**2. Phenology of sesame**

Sesame is a survivor crop. For 5500 years it has been planted by subsistence growers in areas that will not support the growth of other crops or under very difficult growing conditions with drought and/or high heat. In some countries, it is grown after the monsoon season on residual moisture with no rains during the production stage while in other areas it is grown during the monsoon season and subject to daily rains during the growing season. In several countries, it is the last crop that can be grown at the edge of deserts where no other crops grow. Very little sesame is grown under high input conditions [18].

placenta attachment has dried, and in many varieties, the capsules also may have a dark seed line on one side as shown in **Figure 2**. However, there is world germplasm

*The capsule on the bottom has seed that is milky white and is not mature. The capsule on the top has seed with*

There are cultivars where the yellowish green color of the capsule will indicate that the seed inside the capsule is at PM. However, there are other cultivars where the capsules are dark green with PM seed inside, and still other cultivars where the capsules are a pale yellow with immature seed inside. Before using capsule color to

The concept of PM in sesame was developed in the 1950s (M.L. Kinman, personal communication, 1982) to determine the earliest date that the plants could be cut and still harvest over 95% of the potential yield. When the seed has the final color, the seed can germinate. If the sesame is cut at PM, most of the seed with a greater than 75% darker color will continue maturing sufficiently for germination

*PM seeds have a brown tip (red arrow) where the placenta attachment has dried and on one side of the seed, a*

where the seed line is present but not visible without a magnifying glass.

*Effects of Harvest Aids on Sesame (*Sesamum indicum *L.) Drydown and Maturity*

*DOI: http://dx.doi.org/10.5772/intechopen.91011*

tell PM, the grower must be familiar with the cultivar.

**Figure 1.**

**Figure 2.**

**209**

*seed line is visible (blue arrow) (Photo: D.R. Langham).*

*final color (Photo: J. Riney).*

There are four phases in the phenology of sesame: vegetative, reproductive, ripening, and drying and there is a tremendous amount of variability in these phases [19]. Sesame is an indeterminate species, and thus, there is an overlap between the reproductive, ripening, and drying phases [18]. Since this chapter deals with sesame desiccation only the ripening and drying phases will be discussed.

Technically, as an indeterminate species, sesame is in the ripening stage from the mid-bloom stage through the full maturity stage. Sesame starts self-defoliation in late bloom stage and leaves have mostly fallen off by the initial drydown stage. As the plant stops flowering and matures, the leaves will drop starting at the bottom of the plant. In some fields, the upper leaves can remain attached providing some photosynthesis for seed fill in the upper capsules. Generally, leaves will turn yellowish green before dropping [18].

The character of leaf drop is very important for mechanical harvest and for using harvest aids. There is world germplasm where the leaves do not drop and can remain green even with a dry, open capsule in the leaf axil. Through plant breeding, the ability to self-defoliate has been incorporated into germplasm in the Americas starting in Venezuela from the mid-1940s [20].

At PM, 75% of the capsules on the main stem have seed with final color (darker than the milky white of the immature seed) as shown in **Figure 1**. Most of the seed grown for edible purposes is a light color, but there are cultivars with brown and black seed. The darker colors at PM are easy to distinguish from the milky white immature seed. Physiological mature seed also will have a brown tip where the

*Effects of Harvest Aids on Sesame (*Sesamum indicum *L.) Drydown and Maturity DOI: http://dx.doi.org/10.5772/intechopen.91011*

#### **Figure 1.**

leaves, and/or seeds in the bin, the moisture will transfer from the weeds to the sesame [17]. Extensive work in Venezuela to dry sesame by passing it through dryers showed that it was too expensive and that if more than 1% of moisture was removed per pass through the machines, the seed quality deteriorated to an unmarketable level (MAVESA representatives, personal communication,

• Glyphosate, carfentrazone-ethyl, and pyraflufen-ethyl are non-selective herbicides that will kill the sesame and the weeds; however, they are not desiccants. Among these, glyphosate is a better weed killer. Glyphosate should

