By K. R. Kranthi
International Cotton Advisory Committee, Washington DC
India has enormous potential for cotton farming. Given the ideal climatic conditions and the natural sources, doubling the cotton farmers’ income should not actually be a big task for India. Globally, countries have been constantly increasing their yields over the past 20 years at least, without increasing fertilizers, pesticides and water. There are a few simple technologies that are being followed almost uniquely in six countries (Australia, China, Brazil, Mexico, Turkey and USA -hereafter mentioned as leader-countries), that harvest more than 3000 Kg seed-cotton per hectare as National average.
These technologies are listed below:
Varieties with high harvest index (boll weight / total plant weight)
Intra-row spacing of 10 cm between plants (high density planting)
Canopy management to increase harvest index
These technologies have been coupled with precision management of crop duration, light, water and nutrients to obtain high yields in a short time of 150 days. Scientists in the six leader-countries have been constantly working to enhance harvest index through proper agronomy to ensure that the crop gets adequate nutrients and water when it needs them the most. Thus water-use-efficiency and nutrient-use efficiency are almost optimized in these countries in a sustainable manner. It is a matter of great concern that the Indian harvest index ranges from 0.17 to 2.0 in contrast to 0.35 to 0.5 in the leader-countries. It is important for Indian scientists to introspect and question as why India ranks a poor 32-34 in yields in the world despite being saturated with hybrids (two Bt genes), high fertilizer usage, excellent sunshine, good rains and irrigation.
High Harvest Index
Undoubtedly, high harvest index is the key word for India to double cotton farmers’ income and could hold the secret to achieving a break through. By increasing harvest index, Indian scientists can easily help farmers to double their yields without increasing any inputs such as water, fertilizers and pesticides. The key to success would depend on plant breeding for compact varieties with least monopodial branches, shorter height, shorter duration, tolerance to sap sucking insects and synchronous boll opening. The role of agronomists, soil scientists and physiologists is crucial in increasing harvest index. They should develop simple methods of soil health management and canopy management while crop protection scientists must effectively create systems that conserve and promote natural and cultural control of insect pests and diseases, which eventually plays a major role in enhancing input-use-efficiency. Indian cotton scientists must focus on the development of best practices that are required for plant mapping, canopy management, soil reclamation, soil conservation, cropping systems, conservation tillage, water-use-efficiency, nutrient-use-efficiency, pest management, weed management are crucial for yield enhancement (Kranthi, 2018).
Indian cotton receives abundant sunlight, adequate rainfall and a good amount of fertilizers which should have ideally resulted in high yields due to good crop growth. However, it is paradoxical that these ideal conditions coupled with the hybrid technology could actually working against the crop leading to poor harvest index, thereby causing low yields. India needs varieties that do not produce excessive unproductive vegetation which eventually leads to wastage of natural resources such as water and nutrients. Unfortunately, the hybrid technology does just the opposite. The ideal climatic conditions promote excessive vegetative growth, which needs to be curtailed at critical crop stages either through mechanical methods or with the use of plant growth regulators to ensure a proper nutrient source-sink relationship as is being done in the leader-countries. However hybrid vigour is difficult to control even with plant growth regulating chemicals.
It is true that a few farmers in India manage to obtain high yields with good crop management that generally includes drip irrigation and chemical intensive practices. However, the number of such farmers is miniscule, and these practices cannot be replicated in the fields of resource-poor farmers. Interestingly, in the six leader countries, the yields of almost all farms are closer to the high national average. India should aim to increase yields in the fields of resource-poor farmers through good science.
