This monitoring period (July to October 2020) covers the main growing season and harvest period of the following summer crops: soybean, maize and rice. Sowing of winter wheat started in September. As reported in the August CropWatch bulletin, conditions for planting and establishment of the summer crops were favorable, with a good supply of soil moisture until July. Close to average rainfall helped sustain crop growth during the grain filling phase. Slightly drier conditions in September and October provided good conditions for harvest. All in all, crop conditions for cereals were favorable.

Figure 1 crop phenology of United States between July and October

Figure 2 Crop condition development graph based on NDVI

During this monitoring period, close-to-average agro-climatic condition occurred and precipitation, temperature and radiation were 6%, 0.1℃, 0% below the 15YA. The potential biomass was 3% below the average due to reduced precipitation. During this monitoring period, the southeastern regions of the United States received above-average precipitation, while total rainfall was below average in the Corn Belt, Northern Plains and Western United States. California (-85%) was most affected, followed by Idaho (-32%), Minnesota (-30%), North Dakota (-35%), South Dakota (-39%), Iowa (-22%), Michigan (-15%) and Ohio (-19%). However, these deficits occurred mostly during the period from mid-September to mid-October (Figure 2).  The fraction of cropland impacted by drought conditions increased from 25% in July to about 40% in late-October. However, drier-than-normal conditions had little impact on yield as the crops approached maturity in September. Drier-than-normal weather actually improved harvest conditions.

Figure 3 Time series temperature pofile

Figure 4 Time series rainfall pofile

Figure 5 Dynamic changes in the proportion of drought

The great spatial heterogeneity in precipitation had caused significantly variation in crop conditions. The NDVI departure profile and cluster map shows that above-average crop conditions were widely observed in the southeastern USA, while average crop conditions were generally observed in the northern plains, northern Corn Belt, and western part of the country starting in September.  Crops don't require much water anymore in September as they are reaching maturity. Dry conditions during that month provide good conditions for harvest. Therefore, drops in NDVI in September had no negative impact on yield. A VCIx value higher than 0.8 also indicates that the crops in the southern corn belt were in good conditions. Although California suffered from severe precipitation shortages, its crop conditions were close to average, which may be attributed to developed irrigation infrastructures. Compared with the last 5 years, the cropped arable land fraction and the cropping intensity were both 1% below the average.  Considering the lower water requirements of the crops in September and October, CropWatch concluded that below-average precipitation and signs of drought conditions during these months had  little impact on final crop yields and crop conditions in the United States were generally favorable.

Figure 6 Spatial distribution of NDVI profiles

Figure 7 Maximum VCI

2. Regional Analysis

During this monitoring period, the biggest challenge for crop growth is insufficient precipitation during July and August. According to the distribution of crops in this current season, the analysis in this section focuses on the Corn Belt, Northern Plains, Northwest, Lower Mississippi, Southeast and Southern Plains.

2.1 Corn Belt

This is the most important corn and soybean producing area in the United States. It includes Illinois, Iowa, Minnesota, Wisconsin, Ohio and Michigan. Compared with the 15YA, this area experienced slightly below average precipitation during the monitoring period with below-average rainfall (-16%) and temperature (-0.6℃) and slightly above-average radiation (+1%). Significantly below-average precipitation occurred in  late August and September. In Iowa, total rainfall was 30% below the average. Fortunately, crops reached the maturity stage in September, so that reduced rainfall had little impact on crop yields. The crop condition development graph based on NDVI indicates that the crops were at their peak in late July and early August. NDVI subsequently dropped faster than usual, but this had no impact on crop yields, as maize reaches physiological maturity in mid-September.  CropWatch assessed the crop conditions as favorable.

Figure 8 Crop condition development graph based on NDVI

2.2 Northern Plains

This is the most important spring wheat and sunflower producing area in the United States and the second most important corn and soybean producing area. It includes North Dakota (Rain, -35%), South Dakota (Rain, -39%), Nebrask (Rain, -13%) and Montana (Rain, -4%). This monitoring period covers the grainfilling stages of spring wheat and the flowering and grainfilling stages of maize and soybean. This region had benefitted from slightly above-average precipitation during the April to July period. Compared with the 15YA, the northern plains had experienced drier weather conditions, with rainfall and temperature both lower than the 15YA (-19% and -0.1℃ respectively ). During the period of mid-September to early October, the Northern Plains experienced a rainfall deficit. Spring wheat was harvested in August and the water shortage had no impact on spring wheat. Maize and soybeans reach maturity in September and they were barely impacted by the drier-than-usual conditions. CALF was at 0.86, 6% higher than the 5YA. All in all, crop conditions were favorable for this region. 

Figure 9 Crop condition development graph based on NDVI

Figure.X Time series rainfall profile of northern plain

2.3 NorthWest

This is an important winter wheat producing area in the United States, including Washington (Rain, -7%) and Idaho (Rain, -22%). In the current season, this area experienced below-average precipitation, especially in Idaho. Compared with the 15YA, rainfall was 21% below average, temperature was 0.5℃ above average and PAR was 1% above average. The time series of rainfall shows that the rainfall in the northwestern region was significantly lower than average in July, August, and early September. Fortunately, the main crops in the area (winter wheat and barley) were harvested in July or early August and largely avoided the adverse effects of water stress. The NDVI development profile indicates that the crop conditions were close to the 5 year average until late September and crop conditions were average as well. 

Figure 10 Crop condition development graph based on NDVI

2.4 Lower Mississippi

This is the most important rice producing area and an important soybean producing area in the United States. It includes Arkansas, Louisiana, Mississippi and Missouri. The agro-climatic conditions in the lower Mississippi were close to the average with average rainfall (+ 3%) and temperature (-0.4°C), while the average PAR was 3% lower than the 15YA. The observed crop conditions were at average levels during the monitoring period. The VCIx value reached 0.95, which also confirmed the favorable crop growth conditions in this region.

Figure 11 Crop condition development graph based on NDVI

2.5 Southeast

This is an important cotton production area in the United States, including Georgia, Alabama and North Carolina.  During the monitoring period, the agro-climatic conditions in this region were favorable. Compared with the 15 YA, rainfall was 9% higher, temperature 0.2℃ lower and PAR 3% below average. Rainfall helped sustain vigorous crop growth, and the VCIx value reached 0.94. In general, the crop growth conditions were favorable in the region. 

Figure 12 Crop condition development graph based on NDVI

2.6 Southern Plains

This is the most important winter wheat, sorghum and cotton producing area in the United States. It includes Kansas, Oklahoma, Texas, and eastern Colorado. Texas is the largest cotton producing state in the United States. During this monitoring period, the southern plain experienced normal weather: Compared to the 15YA, rainfall did not deviate from the average, and temperatures were 0.5 ºC below average and PAR 1% below average. Winter wheat was completely harvested at the beginning of July, and this monitoring period covers the grainfilling period of sorghum, and setting bolls and harvest of cotton. The development profile of NDVI shows that the crop conditions were significantly below average. CALF was 8% below average. All in all, crop conditions were slightly below average. However, they varied greatly within the region, as shown in Figure 6. Especially the Texas pan handle and Colorado suffered from drought conditions.

Figure 12 Crop condition development graph based on NDVI

Table 3.1.United States’ agroclimatic indicators by sub-national regions, current season's values and departure from 15YA, July to October 2020

Table 3.2. United States’ agronomic indicators by sub-national regions, current season's values and departure, July to October 2020