• Paraquat-dichloride and diquat-dibromide are desiccants and may not kill

• Glufosinate-ammonium is a non-selective herbicide, but also will dry the

Sesame is a survivor crop. For 5500 years it has been planted by subsistence growers in areas that will not support the growth of other crops or under very difficult growing conditions with drought and/or high heat. In some countries, it is grown after the monsoon season on residual moisture with no rains during the production stage while in other areas it is grown during the monsoon season and subject to daily rains during the growing season. In several countries, it is the last crop that can be grown at the edge of deserts where no other crops grow. Very little

There are four phases in the phenology of sesame: vegetative, reproductive, ripening, and drying and there is a tremendous amount of variability in these phases [19]. Sesame is an indeterminate species, and thus, there is an overlap between the reproductive, ripening, and drying phases [18]. Since this chapter deals with sesame

Technically, as an indeterminate species, sesame is in the ripening stage from the mid-bloom stage through the full maturity stage. Sesame starts self-defoliation in late bloom stage and leaves have mostly fallen off by the initial drydown stage. As the plant stops flowering and matures, the leaves will drop starting at the bottom of the plant. In some fields, the upper leaves can remain attached providing some photosynthesis for seed fill in the upper capsules. Generally, leaves will turn

The character of leaf drop is very important for mechanical harvest and for using

At PM, 75% of the capsules on the main stem have seed with final color (darker than the milky white of the immature seed) as shown in **Figure 1**. Most of the seed grown for edible purposes is a light color, but there are cultivars with brown and black seed. The darker colors at PM are easy to distinguish from the milky white immature seed. Physiological mature seed also will have a brown tip where the

harvest aids. There is world germplasm where the leaves do not drop and can remain green even with a dry, open capsule in the leaf axil. Through plant breeding, the ability to self-defoliate has been incorporated into germplasm in the Americas

not be used for seed sesame because it can affect the germination.

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*

weeds. They are based on contact with the sesame surface.

sesame down at a comparable rate to the desiccants.

• Tolerance to some herbicides is cultivar dependent.

sesame is grown under high input conditions [18].

yellowish green before dropping [18].

**208**

starting in Venezuela from the mid-1940s [20].

desiccation only the ripening and drying phases will be discussed.

1983).

**2. Phenology of sesame**

*The capsule on the bottom has seed that is milky white and is not mature. The capsule on the top has seed with final color (Photo: J. Riney).*

placenta attachment has dried, and in many varieties, the capsules also may have a dark seed line on one side as shown in **Figure 2**. However, there is world germplasm where the seed line is present but not visible without a magnifying glass.

There are cultivars where the yellowish green color of the capsule will indicate that the seed inside the capsule is at PM. However, there are other cultivars where the capsules are dark green with PM seed inside, and still other cultivars where the capsules are a pale yellow with immature seed inside. Before using capsule color to tell PM, the grower must be familiar with the cultivar.

The concept of PM in sesame was developed in the 1950s (M.L. Kinman, personal communication, 1982) to determine the earliest date that the plants could be cut and still harvest over 95% of the potential yield. When the seed has the final color, the seed can germinate. If the sesame is cut at PM, most of the seed with a greater than 75% darker color will continue maturing sufficiently for germination

#### **Figure 2.**

*PM seeds have a brown tip (red arrow) where the placenta attachment has dried and on one side of the seed, a seed line is visible (blue arrow) (Photo: D.R. Langham).*

but may be lighter in weight. Even in a fully mature plant, the seed weight produced at the top of the plant is lower; however, this loss of seed weight does not seriously affect the potential seed yield of the plant. Physiological maturity is important in the northern US crop where there is a potential for an early frost or freeze. After PM, most of the potential yield can be harvested, even if the plants were terminated by cold temperatures. In south Texas, the rule of thumb is that PM moves up 6–7 node pairs per week below the 75% PM level, and 4–5 node pairs per week above the 75% level. At higher latitudes where night temperatures are cooler, the progress of PM is 3–4 node pairs per week below the 75% level and 1–2 node pairs above it. The threshold temperature for growing degree days of sesame is 16°C. When night temperatures go below the threshold, it takes longer for the crop to mature. Physiological maturity also delineates the earliest time that harvest aids should be applied; applying them earlier will reduce potential yield.