There is a stark contrast in the plant breeding objectives of India and the six-leader countries. The biggest contrast is that while ‘India is saturated with hybrid cotton and harvests about 1400 to 1500 Kg seed-cotton per hectare, the leader-countries are saturated with varieties but harvest three-fold higher yields than India. Seed-cotton yields are 4000 to 5000 Kg/hectare in Australia, China, Turkey, Brazil and Mexico. The contrast extends to the scientific approach as well. While, over the past 30 years plant breeders in the leader-countries developed compact-architecture short-statured, short-duration cultivars that retain an optimum number of bolls, generally at 15-20 bolls per plant, Indian plant breeders have been constantly striving to develop big and bushy plant types that produce highest number of 80-150 bolls per plant. The contrast continues in agronomists and physiologists. While, Indian scientists focused on wide spacing between plants that suited the bushy varieties and also to facilitate inter-culture, hoeing and harrowing between plants, elsewhere in the leader-countries, scientists were busy developing systems for effective light penetration, input-use-efficiency and canopy management for high density planting that dwarfed the crop to make it amenable for machine picking. Yields have been increasing constantly in Australia, Turkey, Brazil and China over the past 15 years, but stagnated in India during this period. There is clear evidence a low planting density approach of keeping a wide spacing (30 to 90 cm or more) between plants in a row invariable leads to mediocre yields of 1200 to 2000 Kg seed-cotton. There could be exceptions with pampered input-intensive management in a few Indian farms, but these wouldn’t be sustainable either ecologically or economically. Sadly, Indian yield rank continues to be 32-35th in the global list of cotton growing countries, sometimes ranking below the national average of a few resource-poor African countries such as Cameroon, Cote D’ivoire, Mali etc., which neither have BT nor hybrids nor proper input access.
India is currently suffering a paradox of ‘low yields with hybrids’. Hybrids compel farmers to plant in low density because of high seed cost and hybrid vigour which makes canopy management a nightmare. The low density of 11,000 to 20,000 plants per hectare warrants long duration for high yields so that each plant produces more number of bolls. The hybrids are designed for hybrid vigour which results in excessive vegetative growth and large number of monopodial branches. Indian hybrids average at 4.5 monopodial branches in contrast to 1-2 in the leader countries. The hybrids in India must produce more bolls per plant; the plants take a longer time for higher yields, or if terminated prematurely result in low yields. Unfortunately, this factor puts spokes in the wheel for high yields.
India has thus inconveniently moved into a rigmarole situation where a long duration crop is necessary for high yields. However, with the pink bollworm developing resistance to BT-cotton, the late season bolls could be eaten up by the worms. Thus, it wouldn’t be wrong to say that Indian cotton is actually stuck between the devil and the deep sea. If rains are good, the extended crop suffers pink boll worm and reduces yields, and if the rains are bad the crop gets terminated soon resulting in low yields. This strange predicament could continue as long as the dependence on ‘high-boll-load-hybrid-plants’ would continue through a long duration crop. However, this year could be an exception of the above phenomenon because last year (2018), the crop was terminated in time due to poor rains, leaving less scope for the pink boll worm to attack this year. Despite the good rains, India may not be able to harvest more than 560 Kg lint per hectare. This year (2019) the crop received excessive rains for it to be extended 2-3 months beyond December thereby providing good inoculum of pink bollworm for the 2020 crop. Indian scientists must be on the guard to protect the crop from the pink bollworm in 2020.
Cotton plants need about 80% water and nutrients during the flowering and boll formation stage, which is referred as ‘the critical window’. Incidentally the critical window is most vulnerable to bollworms; any stress during this time adversely affects the yields depending on the level of stress (Kranthi, 2018). A low density crop (as in India) leads to longer duration of the critical window (80-120 days) leading to stress of nutrient and water availability, whereas, a high density crop (>100,000 plants per hectare) has a short season and therefore a short critical window (50-60 days) that could get access to water and nutrients based on a well-planned planting time.
India must seriously consider working towards increasing the harvest index to achieve a breakthrough in yields. Improved harvest index improves the input-use-efficiency of water and nutrients. The following passages are reproduced from Kranthi (2018).
India needs to seriously consider development and evaluation of the following systems:
1. Cultivars with high harvest index;
2. High density planting;
3. Canopy management;
4. Best practices.
Cultivator With High Harvest Index :
Plant breeders must seriously consider developing cultivars with the following features 1. Compact-short-statured plants; 2. Zero-monopodial type; 3. Short season (140-150 days); 4. Resistance to sap-sucking insects and local pathogens; 5. High initial shoot and root vigour; and 6. High ginning% and good quality fibre. These attributes lead to a high harvest index apart from enabling a short critical window that leads to less management problems related to nutrients, water and pests. Compact statured plants with short intermodal length are known to be more efficient in channelizing water and nutrients to fruiting parts such as flowers and bolls. Canopy management becomes easier with plants that are designed to be genetically compact. Resistance to sap sucking pests helps to avoid early pesticide applications so that natural control can be conserved to help in bollworm management. Early or timely planting of the short-season crop generally helps the crop to escape the American bollworm and the late-season pink bollworm infestation. High ginning% leads to higher lint output and therefore high economic yields.
