Permaculture tries to look at a piece of land in a holistic manner, integrating every animal and plant living on it, and combining that with social structures designed to foster long-lasting agriculture as well. Each element of a food cycle is broken down into what it requires and what it contributes, and then each element is pieced together to form a dynamically self-supporting
whole. Hence, statement 3 is not correct.
High-density crops and the use of single crops over large expanses of land strips away necessary nutrients as generations pass, eventually leaving the land barren. So Permaculture discourages monoculture. Hence, statement 1 is correct.
At the same time, artificial fertilizers can build up salts over time, making the soil inhospitable to plants. Hence, statement 2 is correct.
Mulching is an important practice in permaculture. Hence, statement 4 is correct.