The drying phase is divided into three stages: full maturity, initial drydown, and late drydown. Full maturity occurs from PM until 90% of the plants have all seeds mature. This stage usually occurs from 107 to 112 days after planting and lasts for approximately 1 week. With direct harvest, without the use of harvest aids, this stage is not important. With harvest aids, the plants will be killed, and the seeds will no longer fill. At the end of this stage, the plants will have the highest potential yield and can be terminated to accelerate drydown. However, since the capsules in the top 2–3 node pairs contribute little seed, the practical time to apply harvest aids may be at some point between PM and when all seeds are mature.

The above paragraphs show nominal days for one cultivar in the USA. There is a

Generally, if a cultivar starts flowering early, it will also stop flowering, mature,

Due to the shattering nature of the capsules, in most of the world, the sesame needs to be cut when green and shocked (stacking in bundles) so less seed will fall

Growers will cut the plants before the capsules start opening. Over 99% of the sesame harvest in the world involves some or total manual labor to cut the sesame, and no plants are left standing to dry in the field. Therefore, most of the sesame is harvested during or at the end of the ripening phase. Once shocked, the capsules will start drying and opening. Since the sesame is stacked and in a shock, which does not bend in the wind, most of the seed will stay in the capsules with some falling out of the top. In a commercial field in Venezuela, the author examined shocks that

*The plants are cut before the capsules start drying even though they have leaves and are not completely mature to*

and dry early. The point is that if a crop is left in the field to drydown without harvest aids, it takes about 5–6 weeks to be dry enough for a combine to harvest. If

**Phase Days from planting Length of phase, days**

*Effects of Harvest Aids on Sesame (*Sesamum indicum *L.) Drydown and Maturity*

Vegetative 29–59 42 29–59 42 Reproductive 56–116 89 16–70 47

Drying 102–181 150 11–57 38

*In some lines, there are dry capsules above green leaves while the upper part of the plant is still flowering creating*

**Range Mean Range Mean**

–54 11

range in the world germplasm planted in the USA (**Table 1**).

Ripening 77–140 108 (14)<sup>a</sup>

it is in the rainy season, it could take longer.

**3. Shattering nature of sesame**

*Range of days in phases for world germplasm.*

*DOI: http://dx.doi.org/10.5772/intechopen.91011*

*a*

**Table 1.**

**Figure 3.**

**211**

*the top (Photo: D.R. Langham).*

*a negative range.*

out as the plants dry (**Figures 3** and **4**).

The initial drydown stage occurs from the time all seeds are mature until the sesame plants have one dry capsule. This stage typically occurs 113–126 days after planting and can last for up to 2 weeks. This is a unique stage for most sesame that is grown in the Americas. In the world germplasm, a few cultivars have dry capsules with a green leaf in the same leaf axil, and many cultivars have a dry capsule when the top of the plant is still flowering. As a result, growers cut the plants to prevent seed loss and create a situation where some of the seed is mature and other seed is immature. In the Americas, the capsules do not drydown and open until flowering is complete and the majority of seed fill is complete. This character is described as "delayed shattering" (W. Wongyai, personal communication, 1998). Since sesame is basically indeterminate, the ability to stop flowering is difficult. There is germplasm that will stop flowering based on daylength; others that will stop based on cold nights; but most stop when they run out of moisture and/or fertility. The only problem with the latter germplasm is potential regrowth, which will be discussed later. A potential problem with delayed shattering is vivipary, which also will be discussed later.

The main stem will generally have dry capsules before the branches; however, the branches will generally drydown before the main stem. The lower capsules dry first with the top capsules drying last. There are some cultivars where the bottom capsules at the 2–3 node pairs drydown late even though the seed is at PM. Parts of the stem will dry before all the capsules are dry.

The late dry-down stage occurs from the time of the first capsule drydown until enough dry-down has occurred to produce 6% or less moisture seed. The first capsule drydown usually occurs 127 to 146 days after planting and the late drydown stage can last up to 3 wks. If the reproductive phase is shorter because of a lack of fertility, the first capsule drydown will occur a shorter time from planting but will not necessarily change the length of time of the late-drydown stage. However, if the reproductive phase is shorter because of a lack of moisture, the first capsule drydown will have a shorter time from planting and a shorter length of time of the late dry-down stage.

