Template:Chapters 6.11

6.11 - High Density Sowing for Weed Suppression

Usama Elsaigh, University of Guelph, Canada

Suggested citation for this chapter.

Elsaigh,u. (2022) High Density Sowing for Weed Suppression. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Introduction

High density sowing is a farming technique that involves planting seeds more closely than conventional spacing guidelines (Subedi et al., 2020). This can be done by increasing the seeding rate and/or planting more narrow rows (Province of Manitoba, n.d.). This method maximizes the use of available land, improves crop yield, and assists with the suppression of weed plants. High density sowing can be particularly helpful in poor regions of Africa and South Asia, where smallholder farmers face numerous challenges such as limited access to herbicides, and the high cost of hired manual labour (Gianessi, 2010).

These challenges associated with weed control in developing countries, require women farmers to spend a considerable amount of time removing weeds by hand (Gianessi, 2010). In sub-Saharan Africa, 70% of food production comes from small-scale farms, and hand weeding is the most common method of weed control (Gianessi, 2010). Women contribute to over 90% of the hand weeding, taking up to 30-90 hours per hectare, more than any other field activity (Gianessi, 2010). Despite the significant amount of energy and time invested in weed removal, crop yields are still very low (Lindell, et al., 2022). Women farmers have several responsibilities other than hand weeding the fields. These responsibilities often take away from the time allocated to working in the fields (Gianessi, 2010). This results in inconsistent and inefficient removal of the weed throughout the season, affecting crop yield by 50% (Gianessi, 2010).

Other factors such as shortage of labour and poor weeding materials also contribute to the loss of crop yield (Gianessi, 2010). 80% of small-scale farmers mentioned that they do not fully utilize available farming space due to the challenges associated with weeding (Gianessi, 2010).

High density sowing proves to be an efficient and low-cost alternative to herbicides and mechanical farming tools. Moreover, it is a relatively simple solution to implement to address the challenges associated with weed control on smallholder farms (Martins et al., n.d.).

Benefits of High

High density sowing provides benefits in terms of increasing crop yields as well as aiding in the suppression of weeds (Chikoye et al., 2004). Farmers can adopt high density farming techniques to maximize the use of available farmland and increase yields without the need for more space (World Bank, 2019). This is especially helpful to smallholder farmers because it provides them the opportunity to make a living despite limitations in farming space (World Bank, 2019). High density systems are also proven to be more environmentally friendly (Lindell et al., 2022).

High density planting has a significant effect on crop yield in comparison to low density (Akintoye, Lucas, & Kling, 2008). For example, a study conducted in Burkina Faso on cowpeas showed that in comparison to low density, high density and super high density planting produced the highest yields, an increase of up to 214%, with an average of 88.9% (Ishikawa et al., 2022). However, the best results occurred when both high density systems and increased fertilizers were introduced (Akintoye et al., 2008). Evidence shows that the maize response to high density is heavily dependent on environmental conditions and the initial supply of nitrogen fertilizer. (Akintoye et al., 2008). In perilla sprouts, as the planting density was increased, so did the yield, by up to 33% compared to standard sowing methods (Wu et al., 2020).

High density sowing is an effective method for suppressing weed growth, eliminating the need for herbicides and mechanical weed control tools which are more expensive and difficult to procure (Xi et al, 2022). High density sowing increases the fitness of the crop when competing with weeds for resources such as soil nutrients and sunlight (Ishikawa et al., 2022). There are several advantages without a trade-off in crop yield (Martins et al., n.d.). High density sowing increases the root length which in turn makes it more difficult for weeds to grow and propagate in such a competitive environment. The increase in density of plants allows less light to pass, therefore creating a shaded canopy which is unfavorable for weeds (Xi et al., 2022). These factors contribute to an environment that is unfavorable for weed growth (Xi et al., 2022).

Critical Analysis

High density planting systems are being adopted more frequently around the world. Thus, there needs to be an evaluation of how that affects the risk of disease and pest infestation (Lindell et al., 2022). High density sowing has been shown to decrease the risk of disease and pest infestation in certain crops (Martins et al., n.d.), while increasing the risk in others (Lindell et al., 2022). Typically, the increase in density alters the microclimate of the crop which is a major factor in the natural management of bacterial and pest infestations (Lindell et al., 2022). This is determined by factors such as airflow, light penetration, and humidity (Lindell et al., 2022). The high foliage contributes to high humidity, less airflow, and decreased light penetration, which are all factors conducive to pests and bacterial infestation (Lindell et al., 2022). For example, one study showed that the anthracnose pathogen infected more rapidly and severely in high density conditions, by 21%, in comparison to the standard planting method (Lindell et al., 2022).

