly digestible center – mostly hemicellulose, cellulose and sugar – becomes a greater percentage of the plant. This is analogous to silo diameters. As a silo gets a wider diameter, the silage capacity increases in a non-linear fashion.
When lignin (really the uNDF240, the portion of feed remaining undigested after 240 hours) is reduced as a percentage of the NDF, digestibility (NDFD30) increases. (That’s the portion of NDF digested after 30 hours.)
The punchline to the joke here, according to Olson, is that with BTBMR the kernel numbers of seed corn that used to plant three acres of non-BTBMR corn now plants four acres. This good news for producers also applies to sorghum, sudangrass and their hybrids. Seed sales reps may not consider it good news, because this management approach tends to reduce seed sales.
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