*Effects of Harvest Aids on Sesame (*Sesamum indicum *L.) Drydown and Maturity DOI: http://dx.doi.org/10.5772/intechopen.91011*


*a In some lines, there are dry capsules above green leaves while the upper part of the plant is still flowering creating a negative range.*

#### **Table 1.**

but may be lighter in weight. Even in a fully mature plant, the seed weight produced at the top of the plant is lower; however, this loss of seed weight does not seriously affect the potential seed yield of the plant. Physiological maturity is important in the northern US crop where there is a potential for an early frost or freeze. After PM, most of the potential yield can be harvested, even if the plants were terminated by cold temperatures. In south Texas, the rule of thumb is that PM moves up 6–7 node pairs per week below the 75% PM level, and 4–5 node pairs per week above the 75% level. At higher latitudes where night temperatures are cooler, the progress of PM is 3–4 node pairs per week below the 75% level and 1–2 node pairs above it. The threshold temperature for growing degree days of sesame is 16°C. When night temperatures go below the threshold, it takes longer for the crop to mature. Physiological maturity also delineates the earliest time that harvest aids should be applied; applying them earlier will reduce potential

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*

The drying phase is divided into three stages: full maturity, initial drydown, and late drydown. Full maturity occurs from PM until 90% of the plants have all seeds mature. This stage usually occurs from 107 to 112 days after planting and lasts for approximately 1 week. With direct harvest, without the use of harvest aids, this stage is not important. With harvest aids, the plants will be killed, and the seeds will no longer fill. At the end of this stage, the plants will have the highest potential yield and can be terminated to accelerate drydown. However, since the capsules in the top 2–3 node pairs contribute little seed, the practical time to apply harvest aids may

The initial drydown stage occurs from the time all seeds are mature until the sesame plants have one dry capsule. This stage typically occurs 113–126 days after planting and can last for up to 2 weeks. This is a unique stage for most sesame that is grown in the Americas. In the world germplasm, a few cultivars have dry capsules with a green leaf in the same leaf axil, and many cultivars have a dry capsule when the top of the plant is still flowering. As a result, growers cut the plants to prevent seed loss and create a situation where some of the seed is mature and other seed is immature. In the Americas, the capsules do not drydown and open until flowering is complete and the majority of seed fill is complete. This character is described as "delayed shattering" (W. Wongyai, personal communication, 1998). Since sesame is basically indeterminate, the ability to stop flowering is difficult. There is germplasm that will stop flowering based on daylength; others that will stop based on cold nights; but most stop when they run out of moisture and/or fertility. The only problem with the latter germplasm is potential regrowth, which will be discussed later. A potential problem with delayed shattering is vivipary, which also will be

The main stem will generally have dry capsules before the branches; however, the branches will generally drydown before the main stem. The lower capsules dry first with the top capsules drying last. There are some cultivars where the bottom capsules at the 2–3 node pairs drydown late even though the seed is at PM. Parts of

The late dry-down stage occurs from the time of the first capsule drydown until

enough dry-down has occurred to produce 6% or less moisture seed. The first capsule drydown usually occurs 127 to 146 days after planting and the late drydown stage can last up to 3 wks. If the reproductive phase is shorter because of a lack of fertility, the first capsule drydown will occur a shorter time from planting but will not necessarily change the length of time of the late-drydown stage. However, if the reproductive phase is shorter because of a lack of moisture, the first capsule drydown will have a shorter time from planting and a shorter length of time

be at some point between PM and when all seeds are mature.

the stem will dry before all the capsules are dry.

yield.

discussed later.

of the late dry-down stage.

**210**

*Range of days in phases for world germplasm.*

The above paragraphs show nominal days for one cultivar in the USA. There is a range in the world germplasm planted in the USA (**Table 1**).

Generally, if a cultivar starts flowering early, it will also stop flowering, mature, and dry early. The point is that if a crop is left in the field to drydown without harvest aids, it takes about 5–6 weeks to be dry enough for a combine to harvest. If it is in the rainy season, it could take longer.

