The most important problems research had to solve were: (1). build-up and maintenance of soil fertility; (2). avoid soil hardpan and (3). control soil erosion.
The most important problems research had to solve were: (1). build-up and maintenance of soil fertility; (2). avoid soil hardpan and (3). control soil erosion.
研究要解决的最重要问题是：（1）积累和维持土壤肥力；（2）避免土壤硬磐；（3）控制土壤侵蚀。