Agricultural extension – tireless footsteps: [13] Staggered custard apple cropping increases profit by VND 113 million/ha

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In recent years, alongside tea, custard apple has steadily affirmed its position as one of the key high-value crops for people living in the limestone mountain areas of Thai Nguyen. In Vo Nhai and La Hien communes, rocky hillsides that once generated modest incomes from maize growing have been transformed into large-scale commercial custard apple production areas.

However, the rapid expansion of cultivation has also brought numerous challenges. Traditional farming practices concentrate the harvest within a short period, resulting in large volumes entering the market simultaneously. This creates an oversupply, leading to volatile prices and economic efficiency that is incommensurate with the crop's potential.

Recognizing that enhancing the value of custard apple trees must begin with transforming production methods, the Thai Nguyen Agricultural Extension and Environment Center has implemented a science and technology application project to develop an intensive staggered-harvest custard apple cultivation model.

The difference lies in staggered cropping

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The Thai Nguyen Agricultural Extension and Environment Center, in collaboration with the Institute of Ornamental Organism Science at Viet Nam National University of Agriculture, trained six specialized technicians and organized four training courses for approximately 120 farmers. The Center also conducted numerous trials to monitor and evaluate the growth and development indicators of custard apple trees, with the aim of refining technical protocols suited to local conditions.

Based on the research findings, the intensive staggered-harvest custard apple cultivation model has been implemented across 3 hectares in the key custard apple-growing areas of the former Vo Nhai district, now Vo Nhai commune and La Hien commune. The model follows two production schedules: early-ripening/main-season and main-season/late-ripening custard apples.

According to Mr. Nguyen Dinh Thong, Deputy Director of the Thai Nguyen Agricultural Extension and Environment Center and project leader, the limestone mountainous terrain of Vo Nhai and La Hien communes, characterized by steep slopes and good drainage, provides ideal conditions for staggered-harvest custard apple cultivation.

Building on these natural advantages, the provincial agricultural extension system has focused on developing and transferring fertilizer application protocols suited to the limestone-mountainous terrain. Farmers have been advised to use microbial organic fertilizers in combination with biological preparations and to adopt fertilization methods that minimize nutrient losses.

The model's greatest difference lies not in fertilizer application but in techniques for regulating the timing of flowering and fruit set through branch pruning, canopy shaping, and artificial pollination.

According to the project's technical officers, pruning to shape the canopy plays a pivotal role in intensive staggered-harvest custard apple cultivation. When carried out in accordance with the recommended protocol, these practices enhance fertilizer use efficiency, reduce pesticide costs, lower harvesting labor requirements, suppress pest and disease incidence, and improve fruit quality.

For trees designated for the early-season/main-season harvest, pruning is carried out in January. Farmers are advised to choose dry weather conditions and prune the secondary branches at a point 20–25 cm from the main stem.

For trees intended for the main-season/late-season harvest, the removal of vegetative shoots from the trunk is performed in June, or no later than early July. After all shoots have been removed in accordance with the technical protocol, the trees are treated with pesticides to prevent pests and diseases, followed by the application of a flower bud differentiation stimulant to regulate flowering and fruit set in accordance with the planned production schedule.

In the custard apple-growing region of Vo Nhai, many farming households have cultivated the crop for decades and accumulated extensive practical experience. As a result, persuading growers to adopt cultivation practices that involve intensive intervention in the trees' growth and development was initially the project's greatest challenge.

Throughout the project, Ms. Ngo Thi Luyen, the project officer at the Thai Nguyen Agricultural Extension and Environment Center, worked closely with local farmers. Beyond organizing training courses and classroom instruction, she and technical officers regularly visited orchards and provided hands-on guidance.

"For any new production model, the most important thing is earning farmers' trust. At first, convincing growers to prune their trees was extremely difficult because many believed that heavy pruning would reduce yields. Moreover, custard apple trees are highly sensitive to weather conditions, so pruning must be carried out using the correct techniques and at the right time. During the initial stage, some farmers did not follow the recommended procedures properly," Ms. Luyen shared.

Many growers traditionally believed that leaving more branches on a tree would result in more fruit. However, the intensive staggered-harvest cultivation model requires the opposite approach, strategically removing branches so that the tree can concentrate nutrients, regulate flowering, and ultimately extend the harvest season.

Many participating households remained apprehensive during the early stages of implementation. Some pruned too lightly; others pruned too heavily; and some applied treatments at inappropriate times, causing the trees to respond differently than expected. As a result, technical officers closely monitored each stage of tree growth and made timely adjustments directly in the field.

It was not until the first year of implementation, when the trees began showing clear improvements in growth, fruit set, fruit quality, and most importantly, the ability to extend the harvesting period, that farmers became fully convinced of the model's effectiveness. Many households proactively applied the techniques on larger areas. The model also spread naturally, as participating farmers themselves shared their practical experiences with neighboring households.

Benefits of extended harvest seasons

Thanks to the effective application of the cultivation techniques, the custard apple orchards have maintained vigorous growth and achieved yields of 13–16 tons/ha. Compared with traditional production methods, the model not only increases productivity but also produces high-quality fruit, with an average weight of 250–300 g/fruit and a Brix value of over 17%.

Particularly, instead of harvesting within just 1-2 months as in the past, output is now spread across multiple periods. Early-season custard apples harvested in July account for 25-30% of total output; main-season fruit harvested in August and September makes up 55-65%, while late-season fruit harvested through October and November accounts for 10-15%.

Mr. Kieu Thuong Chat in Mo Ga hamlet, Vo Nhai commune, is among the model's largest participating households, cultivating 10 hectares of custard apple. By applying the recommended cultivation techniques in a coordinated manner, his family has significantly improved production efficiency while making better use of the region's favorable conditions.

The intensive staggered-harvest cultivation model generates a gross revenue of nearly VND 500 million/ha and a net profit of more than VND 366 million/ha, approximately VND 112.6 million/ha/year higher than conventional production. Average yields have also increased by 1.64 tons/ha compared with traditional cultivation practices.

"The agricultural extension officers have been extremely responsible. They not only organized training courses but also came directly to our orchards to provide hands-on guidance and monitor every stage of tree growth. Thanks to their support, we have gained a much better understanding of the techniques, applied them more effectively, and clearly seen the benefits of staggered-harvest cultivation. Farmers here truly appreciate the extension officers accompanying us throughout the process," Mr. Chat shared.

$1 = VND 26,466 - Source: Vietcombank.