The monitoring period covers the whole cycle of summer maize from July to late September, as well as the sowing and early growing season of winter wheat from early October. The NDVI development graph displays generally slightly below-average crop condition.
The NDVI values were below 5YA from July to early August, but then improved to 5YA until harvesting. For early October, coinciding with early stage of winter wheat, NDVI values fell slightly to below 5YA again.
Agro-climatic conditions include a 26% decline in precipitation compared to average, affecting mainly early growth of maize. The temperature and the radiation rose by 0.8℃ and 4% compared to 15YA, respectively. The slight drop in NDVI during the growing season of maize may be influenced mainly by poor precipitation, which led directly to a 1% drop in BIOMSS. Besides, low NDVI values in early October had no effect on the BIOMSS index. The maximum VCI value for Huanghuaihai was 0.89.
As shown by NDVI clusters and profiles, 20.7% of cropland over northern Anhui and Jiangsu, as well as some scattered areas across the whole region, displays average condition during almost the whole period. 41.9% of cropland over southern Hebei, western Shandong and northern Henan suffered below-average condition before August and recovered to average during September. Remaining areas had negative NDVI departure values all the time. The spatial distribution of biomass departures displays a drop not exceeding 10%; more significant reductions are noted in Beijing and some scattered areas in Shandong and Henan. Increases only occur in eastern Henan and northern Anhui and Jiangsu.
In general, crop condition in Huanghuaihai was below average due to severe water stress at early growing stage, but recovered to average level since mid-August.
Figure 4.14. Crop condition China Huanghuaihai, July 2019 - November 2019
(a) Crop condition development graph based on NDVI
(b) Rainfall profile
(c) Temperature profile
(d) Spatial NDVI patterns compared to5YA (e) NDVIprofiles
(f) Maximum VCI