The secret of better yield of Chinese broccoli in hydroponic
Growers of Chinese broccoli in hydroponic culture know that this crop is very special in terms of its requirements for the environment. Particularly, it is important to assess the most relevant ratio of ammonium and nitrate to determine the characters that have high heritability values. In the recent experiment, Indonesian scientists found the most appropriate ratio of this chemicals and the most productive variety of Chinese broccoli. They also used the mobile app Petiole to determine leaf area of crops.
How to grow Chinese broccoli in hydroponic culture and why?
Chinese broccoli (Brassica oleraceavar.alboglabra) is one of widely cultivated types of cabbage. It’s a leaf vegetable which has thick, flat, glossy blue-green leaves with thick stems. Also, it develops florets similar to broccoli. However, florets of Chinese broccoli are much smaller. The flavour is very similar to that of broccoli as well, but slightly more bitter. It is also noticeably stronger than broccoli. This oriental vegetable has tender edible stems, leaves, buds and flowers.
Chinese broccoli is a fast-growing crop rich in various vitamins, including vitamin A which is good for eye health. It is a great source of antioxidants and vitamin C. This green vegetable also contained isothiocyanate which is a well-known cancer-fighting compound.
It is possible to grow Chinese broccoli outdoors and sow into weed free, well prepared soil. Preferably, the soil pH has to be alkaline, than very acidic.
However, there is a global issue of a lack of agricultural land to grow crops. Hence, one of the modern alternative planting techniques could save land use, but also is able to produce quality healthy vegetables. This is a hydroponic planting technique. It offers many advantages, notably a decrease in water and land usage in agriculture.
Hydroponics for growing Chinese broccoli
Hydroponics, as a farming technology, uses water, nutrition, and oxygen media. As a result, hydroponic means growing plants in water containing nutrients.
Importantly, the nutritional solutions play a crucial role for the crop growth and development. There are two main groups of nutritional solutions in hydroponic systems, such as:
- nutrients containing macro elements (N, P, K, S, Ca, and Mg);
- nutrients containing micro elements (Mn, Cu, Mo, Zn, and Fe)
The difference between macro- and micronutrients is the amount which plants require. However, traditionally, plants need higher amounts of macronutrients than micronutrients.
Hydroponic systems are less forgiving than soil-based systems and nutrient problems can result in plant symptoms quickly. For that reason, the composition of the nutrient solution and regular monitoring of the nutrient solution and plant nutrient status is critical.
Dilemma of Chinese Broccoli Breeders and Growers
Chinese broccoli, as a leafy vegetable, needs high amount of nitrogen for its growth and development. When growing on hydroponic basis, plants absorb Nitrogen in the form of ammonium and nitrate.
If Nitrogen uptake by plants in the form of ammonium is almost 100% then there is an increase the availability of protein. At the same time ammonium is more efficient than nitrate in increasing the greenness of leafy vegetables. However, the negative impact of ammonium is linked to gradual deteriosis and a sharp decreased in dry weight due to damage to the root system.
Otherwise, if absorption was almost 100% in the form of nitrate, the impact was mainly on assimilation of the chemicals in the root. Additionally, some dose of nitrate was transported to the stem.
The presence of nitrates increased the concentration of macro elements like K, Ca, Mg, and P. The increase of these macro elements is observed in the roots. However, it also impacts the carbohydrate and carboxylic content. It is higher in the plant in comparison with the ammonium. The negative impact is related to the accumulation of excess nitrate in the stems. They are toxic to plants and sensitive to ammonium poisoning.
Hence, when developing a variety of Chinese broccoli grown well in hydroponic culture it is important to obtain the right ammonium and nitrate ratios for some Chinese broccoli varieties. As a result, correct determination of the ratio of ammonium and nitrate will help to discover high yield potential and production responses to Chinese broccoli. Also, it will be helpful to identify the varieties that have high heritability values.
Seven varieties and four nutritional solutions
A group of plant scientists from the Faculty of Agriculture of the Hasanuddin University in Indonesia decided to solve the dilemma of Chinese broccoli growers. In particular, the research group included Dr. Ir. Muh. Farid BDR, N Widiayani, Muhammad Fuad Anshori and Zulqaida.
Between August and October 2019 they conducted a research at the premises of the Screen House at the University of Hasanuddin Lecturer Residences, Tamalanrea Sub-district, Makassar, Indonesia.
Their study was arranged by using nested design and randomized complete block design as its environmental design. Additionally, replication was set in nesting to each ratio of ammonium and nitrate. The main factor included seven varieties of Chinese broccoli, namely:
- Full White
- New Veg Gin,
- Yama F1
- Sakura F1
- Nemo, and
The nutritional solution for hydroponics has different ratio of the ammonium and nitrate. It consisted of four levels such as:
- AB Mix;
- Solution with ammonium : nitrate (1 : 4 );
- ammonium : nitrate (1 : 8), and
- ammonium : nitrate (1 : 12).
Observation parameters for the experiment
During the experiment with Chinese broccoli, the scientists made the following observations:
- Measurement of plant height (cm) included the starting point at the base of the stem to the highest leaf tip at harvest (45 day after planting (DAP).
- The number of leaves (strands) was done by counting the leaves of plants that had been fully opened. Observations were made at the time of harvest (45 DAP).
- The pre-selected tool for leaf area (cm2) measurement was the Petiole Leaf Area Meter application and the time of measurement included the harvest period (45 DAP).
- Total weight (g) includes all parts of the plant at harvest (45 DAP).
- Shoot fresh weight or production (g) means weight of all parts of the plant except the root at harvest (45 DAP).
Results of the Experiment
The results of the experiment were discussed and published at the Second International Conference of Interdisciplinary Research on Green Environmental Approach for Sustainable Development, ICROEST 2020.
In the article with a title “Ratio of ammonium and nitrate to response of Chinese broccoli variety (Brassica oleracea Var. Alboglabra) in hydroponic culture”, the scientists demonstrated the outcomes of their observations.
Based on research that has been carried out, ammonium and nitrate ratios provided high growth and production response to Chinese broccoli with ammonium : nitrate ratio of 1 : 12 (171.8 g).
Varieties that have high growth and production responses in Chinese broccoli are New Veg Gin (214.04 g). Tables below represent the results of the experiment (credit to the authors of the research):
Finally, it is important to understand which approach the scientists use to find the plants with high heritability values. in fact, they used plant height, the number of leaves, leaf area, shoot fresh weight, and total fresh weight as the main criteria.
Please, find the text of the research paper and DOI of the article here.
Finally, if you are the author of a scientific research paper and used Petiole app or Petiole Pro in your research, please, refer to the mobile application and let us know about your paper.