Several factors can influence the effectiveness of high density sowing in the suppression of weeds. First, a uniform seeding pattern where the seeds are uniformly placed within the narrower rows has proven to be more effective in weed suppression (Xi et al., 2022). Moreover, weeding the field up to three times provides higher yield and will assist in better control of weeds (Chikoye et al., 2004).

High density planting systems not only increase competition between crops and weeds but also intraspecies competition (Dong et al., 2016). High density sowing can increase the competition for nutrients and decrease photosynthesis due to self-shading (Dong et al., 2016). This means that in the absence of nutrient-rich soil, many of the seedlings die before reaching maturity due to competition over resources (Zhang et al., 2022). Thus, high density sowing is not recommended in environments where there is no adequate water to ensure each plant develops (Zhang et al., 2022).

To maximize crop yield, farmers need to find the optimal sowing density that maximizes yield while keeping intracrop competition low (Ishikawa et al., 2022). The optimal sowing density varies based on the species of the crop, the environmental conditions, and the amount of fertilizer available (Ishikawa et al., 2022). When access to fertilizer is readily available, it can be used in combination with high density sowing to reduce intercrop competition (Ishikawa et al., 2022). Seed weight per plant is an easy-to-use indicator that allows farmers to determine yield through observation. This method is ideal for small-scale farmers to adopt to test crop yield under different conditions and densities and adjust their crop densities accordingly (Ishikawa et al., 2022). High density sowing increases interspecies competition and is often ineffective in intercropping systems (Sandhu et al., 2021). For example, in a system involving intercropping tomato and bell pepper plants, the biomass of the of the tomato plant was significantly decreased when the density was increased (Sandhu et al., 2021).

Implementation and helpful links

High density sowing is a simple technique that can be easily adopted by farmers in developing countries to improve crop yields and suppress weeds (Ishikawa et al.,2022). In simple terms, this method involves increasing the seeding rate and/or making more narrow rows (Province of Manitoba, n.d.). Implementing high density sowing can differ based on the crop and environmental conditions, and therefore testing for the density that produces the maximum yield is required before getting started (Ishikawa et al, 2022) such as small test plots in the first year. The only cost associated with high density sowing is purchasing seeds at a higher quantity (Ethridge et al., 2022). This cost can be negated by identifying areas that are at a higher risk of weeds and optimizing a strategy to primarily target those high-risk areas. (Ethridge et al., 2022). Some situations call for wide row spacing, in which wide rows can be used in combination with a higher seeding rate (Province of Manitoba, n.d.).

High density sowing is dependent on many factors such as environment, fertilizer and plant species (Akintoye et al., 2008). When implementing it on a farm for the first time, farmers need to experiment with different densities in order to find the optimum density (Ishikawa et al., 2022).

Here is a step by step guide to implement high density sowing to your farm:

1. Before beginning any experiments, assess your land to determine its size, soil type, drainage, and sunlight exposure.

2. Choose the crops you wish to experiment with based on factors such as market demand, suitability for your region, and your own preferences.

3. Identify a small plot of land on your farm where you can conduct the experiments.

4. Divide the plot into sections, with each section designated for a different crop density experiment.

5. Aim for a range of densities within each section, from low to high, to observe the effects of competition on growth and yield.

6. Regularly monitor the growth and development of the crops in each section. Note any signs of stress or competition-related issues.

7. During harvest, evaluate the yield and quality of the crops, taking note of any differences between the various density levels.

8. Analyze the data collected throughout the experiment to determine the optimal planting density for each crop.

9. Based on your analysis, adjust your farming practices accordingly.

Based on: (Deng et al., 2012; Ishikawa et al., 2022).

Here are some links to articles that can be helpful to small-scale farmers or organizations when implementing high density sowing:

https://www.youtube.com/watch?v=7MGzK9q89O0 High density spacing guide

https://www.youtube.com/watch?v=YU5D6_g3_2w&t=90s How watering smarter and high density sowing helps reduce weed

https://www.fao.org/3/i8848en/i8848en.pdf mitigating the impact of natural hazards in maize production

https://www.fao.org/3/v5330e/V5330e0l.htm introduction and use of density measurement

https://www.agrifarming.in/a-step-by-step-guide-to-high-density-fruit-farming-for-guava-banana-mango-pineapple-lemon-papaya-litchi-and-apple guide to high density planting in fruit

https://www.hedgesdirect.co.uk/acatalog/advice-on-planting-density.html a guide to planting density

https://www.canolacouncil.org/canola-encyclopedia/plant-establishment/seeding-rate/ guide to seeding rate for canola

https://cropaia.com/blog/planting-density/ maximizing crop yield using planting density

References

1.Akintoye, H. A., Lucas, E. O., & Kling, J. G. (2008). Effects of density of planting and time of nitrogen application on maize varieties in different ecological zones of West Africa. Communications in Soil Science and Plant Analysis, 28(13-14), 1163–1175.

