Cotton Population and Row Spacing

 

Key Points

 

  • Improvements in seed technology and yield potential in cotton have increased seed costs on the farm. Growers want to know if lower seeding rates can help offset seed costs while maintaining yield potential.

  • Determining seeding rate and row spacing is critical for production efficiency, management, and economic return.

  • Final plant population goals should consider the effects of pest pressure and poor environmental conditions to help prevent additional costs associated with replanting.

 

The Impact of High and Low Plant Populations 

 

Seeding rate and plant population are not the same. Seeding rate is determined by many considerations, including yield goal, management preferences, weather conditions, irrigation, potential plant loss, and desired final plant population. Cotton plant architecture can be determined by final plant populations, with higher plant densities having taller, more upright plants, and lower densities having branchier lateral growth.

High final plant populations require aggressive management and should be used in combination with appropriate variety selection. When cotton plant populations are high, the following can occur:

  • More first position bolls are set, which can lead to increased harvest efficiency with first position bolls maturing first. Fiber quality can be higher because bolls have matured around the same time.1

  • Later initiation of fruiting with a somewhat shortened boll loading period due to running out of time at the end of the season.

  • Decreased drought tolerance.

  • Increased fruit shedding due to difficult-to-control plants from mid to late season.

  • More aggressive plant growth regulator (PGR) use during the growing season.

  • Increased number of small bolls, which can lower harvest efficiency as lint is more difficult to obtain from smaller bolls.1

Cotton plants compensate well in lower plant populations and skips in the field. This ability is limited and comes with its own considerations. Lower plant populations can lead to:

  • Increased plant size. However, larger branches and stems can lower harvest efficiency. 

  • Increased growth of vegetative and fruiting branches and secondary and tertiary boll production. Waiting on these bolls to mature can delay harvest and impact fiber quality due to the variation in lint maturity.1 Low populations require time to accumulate a fruit load that allows for optimal yield. Additional time can add management challenges in late-planted or short-season situations.

  • Shorter plants due to increased lateral branching. This can lead to lower PGR requirements. 

  • Increased boll retention.1

 

Local Considerations

 

Several local conditions can influence the need to adjust cotton seeding rates depending on management system/style, variety characteristics, projected weather patterns, and planting date. Some of these specific conditions include:

Early planting. A challenge of early planting is the ability to establish and maintain an adequate stand in the face of seedling disease, cold weather, and generally difficult establishment conditions. In the case of early planting into adverse conditions, seeding rates should be increased to compensate for potential losses. For more information, read the Spotlight  Optimum Planting Conditions and Seed Placement.

A short growing season. This scenario includes any case where earliness is at a premium. Cotton planted late or in areas with a historically shorter growing season generally fall into this category. In cases where earliness is required, planting higher seeding rates, in combination with aggressive in-crop management and variety selection can help with earliness while maintaining adequate yield potential. Having more plants in the field allows a relatively high level of yield accumulation in shorter periods of time as compared to less dense stands. This ultimately allows for an earlier crop to be harvested.

For more information, read the Spotlight Managing Late-Planted Cotton

Planting on “growthy” soil types. Highly productive soils that have demonstrated the need for aggressive growth control in the past can often benefit from lower seeding rates. Fewer plants generate less competition for resources and thereby usually require less growth control. 

High input, high yield environments. These production environments require the most aggressive decision making, management inputs, and carry somewhat higher risk. In this scenario, desired final plant populations are generally above average for a region. These fields are ideal for cotton production and are very aggressively managed with PGRs, fertility, chemical control, and irrigation applications. These factors influence the outcome of a crop in any field, but in this environment, having relatively high numbers of surviving plants establishes the yield potential early in the season. 

Setting a target final plant population can be accomplished by calculating a target number of plants per acre based on desired seed per foot. Seeding rates vary greatly across the cotton growing area and are based on historical planting conditions that can support or limit stand establishment. It is recommended to plant roughly 20% over the target plant population to account for any minor issues at planting.2 Seeding rates can be adjusted as weather conditions change.

Minimum final plant populations can vary across the cotton growing area. North Carolina State University recommends a minimum of 30,000 plant per acre to maintain yield potential.2 Mississippi State University recommends a minimum of 15,000 plants per acre.4 These minimum populations require optimal growing conditions (high quality seed, warm soil temperatures, positive weather forecast) and even plant distribution throughout the field. Final plant populations that are lower than expected should be assessed to determine if replanting is necessary. For more information on how to assess plant stands and how to manage lower than expected stands, read the Spotlight (4016_S1/140602060424Cotton Replant Decisions.

 

Row Spacing

Table 1. Seed drop rates for desired plants per foot of row.

Typical cotton row spacing ranges from 30- to 40-inch rows. Narrower row spacing can lead to earlier canopy closure, increased photosynthesis, and an earlier-maturing crop. When moving production to a narrower row, seeding rate should be decreased. Narrower rows may require more intensive growth and fertility management.3

For additional information about seeding rate and row widths, the following demonstration reports are available:

Response of Deltapine® Cotton Products to Seed Spacing - Coastal East, 2018 Southeast

  • Research report from the Carolinas that evaluates the yield response of Deltapine varieties to seed spacing.

 Row Configurations in Cotton Production,2019 Midsouth  

  • Scott Learning Center research report examining the impacts of wider rows on cotton yield and fiber quality.

 

Sources

1 Adams, C., Santanu, T., and Emi, K. 2018. Determination of a plant population density threshold for optimizing cotton lint yield: A synthesis. Field Crops Research. sciencedirect.com/science/article/

2 Collins, G. 2015. Seeding rates and plant populations. North Carolina State Extension. https://cotton.ces.ncsu.edu/

3 Reinbott, D.L. and Stevens, G. 2019. Cotton tillage and planting guidelines. University of Missouri Extension. G4270. https://extension2.missouri.edu/g4270

4 Dodds, D. 2016. What is an acceptable final plant population in cotton? Mississippi State University Extension. https://www.mississippi-crops.com/2016/06/03/what-is-an-acceptable-final-plant-population-in-cotton-2/.

Web sources verified 02/27/20.

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