Scientific developments in agriculture and technologies of chemical fertilizers and pesticides fed the "green revolution" of the mid-20th century. Still, a few decades later, pollution and toxins from those chemicals became evident. Now, climate change, partially caused by agricultural technologies, has also moved to the centre of our preoccupations. These environmental problems, as well as economic and social inequities, incentivize the search for more sustainable agricultural technologies that can be brought about by deeper scientific insight. Replacing chemical fertilizers with less harmful products, which we can refer to as organic fertilizers, while still maintaining crop production capable of feeding the global population, is an objective for farmers, policymakers, and, in fact, for everyone. In today's world, science and technology move forward rapidly, pervading every aspect of social and individual lives; keeping in touch with them is necessary for each of us in our field of work. This book aims to help us replace chemical fertilizers with organic ones. In the following chapters, the reader can find reviews of recent developments and reports of experimental works on organic fertilizers that might help better understand their advantages and drawbacks.