The fundamental distinction
The Rambam at the opening of the Book of Commandments (Root 1) divides all mitzvot into two types: positive commandments - an obligation to perform a certain action, and negative commandments - a prohibition against performing an action. The count: 248 positive commandments and 365 negative commandments, including the land-dependent mitzvot.
Positive mitzvot of the land
Positive mitzvot of the land, such as planting a tree and fulfilling the mitzvah of orlah (Vayikra 19:23), eating terumah and ma'aser, and bringing first fruits (Devarim 26:1-11) - require a positive action. In these mitzvot the partnership is clear: the agent performs the act with his body, and the partner funds the cost, and is considered as if he performed it.
Negative mitzvot of the land
Negative mitzvot of the land, such as the prohibition of kilayim (Vayikra 19:19), the prohibition of orlah (Vayikra 19:23-25), the prohibition of chadash (Vayikra 23:14), and the prohibition of harvesting one's field in the sabbatical year (Vayikra 25:4-5) - require abstention. How can one participate in a negative commandment? The partner funds the guarding and halachic supervision of the field, and the cost of abstaining from forbidden labor. Even in a negative commandment there is an active component - guarding and supervision - and one who partners in their cost is considered a partner in the mitzvah.
The source for partnership in both types
The Gemara (Sotah 14a) teaches: "Whoever assists those who perform a mitzvah, Scripture considers it as if he performed it." In negative commandments, one who assists with money in guarding the prohibition is considered as if he guarded it himself. On this basis, the Kerem 613 partnership encompasses both sides - both the positive and the negative.