Effect of Protein Hydrolysate-based Amino Acid Fertilizers on Fruit Quality of Citrus

Abstract: Taking citrus as the research object and soybean protein hydrolyzed amino acid fertilizer as the test material, the effect of amino acid fertilizer on the chlorophyll content of spring shoot leaves, fruit color and quality of citrus was studied. The results showed that the proteolytic amino acid fertilizer was sprayed on the citrus at the time of 2/3 of the flowers withered, and the effect was better by spraying once every 20 days and continuously spraying it for three times.

In the experiment, water spraying was used as the control, and four fertilizer spraying treatments were set up. Starting from 2/3 of citrus flowers withered, 800 times of amino acid fertilizer was sprayed every 20 days. The first spraying time of each treatment was different by 20 days. During the annual growth period, each treatment was sprayed 3 times, each spray is limited to dripping water on leaves and fruit surfaces. The amount of protein hydrolyzed amino acid fertilizer sprayed in each treatment was 800 times of liquid (preliminary test results showed that the spraying concentration effect was better).

1. Effects on chlorophyll content of citrus spring shoot leaves

Compared with the control, the chlorophyll content of the spring shoots of citrus increased significantly when the amino acid fertilizer was sprayed on the citrus at the time of 2/3 of citrus flowers withered and 60 days after the 2/3 of citrus flowers withered, and the increase rates were 20.6% and 22.6%, respectively.

2. Effects on the coloration of citrus fruits

The chromaticity of the peels treated by spraying proteolytic amino acid fertilizers were all positive. The chromaticity value was significantly higher than that of the control when the amino acid fertilizer was sprayed on the citrus at the time of 2/3 of citrus flowers withered, also, the fruit is orange-red with good brightness.

3. Effects on physical properties of citrus fruits

Compared with the control, the transverse diameter of the fruit treated with amino acid fertilizer increased significantly. The overall performance of single fruit quality is the best when the amino acid fertilizer was sprayed on the citrus at the time of 2/3 of citrus flowers withered. The peel was thinner and the edible rate increased by 2.8%.

4. Effects on the intrinsic quality of citrus fruits

The contents of total sugar, soluble solids and vitamin C in the treatment of spraying proteolytic amino acid fertilizer were higher than those of the control, while the content of total acid was lower than that of the control. Among them, the content of total sugar, soluble solids and vitamin C was 16.1%, 15.1% and 18.1% higher than that of the control when the amino acid fertilizer was sprayed on the citrus at the time of 2/3 of citrus flowers withered.

Protein hydrolysates (PHs) are a kind of biostimulant products. They are called amino acid fertilizers because of their high amino acid content. The types of amino acids obtained by plant proteolysis are closer to the amino acid spectrum of plants and are easily absorbed by plants. It has higher activity and is safer to use. In recent years, the application of amino acid fertilizers in field crops, fruits, vegetables and other crops has become increasingly common.

Proteolytic amino acid fertilizer has all the properties of farmyard manure, chemical fertilizer, plant growth conditioner and plant nutrition promoter. It is an organic fertilizer that can replace some chemical fertilizers. It is of great significance for reducing chemical fertilizer application and producing citrus safely. In addition, proteolytic amino acid fertilizers can help plants survive harsh weather such as hot, cold, and drought, and provide nutritional support at critical stages of plant growth, which is an ideal supplement to traditional fertilization.