The 2019/2020 wheat season developed under a strong drought, with no relevant rains before or during sowing. Rains came by end June. Rains were scarce from July to the end of September. The drought affected fertilization, delayed weed emergence and made good control difficult. Rains normalized after September 30, approximately 120 mm in 45 days, reloading the soil profile and improving soil moisture.

Water stress lasted until early stem extension resulting in a wheat height 10 and 20 cm shorter (less internodes extension), poorer tillering and delayed appearance of stripe rust. Yield losses depended on each plot specific conditions. In properly managed plots with a 60 to 70 cm profile depth, yield losses were moderate. Lack of ears was compensated by a higher number and larger size grains. After adjusting fertilization, protein percentages were acceptable. Rains stopped by mid-November during grain filling, which negatively impacted on wheat final yield.

Wheat grew under different conditions in the central region, from Coronel Dorrego to the west (west of the province of Buenos Aires and La Pampa). October rains were light and started rather late. Drought impact on crops in more advanced cycles was harsher. Yields in this area were below those attained in the previous season. Closer to the coastal area, late October rains occurred before heading and were somewhat beneficial but, towards the interior of the subregion water stress resulted in a significantly lower number of grains.

Stripe rust roya (Puccinia striformis) was the most important disease that affected wheat with light attacks until late September but less aggressive than in previous growing seasons as a result of the drought. However, fungicide applications were necessary in almost every plot. After the rains, stripe rust roya attacked the susceptible cultivars. There were isolated attacks of leaf or orange roya (P. triticina) . Fusarium attacks were not as significant as in the 2018/2019 growing season as a consequence of water stress (low soil moisture) by end of grain filling.

October to maturity temperatures were appropriate; no heat stress affected the crop. Low relative ambient humidity and the absence of rains accelerated crop drying. Harvest started one week before than usual but heavy rains from December 19 to January 10 delayed its completion. Grains harvested late were washed by the rains; their test weight was below grade 3 in some cases.

Yields ranged from 2200 to 6500 kg/ha, with low test weight in wheat harvested after the December rains. Protein percentages, though, were generally all right thanks to N applications. Yield was over 80 q/ha in some plots close to the coastal area.

Appendix Of Locality Composite Samples

Appendix Of Locality Composite Samples