Plant-water relation is one of the key focus of Ecohydrology, and it usually presents specific characteristics varying with climate, species and soils based on field studies. The large-scale plant-water relations in the Pearl River Basin were previously analysed and the hotspot for water and vegetation changes was identified in the cropland-dominated region. Here, we focused in this region and analysed how intensive agriculture could have modified or been affected by water resources in response to droughts. Pearson correlation analysis showed that the monthly vegetation change was more likely subject to energy availability while the annual change was mainly affected by precipitation and water storage. This cropland area experienced fairly frequent mild droughts, and the trend of a drought index SPEI showed a clear difference from that in the non-agricultural areas, particularly in growing seasons. Further examination showed that SPEI, vegetation parameters and agricultural data had strong positive relationships; vegetation parameters and water use varied significantly and positively with the planting structure and intensification of agricultural activities like fertilization and irrigation (r > 0.6, p < 0.05). A positive influence of droughts on crop production was detected, i.e. the mild droughts can promote productivity probably through firstly enhanced photosynthesis induced by enhanced solar exposure and secondly increased supplementary water supply by irrigation under drought. This study strengthens our understanding of the agriculture-water interactions in the humid subtropical region and has implications for agricultural water management and drought impact mitigations.