Thread by @agribusinesszw

Chapter 1: Introduction to weeds: #INGESTA
@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 #agribusiness #farming #weed_control @SeedCoZim

Weed management is one of the most important parts of any successful…

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim …farming enterprise. Across the world the negative impacts of weeds are underestimated by many farmers, because the losses caused by weeds are not always seen immediately.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim Weeds are the most common crop pest, and in one hectare of agricultural soil there can be over 10 million weed seeds, and a million vegetative propagules. In order to win the battle against weeds in our fields we must first understand what makes weeds successfully our land.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim → What is a weed?
There are many different definitions of a weed, but the one we will use when discussing weeds is from the Weed Science Society of America: “a plant that causes economic losses or ecological damage, creates health problems for humans or animals, or is…

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim …undesirable where it is growing”.

→ Characteristics of a weed:
There are many characteristics that a plant must have in order to be a successful weed. These include:
• Seeds that can germinate in many different environments.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim • Seeds that can stay alive for a long period of time.
• Not all seeds germinating at the same time.
• Grows quickly before producing flowers.
• Seeds produced for as long as the growing conditions allow.
• Seeds produced quickly if growing conditions are good.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim • Some seeds produced even if growing conditions are not good.
• Reproduction is mostly cross-pollination (Sexual reproduction) to increase genetic diversity, but the plant has the ability to pollinate itself if necessary (Asexual reproduction).

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim • Cross‐pollination is done by unspecialised pollinators or by wind.
• Adaptations for short‐distance and long‐distance seed dispersal.
• Perennial species have quick vegetative growth and may be able to grow from small pieces.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim • Perennial weed species break apart easily so that the whole plant is not removed from the ground easily.
• Can compete aggressively with other plants.

→ Impact of weeds in sub-Saharan Africa:
In sub-Saharan Africa cultivation is mostly done by hand.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim This is highest in Central Africa, where 85% of the total land area is cultivated by hand. 70% of Western Africa, 54% of Southern Africa, and 50% of Eastern Africa are also cultivated by hand.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim Draught animals such as oxen are used to prepare 11% of agricultural land in Central Africa, 22% of agricultural land in Western Africa, 21% of agricultural land in Southern Africa, and 32% of agricultural land Eastern Africa [3]. Tractors are only used to prepare 4% of…

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim …agricultural land in Central Africa, 8% of agricultural land in Western Africa, 25% of agricultural land in Southern Africa, and 17% of agricultural land in Eastern Africa.

Preparing a field by hand is a difficult task and uses more energy (human muscle power) than any…

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim …other method of field preparation. This energy investment goes mostly to planting and weeding, which use up to 40% of the total energy needed to prepare a field by hand. Hand weed control requires many hours throughout the growing season.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim While there are many factors which affect the number of hours spent weeding a field, research [4] has shown that a farmer will hand-weed for approximately 276-309 hours per hectare of maize per season. This is more than 10 full days!

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim In one growing season a farmer will also spend approximately 150-324 hours per hectare of sorghum, 200-418 hours per hectare of rice, and 378 hours per hectare of ground nuts.

The number of times a field is weeded during a growing season will also influence yield.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim Research [5] has shown the following yields from cotton fields with different weeding strategies:
• 3 weedings in the season yielded 549 kg per hectare.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim • 2 weedings in the season yielded 400 kg per hectare (↓ 27%)
• 1 weedings in the season yielded 242 kg per hectare (↓ 55%)
• 0 weedings in the season yielded 71 kg per hectare (↓ 87%)

The timing of weeding is also very important.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim Research [5] has found that if the farmer weeded the field three times in the season, but delayed the first weeding by one week, the initial weed growth increased by 6000%. This requires twice the initial labour to clear the weeds from the field.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim It was also found that if the first weeding was delayed by two weeks the initial weed growth increased by 2000%, requiring three times the initial labour to clear the field of weeds. This is why it is so important to weed your fields while weeds are still small!

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim However, farmers are busy people and it sometimes becomes impossible for the farmer to keep up with controlling weeds in all their fields. In Malawi one-third of the maize fields of small scale farmers are left unweeded during critical stages of the growing season.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim Small scale farmers often leave up to 50% of their land unplanted, as they know they cannot control weeds over their whole farm for the whole growing season. Because of this weeds can cause yield losses of between 25 and 100% [8].

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim This learning programme is designed to give farmers an introduction into the basics of weed science and equip them with the knowledge to better manage their fields.

→ Summary:
There are many reasons why weeds are successful at invading our fields.

@Taona689068961 @zimagricsociety @zfu_official @Farm_Innovation @African_Farming @ZBCtv @corporatefarmg1 @SeedCoZim It is best to remove weeds while they are still small, as this uses less energy and reduces the negative effect they will have in your crop