Plant Population for Leafi es
How does leaf area translate into yield?
A corn plant’s leaves are the factories that convert sunlight to yield. The chloroplasts within leaf cells produce glucose sugars during photosynthesis. This sugar energy is used for plant growth and development while the plant is young. After the plant reaches fl owering, these sugars are transported to the developing kernels on the ear to become starch. Starch accumulation is fueled primarily by the above ear leaves, which receive the most sunlight once the plant is grown to full height, while the early growth of the plant was achieved by the below ear leaves, which become shaded as the plant grows.
The yield potential of a corn crop is related to its leaf area index, which is the one-sided green leaf area per unit of ground surface area. The leaf area index of a corn crop can be maximized by increasing plant population or by increasing leaf area on a per plant basis.
Grain corn hybrids produce a maximum of 5-7 leaves above the ear, so these hybrids are planted at a high population of 33-36,000 plants per acre (ppa) to maximize their leaf area index. Leafy Corn Silage Hybrid plants have 8-13 leaves above the top ear, so they have an increased leaf area on a per plant basis. Because Leafi es are larger plants, they need more room to produce their intended crop.
To achieve this, they must be planted at a lower population of 28,000-30,000 ppa. Leafy Corn Silage Hybrids have an increased potential over non-Leafy hybrids to produce high starch yields on a per plant basis because of their high leaf area combined with their fl exear type.
Comparing apples to apples
The dominant industry message is to plant all corn hybrids at high populations in order to maximize silage yield. While this advice is well-taken for grain hybrids, it is detrimental to a Leafy Corn Silage crop to plant it at the high populations recommended for grain. Table 1 below takes into account the higher leaf area of a Leafy Corn Silage Hybrid and compares that to the population density of a grain hybrid.
| Leafy planted at | is comparable to | Grain planted at |
|---|---|---|
| 25,000 ppa | x 40% more leaf area | 35,000 ppa |
| 28,000 ppa | x 40% more leaf area | 39,000 ppa |
| 35,000 ppa | x 40% more leaf area | 49,000 ppa |
When leaf area is accounted for, you can see that planting a Leafy Corn Silage Hybrid at 35,000 ppa gives a comparable canopy to the grain hybrid at 49,000 ppa. Planting the Leafy at 28,000 ppa gives the same leaf canopy as the grain hybrid at 39,000. To achieve the equal leaf area canopy as a grain hybrid that is planted at its recommended population of 35,000 ppa, the Leafy would be planted at 25,000 ppa.
Population affects yield
Leafy Corn Silage Hybrids have been bred and tested for the market since 1989. In that time, numerous population studies have been conducted on the best hybrids. They have suff ered hot dry seasons and experienced major weather events with high winds and heavy rains. What has been discovered is that plants with 8-9 LAE achieve maximum yields at 30,000 ppa. For plants with 10-11 LAE, maximum yields result when they are planted at 28,000 ppa. At 28,000 to 30,000 ppa, Leafy Corn Silage Hybrids have strong roots and good drought response. They also produce a crop with excellent feed qualities – high starch and a good proportion of digestible fi ber. At these populations Leafi es are higher-yielding than grain hybrids that are planted at 35,000 ppa by about 10%.
Plant at 30,000 ppa for Leafi es with 8 to 9 leaves above the ear and at 28,000 ppa for 10 to 11 leaves above the ear.
Balancing yield with quality
When we plant a Leafy Corn Silage Hybrid, we are growing FEED that must be digested to produce MILK, so we aim to grow this crop at the population that will produce the highest quantity of dry matter with the highest grain yield and best fi ber digestibility, while achieving the best crop security. In our population studies, we have seen that in average conditions, the YIELD of a 10-11 LAE Leafy will not be diff erent between 28,000 and 32,000 ppa, and will often be less at 36,000. But when we look at the diff erence in the QUALITY of the feed that is produced at diff erent populations, we see that maximum grain yield and digestible fi ber is achieved at the lower 28,000 ppa. For 8-9 LAE Leafy hybrids, this number is 30,000 ppa. Feed quality aff ects milk production potential.
Figure 1 shows the typical stature of a grain hybrid and a Leafy Corn Silage Hybrid. Note the number of leaves above the ear (LAE), the size of these leaves and the position of the ear. The Leafy Corn Silage Hybrid has 10 LAE compared to 6 LAE on the grain plant.
Figure 2 shows the diff erence in leaf area between the two plants. The four leaves highlighted in red just above the ear are the extra leaves on the Leafy Corn Silage Hybrid. This Leafy plant has 70% more leaf area above the ear than the grain hybrid. The ear position on the Leafy is lower than the grain hybrid, so the Leafy has about 40% more total leaf area than the grain hybrid.
Leafy Corn Silage Hybrids have 70% more leaf area above the ear per plant than dual-purpose grain hybrids.
Leafy Corn Silage Hybrids have 40% more total leaf area per plant than dual-purpose grain hybrids.
Balancing yield with quality
When we plant a Leafy Corn Silage Hybrid, we are growing FEED that must be digested to produce MILK, so we aim to grow this crop at the population that will produce the highest quantity of dry matter with the highest grain yield and best fi ber digestibility, while achieving the best crop security. In our population studies, we have seen that in average conditions, the YIELD of a 10-11 LAE Leafy will not be diff erent between 28,000 and 32,000 ppa, and will often be less at 36,000. But when we look at the diff erence in the QUALITY of the feed that is produced at diff erent populations, we see that maximum grain yield and digestible fi ber is achieved at the lower 28,000 ppa. For 8-9 LAE Leafy hybrids, this number is 30,000 ppa. Feed quality aff ects milk production potential.
Figure 3 illustrates the diff erences between the same Leafy Corn Silage Hybrid planted at 28,000 ppa and 35,000 ppa at the same location.
At 28,000 ppa, the hybrid produced large ears and thick stalks. At 35,000 ppa the ear and stalk size declined. As the stalk size declines, so too does its digestibility.
In State Trials where the Milk 2006 formula is used to calculate milk per ton, the Leafy Corn Silage Hybrids show less starch and milk per ton, though they generally still have competitive yield per acre. In our trials we grow dual-purpose hybrids at their recommended population of 35,000 ppa and Leafy Corn Silage Hybrids at their population of 28,000 ppa, in three row plots. We harvest only the center row to get the best comparable data. In these population-sensitive trials, the Leafi es show their undeniable advantage in milk per ton and milk per acre.
Take our well-researched advice: plant your Leafy Corn Silage Hybrid at the population that will produce the largest quantity of high quality feed for milk production – 30,000 ppa for 8 to 9 LAE hybrids and 28,000 ppa for 10 to 11 LAE hybrids – and get the added benefi t of buying less seed. All you need to do is change that planter population setting. When you plant a Leafy Corn Silage Hybrid, less is certainly more.
Hybrid with glassy/mealy grain with seeding density
The part of the core of such plants is larger than the fraction of the outer shell. It increases the proportion of digestible fiber in the diet.
Plants with bigger ears and larger total yield.
Stems cut into the same internode. The core is better absorbed (higher content of neutral-detergent fiber) than the outer shell.
Five samples of the ears of a flexible type from crops with different seeding densities.
Hybrid with glassy/mealy grain and seeding densitie
The part of the core of such plants is larger than the fraction of the outer shell. It increases the proportion of digestible fiber in the diet.
Plants with bigger ears and larger total yield.
