|Abstract|

Using ryegrass as the test material, the 32-tray plug tray matrix culture method was used to study the effects of the planting rates (7, 14 grains/tray) on the three harvests of ryegrass cultivated with LED white light (the 17th, 34th, 51 days) impact on yield. The results show that ryegrass can grow normally under the white light LED, and the regeneration speed is fast after cutting, and it can be produced according to multiple harvesting methods. The seeding rate had a significant effect on the yield. During the three cuttings, the yield of 14 grains/tray was higher than that of 7 grains/tray. The yields of the two seeding rates showed a trend of first decreasing and then increasing. The total yields of 7 grains/tray and 14 grains/tray were 11.11 and 15.51 kg/㎡, respectively, and they have the potential for commercial application.

Materials and Methods

Test Materials and Methods

The temperature in the plant factory was 24±2 °C, the relative humidity was 35%–50%, and the CO2 concentration was 500±50 μmol/mol. A white LED panel light with a size of 49 cm×49 cm was used for illumination, and the panel light was placed 40 cm above the plug tray. The ratio of the matrix is peat: perlite: vermiculite = 3:1:1, add distilled water to mix evenly, adjust the water content to 55%~60%, and store it for 2~3 hours after the matrix fully absorbs water and then evenly install it in 54 cm × 28 cm in a 32-hole plug. Choose seeds that are plump and uniform in size for sowing.

Test Design

The light intensity of the white LED is set to 350 μmol/(㎡/s), the spectral distribution is as shown in the figure, the light-dark period is 16 h/8 h, and the light period is 5:00~21:00. Two seeding densities of 7 and 14 grains/hole were set for sowing. In this experiment, the seeds were sown on November 2, 2021. After sowing, they were cultivated in the dark. Lighting was started on November 5. During the light cultivation period, Hoagland nutrient solution was added to the seedling tray. 

Spectrum for LED white light

Harvest Indicators and Methods

Observing that when the average height of the plants reaches the height of the panel light, harvest it. They were cut on November 22, December 9 and December 26, respectively, with an interval of 17 days. The stubble height was 2.5±0.5 cm, and plants were randomly selected in 3 holes during harvesting, and the harvested ryegrass were weighed and recorded, and the yield per square meter was calculated in formula (1). Yield, W is the cumulative fresh weight of each cutting stubble.

Yield=(W×32)/0.1512/1000(kg/㎡)

(Plate area=0.54×0.28=0.1512 ㎡) (1)

Results and Analysis  

In terms of average yield, the yield trends of the two planting densities were the first crop > the third crop > the second crop, 24.7 g > 15.41 g > 12.35 g (7 grains/hole), 36.6 g > 19.72 g, respectively. ＞16.98 g (14 capsules/hole). There were significant differences between the two planting densities in the yield of the first crop, but no significant difference between the second, third crop and total yield. 

Effects of sowing rate and stubble cutting times on ryegrass yield

According to different cutting plans, the production cycle is calculated. One cutting cycle is 20 days; two cuttings are 37 days; and three cuttings are 54 days. The seeding rate of 7 grains/hole had the lowest yield, only 5.23 kg/㎡. When the seeding rate was 14 grains/hole, the cumulative yield of 3 cuttings was 15.51 kg/㎡, which was about 3 times the yield of 7 grains/hole cutting 1 time, and was significantly higher than other cutting times. he length of the growth cycle of three cuts was 2.7 times that of one cut, but the yield was only about 2 times that of one cut. There was no significant difference in the yield when the seeding rate was 7 grains/hole cutting 3 times and 14 grains/hole cutting 2 times, but the production cycle difference between the two methods was 17 days. When the seeding rate was 14 grains/hole cut once, the yield was not significantly different from that of 7 grains/hole cut once or twice. 

Yield of ryegrass mowed 1-3 times under two seeding rates 

In production, a reasonable number of shelves, shelf height, and seeding rate should be designed to increase yield per unit area, and timely mowing should be combined with nutritional quality evaluation to improve product quality. Economic costs such as seeds, labor, and fresh grass storage should also be considered. At present, the pasture industry is also faced with the problems of an imperfect product circulation system and low commercialization level. It can only be circulated in local areas, which is not conducive to realizing the combination of grass and livestock across the country. Plant factory production can not only shorten the harvest cycle of ryegrass, improve the output rate per unit area, and achieve annual supply of fresh grass, but also can build factories according to the geographical distribution and industrial scale of animal husbandry, reducing logistics costs.

Summary

To sum up, it is feasible to produce ryegrass under the LED lighting fixture. The yields of 7 grains/hole and 14 grains/hole were both higher than those of the first crop, showing the same trend of first decreasing and then increasing. The yields of the two seeding rates reached 11.11 kg/㎡ and 15.51 kg/㎡ at 54 days. Therefore, the production of ryegrass in plant factories has potential for commercial application.

Author: Yanqi Chen, Wenke Liu.

Citation information:

Yanqi Chen, Wenke Liu. Effect of seeding rate on ryegrass yield under LED white light[J]. Agricultural Engineering Technology, 2022, 42(4): 26-28.