High Density Planting:
Agronomists should seriously consider standardizing optimum plant spacing and try a geometry of 8-10 cm between plants in a row. Planting direction must be adjusted to avoid shading and to harness sunlight. Sowing time must be adjusted to synchronize boll formation phase with monsoon. Planting on ridges or raised beds protects the crop against seedling pathogens, competition from weeds, waterlogging and drought effects.
Canopy Management:
Indian scientists must focus on crop monitoring and canopy management with an objective to increase the harvest index. Agronomists must explore plant growth regulators and mechanical techniques of canopy management to ensure optimum plant growth and to avoid unproductive vegetative growth. Removal of unproductive branches and biomass or restricting vegetative growth with growth regulating chemicals reduces boll shedding, increases boll size, increases the number of fruiting nodes, enhances the dry mass of fruiting parts and increases seed cotton yields.
Best Practices:
Soil health is mostly a function of good soil management practices that include, conservation tillage practices, cropping systems, soil management, nutrient management, soil-moisture management, minimizing chemical toxicants, nitrogen fixation by plants and organic matter that is returned back to the soil as crop residue biomass that in-turn is microbially converted to organic manure. While, best agronomic practices can ensure adequate water and nitrogen to seedlings and key nutrients to flowers and green bolls for high yields; IPM and IRM are crucial for pest management in India, especially with the recent challenge posed by the BT-resistant pink bollworm. Cultivars that are resistant to sap-sucking insects held in avoiding early pesticide use and thus hold the key to the consolidation of natural control which keeps bollworms under check. Several legume intercrops such as beans, cowpea, black gram etc., host predators and parasitoids of insect pests apart from fixing nitrogen.
For about the past twenty years, the private sector hybrids have dominated the Indian cotton seed market. Though Indian plant breeders have done commendable work, in the past 20 years, the excellent varieties developed by them did not occupy even a fraction of the area over the past two decades. Cotton scientists from other disciplines have also been struggling to find relevance. The sole exception was that entomologists had a role in recent times in developing technologies to combat the Bt-resistant pink bollworm. It is sad indeed that such a potential scientific resource pool had to be relegated to a lesser role in the national cotton scenario.
At this juncture, it would be important for the Indian cotton scientists to rediscover their role by first introspecting as to why India ranks below 32nd rank in yields? Why the yields have been stagnating over the past 15-years despite doubling of fertilizer use? And what could be done to break the yield-jinx. Indian cotton needs a breakthrough. With what is available in their kitty, it is unlikely that the private sector would be able to assist with yield improvements or a better pest management. There is no evidence that the three gene BT-cotton (Cry1Ac+Cry2Ab+VIP3A) can protect the crop from the pink bollworm. There is no evidence that HT has a significant advantage over manual or mechanical weeding. There are no new technologies in sight. Therefore, it is important for Indian cotton scientists to gear up and start building multi-disciplinary teams with objectives of enhancing yields without any increase in input use through novel approaches.
Changing the mind set of researchers and farmers for new approaches such as compact plants with fewer bolls per plant, would be a great challenge in itself. But, these ideas are worth exploring because they have succeeded in countries such as Australia, Brazil, China, Mexico, Turkey and USA, that are placed in divergently different geographical areas, different agro-ecological zones and with a very different socio-economic and cultural structure. These basic suggestions are based on success stories and standard practices being followed in the developed countries.
It should be remembered that a success story from a developed country may not find resonance in developing or underdeveloped countries which are placed in completely different geographical domains and have a very different socio-economic profile. However, lessons can always be learnt from anywhere and adapted to local conditions through rigorous experimentation and validation (Kranthi, 2018).
Good scientists never shy away from experimenting new ideas. If the yield-stagnation jinx has to be broken, new ideas must be tried and tested so that effective alternatives can be developed. Success will eventually depend on how determined researchers are try new things to make a change (Kranthi, 2018).
Reference:
Kranthi, K. R. (2018) A change in plant architecture can break the yield barriers in Africa. The ICAC RECORDER XXXV1 No.3 September 2018. Pp 25-30
By K. R. Kranthi
International Cotton Advisory Committee,
