The queue of more than 2,600 trucks stretched for 58 km and almost reached the city of Kovel. Trucks are slowly moving towards the Yagodin checkpoint.
[...]
Several factors contributed to the traffic jam at the Polish border.

The first—Ukrainian farmers harvest and sell it to neighboring countries. According to the Ministry of Agrarian Policy, 625,000 tons of food was exported by road transport in August, which is seven times more than in April.
[...]
The second is that Poland should speed up the phytosanitary inspection of Ukrainian cargoes, because now Ukraine exports three times more food by road. However, cargo inspection has slowed down. According to [UA] Deputy Minister of Infrastructure Mustafa Nayem, at the end of August, the speed of phytosanitary inspection decreased four times compared to the pre-war period.

The third is strikes by Polish truck drivers, who are blocking the road. They are protesting because of the loss of the opportunity to travel outside the queue. ... This may become a difficult test for the Ukrainian economy. Highways through the western border are the largest source of foreign currency for Ukrainian exporters and a reliable shoulder during the port blockade. 40% of all automobile exports of Ukraine account for the checkpoint in Yahodyna. ...

Statement by the United Nations Coordinator for the 'Black Sea Grain Initiative' Amir Abdulla, 27 Aug
"The silos in Ukraine are still stocked with millions of tons of produce from previous harvests. The Black Sea Grain Initiative has started creating some space but much more grain needs to shift to make space for the new harvest."
JCC | Black Sea Grain Initiative Joint Coordination Centre Operational Update --departures to IT, TR
"As of 19 August, the total tonnage of grain and foodstuffs exported from the three Ukrainian ports is 656,349 metric tons."
archived UN | JCC Progress report, 1-15 August 2022