#### **3. Shattering nature of sesame**

Due to the shattering nature of the capsules, in most of the world, the sesame needs to be cut when green and shocked (stacking in bundles) so less seed will fall out as the plants dry (**Figures 3** and **4**).

Growers will cut the plants before the capsules start opening. Over 99% of the sesame harvest in the world involves some or total manual labor to cut the sesame, and no plants are left standing to dry in the field. Therefore, most of the sesame is harvested during or at the end of the ripening phase. Once shocked, the capsules will start drying and opening. Since the sesame is stacked and in a shock, which does not bend in the wind, most of the seed will stay in the capsules with some falling out of the top. In a commercial field in Venezuela, the author examined shocks that

#### **Figure 3.**

*The plants are cut before the capsules start drying even though they have leaves and are not completely mature to the top (Photo: D.R. Langham).*

#### **Figure 4.**

*The plants are placed in shocks to dry. The leaves shrivel quickly, but it will take about 2–3 weeks to dry, particularly in center of shock (Photo: D.R. Langham).*

were about 75% dry and found that about 10–15% of the seed had fallen out. That evening, it rained about 10 mm, and two days later the outer bundles in the shock had lost 20–40% of the seed, while the inside bundles which had not been wet were still at about 10–15% loss. **Figure 5** shows a similar Mexican commercial variety after a rain. Shattering is necessary for a manual harvest (**Figure 6**) where minimal force is used to get the seed out of the capsules.

direct may lead to as much as 90% loss of seed as discovered in 1978–1980 with

*Improved non-dehiscent capsule. These capsules hold their seed better and will still release it in the combine. This photo was taken on Dec 17 when the crop could have been combined the first week of Oct. The seed is still in*

*the capsules 76 days after the plants were dry enough for combining (Photo: D.R. Langham).*

*Shattering is essential to release seed as in this photo. Many growers hold the sesame plant upside down and hit with an implement. Some seed is lost while drying in the shock; other seed is lost in handling the sesame from the shock to the threshing area but upon threshing 95–100% of the remaining seed is collected (Photo: N. Smith).*

*Effects of Harvest Aids on Sesame (*Sesamum indicum *L.) Drydown and Maturity*

*DOI: http://dx.doi.org/10.5772/intechopen.91011*

In the 1940s, D.G. Langham [20] harvested sesame by using a binder to cut and bind the sesame at maturity. The sesame was manually shocked and when dry, the bundles were thrown into the combine header. Langham [21–23] discussed the history of improving shatter resistance in the USA. Basically by 1982, there was enough shatter resistance to be able to swath sesame into a windrow and leave it on

attempts to harvest shattering varieties left to dry in the field.

**Figure 6.**

**Figure 7.**

**213**

Since the 1940s, the goal in Venezuela and the USA has been to completely mechanize the sesame harvest. Leaving a shattering cultivar in the field to harvest

**Figure 5.** *More seed shattered out than usual with some capsules still green because of rain (Photo: D.R. Langham).*

*Effects of Harvest Aids on Sesame (*Sesamum indicum *L.) Drydown and Maturity DOI: http://dx.doi.org/10.5772/intechopen.91011*

#### **Figure 6.**

were about 75% dry and found that about 10–15% of the seed had fallen out. That evening, it rained about 10 mm, and two days later the outer bundles in the shock had lost 20–40% of the seed, while the inside bundles which had not been wet were still at about 10–15% loss. **Figure 5** shows a similar Mexican commercial variety after a rain. Shattering is necessary for a manual harvest (**Figure 6**) where minimal

*The plants are placed in shocks to dry. The leaves shrivel quickly, but it will take about 2–3 weeks to dry,*

*Pests, Weeds and Diseases in Agricultural Crop and Animal Husbandry Production*

Since the 1940s, the goal in Venezuela and the USA has been to completely mechanize the sesame harvest. Leaving a shattering cultivar in the field to harvest

*More seed shattered out than usual with some capsules still green because of rain (Photo: D.R. Langham).*

force is used to get the seed out of the capsules.

