Learn English – It’s important to learn / learning a language when you’re young

In terms of grammar, either form is perfectly acceptable. The preferred usage will certainly vary by region, but in my personal experience, the gerund is definitely the more common form, whereas the infinitive can often sound dated and awkward. However, I have certainly heard the infinitive used well, especially in more formal contexts.

"X is important to learn" would mean that it is important that you learn X.

"X is important to learning Y" would mean that in order to learn Y, X is important. In this case, in order to learn about what will help farmers use wet soil, the scientific work on crops in standing flooding is important.