The Green Revolution
The Green Revolution occurred in the 1960s and 70s. In the first half of the 20th century, the increased use of fertiliser improved crop yields but enough food could still not be grown to support the growing human population. Ehrlich (1968) suggested that the human carrying capacity limit had been met and enough food could not physical be produced to sustain such large numbers of people. This prediction may have come to realisation, if it had not been for the Green Revolution and the developments made by Borlaug.
Figure 3: Dr Borlaug's Work and the Green RevolutionClick thumbnail to view full-size
Figure 1: Variation in Wheat HeightClick thumbnail to view full-size
The Role of Borlaug
Borlaug studied wheat and its yield in Mexico in the 1940s and 50s [Figure 3]. At that time, wheat was the main crop in Mexico for making tortillas, but the yield was only 0.75 t/ha. A large limitation in the yield was due to the stem rust fungus Puccinia graminis, which caused infected plants to produce fewer tillers, fewer seeds and sometimes death. Borlaug and his team tested wheat varieties for genes containing the resistance to the fungi. These plants were hybridised with ‘Norin 10’, a Japanese short-stemmed wheat, and then crossed with local Mexican wheat varieties. Although shuttle breeding was used, it took 9 years and 6000 crosses before progeny were found that possessed the desired traits and were able to grown in the Mexican climate. The result of this was that short-stemmed stem rust-resistant varieties of wheat were made that were adapted to suit the surrounding environment. The short stems were useful because it meant less carbon and energy was required for stem growth meaning that more was available for grain production increasing the yield per plant [Figure 1]. Shorter stems were also useful because it meant that the likelihood of lodging was greatly decreased. Lodging is when tall cereal crops fall over due to the weather, resulting in difficulties with harvesting and grain spoilage, but this is less likely to happen with dwarf varieties because the wind would be able to blow over them. This wheat was given as seeds to farmers, along with fertiliser, and they were educated about their usage. Consequently, the yield of wheat in Mexico was increased greatly, so that in the 1950s the yield was 6.5 t/ha, they were self-sufficient in 1956 and in 1964, ½ Mt wheat was able to be exported to other countries (Murphy, 2011).
In 1996 India wished to replicate this success because of a succession of poor harvests in the early 1960s, while there had been a large increase in population size, and the country did not have enough money to import food at such a large rate. 18000t of Borlaug’s wheat seeds were imported from Mexico. They were multiplied and crossed with local varieties. This was necessary because although Mexico and Indian have similar climates, India has different microclimates within it. Thus, in one year (1967 to 1968), the wheat yield had increased from 11.3Mt to 16.5Mt, including surplus crop that was not needed for consumption. Thus, the food crisis was solved so the population of 1.2 billion is self-sufficient and has been since 1968, without the need to convert land for agricultural uses (Murphy, 2011).
Therefore, Borlaug played a major role in the development of better crops growth with higher yields (Parris, 2011). This paved the way for other advances in other countries, allowing the Green Revolution to take place and making the growing global population be able to be fed and supplied for.
Figure 2: The Effect of the Green Revolution on Crop Yield in Mexico and IndiaClick thumbnail to view full-size
The Impact on Cereal Crop Yield
It is clear how vastly crop yields improved in wheat due to Borlaug and this Green Revolution, both in Mexico and India [Figure 2]. However, wheat was not the other crop to be affected by these developments.
A similar to strategy to that of Borlaug’s was applied to rice by Beachell and the International Rice Research Institute (IRRI) in the 1970s. By screening and crossing of rice varieties, ‘miracle rice’ (IR8) was created from the rice varieties Peta and Dee Geo Woo Gen. It was a semi-dwarf variety with a thick stem and a high yield, reducing the likelihood of lodging due to high levels of precipitation. This shorter height was due to a spontaneous mutation in the sd1 gene, altering the activity of gibberellin, reducing stem elongation. The miracle rice caused the worldwide rice production to double from 257 to 600Mt from 1966 to 2000, of which, 90% was in Asia, directly due to the progress done by the Green Revolution.
The Use of Inputs
The dwarf plants have naturally low yields without inputs, such a NPK (nitrate, phosphorus and potassium) fertiliser. Nitrates are used by plants to synthesise the amino acids that are required for proteins, so if a plant is deficient in it, it would have stunted growth. Phosphorus is a component of nucleic acid and so regulates protein synthesis, with deficiency causing stunted growth and a dark green colour. Potassium ensures the ionic environment in the cytosol is correct, with deficiency causing chlorosis and reduced development.
Fertilisers are added to the soil to support plant growth because crops can deplete them. This happens especially because of continuous farming, for example on the best land. To solve this crop rotation occurred in the 18th century. For the first three years cereals would be grown and the fourth year would have a break crop that is not a cereal, for example oilseed rape or legumes. The land would also be allowed to be fallow, for example by leaving the ground to have just grass and animals, where the animal manure would fertiliser the grass. Although this was not an efficient method, since crops would not be able to be produced on every field, it kept the soil in good condition.
In the 1850s it was worked out how manure helps the soil; that nitrate, phosphorus and potassium were required. The Haber Process of 1910 provided the nitrate from the harnessing of atmospheric nitrogen to form ammonia and then oxidising it. The phosphorus and potassium came from mining.
Although these are initially given out for free by the government in developing countries (as well as the seeds), later farmers had to buy it. This process favours the relatively richer farmers. This causes the poor farmers to sell their land to those who are richer and leave to go to cities for jobs because they cannot afford to survive through their traditional agricultural background. This is why Mae Wan Ho argues that there are social issues of the green revolution, making the poor be disadvantaged. However, these ideas are based on opinion rather than scientific fact and without such methods there would not be enough crops to feed the growing population. Furthermore, it could even be said that it is better for the environment if this fertiliser is not subsidised. This is because in China it is subsidised, encouraging the over-application of fertiliser. This is an issue because if there are too many solid fertiliser pellets on a field, it does not have time to dissolve by the rain into the soil. This causes the excess fertiliser to run off into the water course, resulting in nutrient saturation (eutrophication) which causes cyanobacterial and algal blooms. They produce toxins which cause fish death resulting in decreased biodiversity. However the problems with run-off can be solved with farm management, when nutrient production cannot. Thus this fertiliser is of utmost importance in the process of Green Revolution, to continue the growth and high yield of the dwarf crops.
It could also be said that no matter what methods are adopted, there will always be a battle between human welfare, animal welfare and the environment. An example of this is that enough food has to be provided for the expanding human populations, which can be done with the use of inputs, but this may have negative knock-on effects to the surrounding organisms and the environment. If the inputs were not used, it would be the human population that would need to be controlled. This could be done with two different routes: coercive and voluntary. The coercive route was taken by China in 1960 with its one child policy and India with the sterilisation of females for money. However, these methods could be considered as unethical for humans because the people were unable to make their own life choices and may not understand the implications of sterilisation. The voluntary route is achieved by countries having more reliable incomes and so fewer children, due to an increased survival rate. However, although this would solve the problem with the expanding human population, economic growth may harm the environment and other organisms, for example mining.
Therefore even though fertilisers can have ethical issues concerning the environment, they are required to make the crops produced by the Green Revolution a feasible method of feeding the growing human population. This makes them a vital part of the agricultural process. Furthermore, because the newer varieties of crops mature faster, meaning that they can be grown more intensively, the soil deplete even faster than when using traditional crops.
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