*particularly in center of shock (Photo: D.R. Langham).*

**Figure 4.**

**Figure 5.**

**212**

*Shattering is essential to release seed as in this photo. Many growers hold the sesame plant upside down and hit with an implement. Some seed is lost while drying in the shock; other seed is lost in handling the sesame from the shock to the threshing area but upon threshing 95–100% of the remaining seed is collected (Photo: N. Smith).*

direct may lead to as much as 90% loss of seed as discovered in 1978–1980 with attempts to harvest shattering varieties left to dry in the field.

In the 1940s, D.G. Langham [20] harvested sesame by using a binder to cut and bind the sesame at maturity. The sesame was manually shocked and when dry, the bundles were thrown into the combine header. Langham [21–23] discussed the history of improving shatter resistance in the USA. Basically by 1982, there was enough shatter resistance to be able to swath sesame into a windrow and leave it on

#### **Figure 7.**

*Improved non-dehiscent capsule. These capsules hold their seed better and will still release it in the combine. This photo was taken on Dec 17 when the crop could have been combined the first week of Oct. The seed is still in the capsules 76 days after the plants were dry enough for combining (Photo: D.R. Langham).*

the ground instead of shocking it manually. The windrows were harvested with a combine equipped with a pickup attachment. By 1988, the shatter resistance had improved to the point where the sesame could be left in the field to dry and then cut. The goal had been to have the seeds stay in the capsules until the combines arrived and then release the seed in the combine with a minimum of force. Improvements continued with the development of non-dehiscent sesame [24, 25] and later improved non-dehiscent sesame [25]. The seed would stay in the capsules through wind and rain even after the plants were dry enough to combine (**Figure 7**). for the stem to reach this moisture level leading to more seed loss in the field. Also, desiccation did not have an effect on defoliation, and the ability to harvest earlier through desiccation increased seed yield. In a grower book, Bennett et al. [32]

*Effects of Harvest Aids on Sesame (*Sesamum indicum *L.) Drydown and Maturity*

reduced shattering but seed loss was still evident even while waiting for sufficient drydown to spray (**Figure 8**). Also, there was still more loss when the cutter bar struck the sesame and the sesame was being moved by the auger into the feeder

Bennett and Routley [33] studied diquat-dibromide at 0, 1.4, 2.6, and 5.3 L ha<sup>1</sup> and time of application (97 DAP with 40% green capsules, 103 DAP with 18% green capsules, 109 DAP with 0% green capsules, and untreated) in the 1993 and 1994 growing season using the sesame variety, Y1:44. Results indicated that application rates of 2.0 L ha<sup>1</sup> were cost effective and that time of application should be between 20 and 40% green capsules. They also concluded that desiccation was a risk management tool. Sesame naturally drying down can be exposed for 30–40 days of various weather conditions, including rains and high winds**,** while a desiccated crop has a drydown of 7–10 days and, therefore, less of a chance of being exposed to inclement weather conditions. Also, desiccation allows the grower to

Mazzani [34] summarizing sesame research in Venezuela stated after almost 30 years of research and grower experience, the recommendations were to use diquat-dibromide at 1 kg ha<sup>1</sup> at normal cutting time, which resulted in only a 15% lower yield over the untreated. Applying diquat-dibromide at 2 kg ha<sup>1</sup> a week earlier than normal cutting time resulted in 97% seed loss due to immature seeds. The desiccation system is 4–8% of the cost of traditional system of cutting, binding, and shocking. Mazzani (personal communication, 1999) said that the timing of the herbicide application required grower experience of the sesame maturity stage based on capsule color and variety instead of number of days from emergence. Also, combining after using diquat-dibromide could be a bit earlier than the traditional method. Using the traditional shocking method, the inner bundles in the shocks take longer to drydown resulting in high risk, since the start of the monsoon season can occur while the sesame is still in shocks. One of the major advantages of using desiccants is that there is less manual labor available at harvest for cutting and shocking. On the negative side, the use of desiccants may produce less yield than the traditional method, particularly if there is a wind during drydown, which may cause

*Sesame on the ground even before combining from using dehiscent varieties (Photo: M. Bennett).*

. This application rate

recommended a diquat-dibromide application of 3 L ha<sup>1</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.91011*

housing of the combine.

**Figure 8.**

**215**

plan for contract harvesting and trucks.
