Uncle Wang intends to surround a rectangular vegetable field with a circumference of 18 meters, and its length and width are all whole meters. How many different ways of enclosure are there? The rectangle obtained by each enclosing method. 18÷2=9 (m),

Since 9 = 1+8 = 2+7 = 3+6 = 4+5, there are four schemes, and the rectangular area enclosed by each scheme is as follows:

Scheme 1: 1×8=8 square meters;

Scheme 2: 2×7= 14 square meter;

Scheme 3: 3× 6 =18m2;

Scheme 4: 4×5=20 square meters.

Table below:

Judging from the four schemes, the rectangular vegetable plot with a length of 5 meters and a width of 4 meters enclosed by the scheme has the largest area.

Therefore, it should be suggested that Uncle Wang enclose this vegetable field according to the plan of 5 meters long and 4 meters wide.

Therefore, the answer is: the rectangular vegetable plot surrounded by the scheme with a length of 5, 4, 5 m and a width of 4 m has the largest area.