2.Chikoye, D., Schulz, S., & Ekeleme, F. (2004). Evaluation of integrated weed management practices for maize in the northern Guinea savanna of Nigeria. Crop Protection, 23(10), 895–900.

3.Deng, J., Ran, J., Wang, Z., Fan, Z., Wang, G., Ji, M., ... & Brown, J. H. (2012). Models and tests of optimal density and maximal yield for crop plants. Proceedings of the National Academy of Sciences, 109(39), 15823-15828.

4.Dong, T., Zhang, Y., Zhang, Y., & Zhang, S. (2015). Continuous planting under a high density enhances the competition for nutrients among young Cunninghamia lanceolata saplings. Annals of Forest Science, 73(2), 331–339. https://doi.org/10.1007/s13595-015-0518-1

5.Ethridge, S. R., Locke, A. M., Everman, W. J., Jordan, D. L., & Leon, R. G. (2022). Crop physiological considerations for combining variable-density planting to optimize seed costs and weed suppression. Weed Science, 70(6), 687–697. doi:10.1017/wsc.2022.62

6.Gianessi, L. P. (2010). Solving Africa’s weed problem: Increasing crop production and improving the lives of women. Aspects of Applied Biology, 96, 9-23. Retrieved from https://www.cabidigitallibrary.org/doi/pdf/10.5555/20103346597#:~:text=Food%20production%20in%20Africa%20needs,lives%20of%20drudgery%20for%20fanners.

7.Ishikawa, H., Batieno, B. J., Fatokun, C., & Boukar, O. (2022). A high plant density and the split application of chemical fertilizer increased the grain and protein content of cowpea (Vigna unguiculata) in Burkina Faso, West Africa. Agriculture, 12(2), 199.

8.Lindell, C. A., Irish-Brown, A., Rothwell, N. L., & Wallis, A. E. (2023). Pest and disease risk and management in high-density perennial crops: Current knowledge and areas of future research. Crop Protection, 165, 106150.

9.Martins, J., Irvine, B., Entz, M., & Derksen, D. (n.d.). Weed Management Options: Seeding Rate and Row Spacing. Retrieved from umanitoba.ca website: https://umanitoba.ca/outreach/naturalagriculture/weed/files/singleseason/seed_rate_e.htm

10.Province of Manitoba (n.d.) Integrated Weed Management: Making It Work On Your Farm. (n.d.). Retrieved from Province of Manitoba website: https://www.gov.mb.ca/agriculture/crops/weeds/print,integrated-weed-management.html

11.Sandhu, R. K., Boyd, N. S., Zotarelli, L., Agehara, S., & Peres, N. (2021). Effect of planting density on the yield and growth of intercropped tomatoes and peppers in Florida. HortScience, 56(2), 286-290.

12.Subedi, G. D., Atreya, P. N., Gurung, C. R., Giri, R. K., & Gurung, Y. R. (2020). High density cultivation of major fruit crops: Opportunities and challenges in Nepal. In Proceeding of National Horticulture Seminar (pp. 94-107).

13.World Bank (2019) High-density Farming Diversifies Crops and Boosts Farmers’ Incomes. (2019, December 30). Retrieved from World Bank website: https://www.worldbank.org/en/news/feature/2019/12/31/high-density-farming-diversifies-crops-and-boosts-farmers-incomes

14.Wu, L., Deng, Z., Cao, L., & Meng, L. (2020). Effect of plant density on yield and quality of perilla sprouts. Scientific Reports, 10(1), 9937.

15.Xi, N., Wu, Y., Weiner, J., & Zhang, D.-Y. (2022). Does weed suppression by high crop density depend on crop spatial pattern and soil water availability? Basic and Applied Ecology, 61, 20–29. https://doi.org/10.1016/j.baae.2022.03.001

16.Zhang, Y., Xu, Z., Li, J., & Wang, R. (2021). Optimum planting density improves resource use efficiency and yield stability of rainfed maize in semiarid climate. Frontiers in Plant Science, 12, 752606.