The monitoring period for this report begins in January 2021 and ends in April 2021. During this period, winter wheat broke dormancy and reached the heading stage in late April in the southern regions. Spring wheat, corn, soybeans and rice planting started in late March and will last till early May. In general, the crop conditions were slightly below the 5-year average.

Nationwide, agro-climatic conditions were close to average during this period with a minor drop in precipitation (-5%), temperature (-0.5℃) and radiation (-2%) compared with 15YA. Significant below average precipitation occurred in California (-40%), North Dakota (-32%), Montana (-23%), Idaho(-20%), Indiana (-20%), and Michigan (-28%). In California, where extreme drought conditions were observed, most fields are irrigated. However, water supply is restricted since water levels in the  reservoirs in the  west of the USA  are already below average due to the prolonged drought conditions. 

In most wheat production regions of the USA, water is the most critical factor limiting yield. The top producer state of winter wheat, Kansas, had significantly higher than average precipitation by 20%, which was favorable for winter wheat growth. Oklahoma and Texas are also important winter wheat producing states in the U.S. Moderately above average and slightly below average precipitation occurred in Oklahoma (8%) and Texas (-4%), which provided normal soil moisture for winter wheat growth. A strong cold wave occurred in Mid-February. It seems that it did not cause much harm to winter wheat. Nationwide, the VCIx value of 0.75 indicates average crop conditions during this monitoring period. Pixels with low VCIx values (<0.5) were mainly located in the western Great Plains, where winter wheat growth was delayed. Colder-than-normal temperatures also hampered the sowing and emergence of spring crops. The cropped arable land fraction (CALF) was 5% lower than the average for the past 5 years. In short, the crop conditions assessed by CropWatch were slightly below average during this period. They were generally favorable for wheat grown in the Southern Plains, but unfavorable for the West and North-West.

Regional Analsysis

For the largest winter wheat producing region(Southern Plains) in the United States, the NDVI development profile and VCIx of 0.67 indicated below-average crop conditions for this period. During this period, precipitation was near average (5%), while temperature and radiation were significantly below the 15-year average at 1.5°C and 5% respectively. Potential biomass was 2% above average due to low temperatures and low solar radiation. A strong cold front swept across the southern plains in mid-February, causing a significant drop in temperatures (15℃ below the 15-year average). The abnormal low temperatures, accompanied by low RADPAR, resulted in delays of spring green-up of winter wheat. At the same time, CALF values were 10% lower than average compared to the 5-year average. As summer approaches, winter wheat will enter the grain filling and harvesting stage. CropWatch will be closely monitoring the changes in agri-climatic condtions, crop condtion, and yield of winter wheat in this region. 

The Northwest is the second largest winter wheat production region in the United States. The  NDVI development profile and VCIx of 0.65 in this period indicated below-average crop conditions. During this period, this region suffered a precipitation shortage by 17% as compared to the 15YA.  The crop condition development graph based on NDVI in the Northwest indicates below average crop development. Drier-than-usual conditions also negatively impacted the planting and germination of the summer crops, resulting in CALF being significantly lower by more than 30% as compared to the 5YA. Conditions are generally unfavorable for this region due to drought conditions. 

California is an important winter wheat producing region in the USA. The below-average NDVI development profile and VCIx of 0.60 indicated the poor crop conditions during this period. The region experienced severe drought with precipitation significantly below average by 41%. March and April are critical for winter wheat, as water requirements increases considerably once stem elongation starts. However, precipitation in the region has been significantly below average since February. The insufficient rainfall resulted in well-below average crop conditions as shown by the NDVI profiles. Although RADPAR was 8% higher than average, potential biomass was 22% lower than average due to the drought conditions. CALF was 17% below the 5YA.  Considering that California has a well-established agricultural irrigation system that can provide the necessary water for winter wheat growth, CropWatch assessed that the negative impact of drought on winter wheat yield as minimal.

Figure 1 Phenology of United States from January to April 2021

Figure 2 Crop condition development graph based on NDVI

Figure 3 Cropped and uncropped arable land

Figure 4 Maximum VCI

Figure 5 Spatial distribution of NDVI profiles

Figure 6 Crop condition development graph based on NDVI in Southern Plains

Figure 7 Time series temperature pofile in Southern Plains

Figure 8 Crop condition development graph based on NDVI in Northwest

Figure 9 Time series rainfall pofile in Northwest

Figure 10 Crop condition development graph based on NDVI in California

Figure 10 Time series rainfall pofile in California

Table 1 Agro-climatic indicators from January to April 2021 compared to 15YA

Table 2 Agronomic indicators from January to April 2021 compared to 5YA