The noticeable differences are often the result of weather conditions such as the drought in 1988, or the flood and wet weather at planting time in 1993.
(The noticeable differences; are; T:often; the result of weather conditions such as the drought in 1988, or the flood and wet weather at planting time in 1993)
The noticeable differences
are
T:often the result of weather conditions such as the drought in 1988, or the flood and wet weather at planting time in 1993