| Disaggregation of revenue |
The following table presents the Partnership’s revenue, disaggregated by major product: | | | | | | | | | | | | | | | | | | Three Months Ended
September 30, | | Nine Months Ended
September 30, | (in thousands) | 2019 | | 2018 | | 2019 | | 2018 | Ammonia | $ | 11,110 |
| | $ | 11,391 |
| | $ | 74,416 |
| | $ | 51,361 |
| UAN | 61,970 |
| | 52,681 |
| | 199,576 |
| | 156,838 |
| Urea products | 4,575 |
| | 4,987 |
| | 14,251 |
| | 14,834 |
| Net sales, exclusive of freight and other | 77,655 |
| | 69,059 |
| | 288,243 |
| | 223,033 |
| Freight revenue | 8,752 |
| | 8,805 |
| | 23,909 |
| | 23,908 |
| Other revenue | 2,175 |
| | 2,045 |
| | 5,963 |
| | 6,024 |
| Net sales | $ | 88,582 |
| | $ | 79,909 |
| | $ | 318,115 |
| | $ | 252,965 |
|
|
| Summary of deferred revenue activity |
A summary of the deferred revenue activity for the nine months ended September 30, 2019 is presented below: | | | | | (in thousands) | | Balance at December 31, 2018 | $ | 68,804 |
| Add: | | New prepay contracts entered into during the period (1) | 24,121 |
| Less: | | Revenue recognized that was included in the contract liability balance at the beginning of the period | 67,823 |
| Revenue recognized related to contracts entered into during the period | 8,174 |
| Other changes | 480 |
| Balance at September 30, 2019 | $ | 16,448 |
|
(1) Includes $23.7 million where payment associated with prepaid contracts was collected.
|