Good morning, ladies and gentlemen. Thank you for waiting. At this time, we would like to welcome everyone to SLC Agrícola's [second] quarter 2019 earnings conference call. Today, we have with us Mr. Ivo Marcon Brum, CFO and Investor Relations Officer. We would like to inform you this event is being recorded, and all participants will be in listen-only mode during the conference presentation. After the conference remarks are completed, there will be a question-and-answer session. At that time, further instructions will be given. Should any participant need assistance during this call, please press star zero to reach the operator. Also, today's live webcast, both audio and slideshow, may be accessed through the SLC Agrícola website at www.slcagricola.com.br in the Investor Relations section by clicking in the banner Webcast 2019. The following presentation is also available to download on the webcast platform.
The following information is available in thousands of Brazilian Real and the IFRS, except when otherwise indicated. Before proceeding, let me mention that forward-looking statements are based on the beliefs and assumptions of the SLC Agrícola management and on the information currently available to the company. They involve risks, uncertainties, and assumptions because they relate to the future events and therefore depend on the circumstances that may or may not occur in the future. Investors should understand that general economic conditions, interest rate conditions, and other operating factors could also affect the future results of the company and could cause results to differ materially from those expressed in such forward-looking statements. Now, I will turn the conference over to Mr. Ivo Marcon Brum, CFO and Investor Relations Officer. You may proceed.
Good morning, and welcome for our conference call. Let's go, please, to slide three. The international scenario for agricultural commodity price, as you can see in the chart, has been highly volatile, which is due to three main factors. Trade war between United States and China, the African swine fever event in China, and the condition for the 2019-2020 crop in the United States. Given this new scenario of greater uncertainty with new variables in play, it's important to remember the policies that you have adopted to successfully cross more volatile periods such as this. On slide four, you can see the summary of our hedge position. With over 90% of our cotton and soybean already sold for 2019, at a price well above the current spot market.
Our corn crop is already 80% sold at an average price of BRL 23.4 per bag, which is 17% higher than the sales price of 2018. Our industry operates with long cycles, which means that we have an ample window of time to take decisions on locking prices in order to avoid negative fluctuation in the short and medium term. Let's turn to slide six, please. Our operational performance also works to protect our business by guaranteeing high levels of competitiveness in the business. The soybean harvest has at last concluded in April with a final yield already announced in the first quarter, slightly higher than last year and 6% higher than our initial estimate.
For cotton, with nearly 230 of our crops harvested to date, our yield estimate was revised back to initial estimate following the heavy rains in May, which caused losses in the base of the plants, especially in Northeast. Corn yield, with 80% of harvest concluded, is estimated at 7.1 tons per hectare, 4.5% above the budget. Let's move to slide eight. In the first semester of the year, our results were again very positive, with records for net revenue, volume invoiced, and adjusted EBITDA. EBITDA grew 6.5% on 2018 due to the 12% increase in gross income. Despite the higher gross income, net income was slightly lower than in the first half of the last year, reflecting the dynamics in the booking of biological assets for soybean due to the crop early maturation this year.
There was a higher percentage of the fair value of the biological assets booked in December 2018, as well the implementation of the IFRS 16. In the quarter, adjusted EBITDA was lower than the second quarter of last year, mainly due to the lower soybean volume invoiced. The lower soybean volume invoiced is explained by anticipation of invoicing this year with a higher share of the crop invoiced in the first quarter. In the six-month period, soybean volume invoiced is higher than the same period of crop 2018. Cotton and corn volume invoiced also grew with margin expansion. Net income in the quarter advanced at 26% year-on-year, mainly due to the higher apportionment of the variation in the fair value of biological assets, reflecting the largest cotton area. Let's move to slide nine.
Free cash flow in the first six months of the year was negative at around BRL 400 million, reflecting the higher working capital needs in the period, mainly due to the strong expansion in the cotton area in the 2018, 2019 crop year. Note that the first half of the year is when payments of the agricultural inputs are made. However, the second half of the year will be marked by the invoicing of the bulk of the cotton crop, supporting strong cash generation without any increase in the working capital needs. On slide 10, you can see that during the first semester, we also paid dividends for the fiscal year 2018 of BRL 186 million and concluded the share repurchase program, in which BRL 42 million were invested.
As a result, adjusted net debt, which you can see on slide 11, increased from BRL 943 million at the end of the last year to BRL 1.6 billion, which corresponds to 2.3x adjusted EBITDA in the last 12 months. To support these higher working capital needs, we successfully raised BRL 360 million through the local bonds with interest of 99% of the CDI rate and amortization in fourth and fifth years. Thank you, and let's go to open the call to questions.
Ladies and gentlemen, we will now initiate the question- and- answer session. If you would like to ask a question, please dial star one. If at any point your question has been answered, you may remove your question from the queue by pressing the pound key. Please wait while we collect some questions. Remembering, if you have a question to do, please dial star one. Thank you, all. This does conclude today's presentation. You may disconnect your line at this time.