Dearest Narjes Bay, you are emphatically right, we have exhusted agricultural lands and fertilizers to their elastic limit however, we have not explore biotechnology yet to improve and increase productivity. Bio-technologies include mutation breeding, which we have practically tried on yam to increase it small sizes to larger ones through mutant varieties, there is GMO, where the natural process of selections and adaptations is facilitated through laboratory experiments to get the best yield which can be adaptable to the yet climate. There is also selection of best seeds for cultivation but due to demand and drudgery farmers don't have time to go through seed selection as done by early fathers.

And there are a lot more we haven't discovered yet and we are becoming slow in discovering them because of the fashion and reward that have been put in place for scientists. Most scientist focus are on publications for promotion more than researching to achieve some new discoveries that can change life in the long run.

Even if we feed more the land, the plantation can accept the feed to certain level. Still, if we want speed growth of plants, research is required, in such  a way that the plants can accept overdose of fertilizers.

During my study in the United Kingdom, I came to know of a research which was going on at Sheffield University in which the researchers were trying to synthesize artificial enzymes which mimic the natural enzymes. The artificial ones were to be injected into plants to catalyze or speed up growth. However, a good choice of fertilizers can help. Consider the fertilizer ammonium nitrate; the ammonium ions are slow-releasing while the nitrate ions are fast-releasing. Therefore, adding this fertilizer together with some potassium nitrate will aid fast growth together with a good amount of water. However, taking care of plants by cutting dry parts & removing nearby grass can also lead to rapid growth.

Several growth hormones are in the markets so they will do the job for you