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UDC 635.655:631.5
THE IMPACT OF DESICCANTS AND GROWTH REGULATORS ON THE SOWING QUALITY OF SOYA SEEDS
Durnev G.I., Doctor of Agricultural Sciences Yatchuk P.V., Post-graduate student Orel State Agrarian University, Orel City, Russia E-mail: crop-science@orelsau.ru
ABSTRACT
The text under review deals with the results of studies of the technological parameters of using desiccants Reglon Super and RAP-600 on yield and sowing quality of soya seeds in the Orel region. Additionally the impact of growth stimulating preparations on the stressful situation of desiccants on seed germination and the residual amount of pesticides were determined.
KEY WORDS
Soya; Desiccants; Yield; Moisture; Quality; Seeds.
Soya is practically a new culture for the Orel region. Its crops have been increased rapidly for the last decade thanks to the fruitful work of the local plant breeders, who have bred early-ripening varieties, the seeds yield of which is harvested at the end of August and in the middle of September, using the sum of positive temperatures in the region 1900 -2300°C. To obtain high yields of high quality seeds soya is harvested in the first days of beans maturation. In the wet years soya matures long and uneven. In this case, a preharvesting crop desiccation (drying) with Reglon Super and other preparations is used when seeds moisture is 35-40% [3].
By now the world has accumulated a wide experience of desiccants application on the seed crops of various agricultural crops. However, the analysis of their application leads to the contradictory conclusions. Desiccation is established to accelerate the process of seeds maturing for 10-12 days, to ensure its steady character, to reduce damage and affection by fungal diseases, to increase dramatically the productivity of mechanized harvest [5, 9].
It has practically no influence on seed productivity, biochemical and biological properties of seeds, and in some cases even improves them [8]. There hasn't been enough research of this kind on soya.
METHODOLOGY AND OBJECTS FOR RESEARCH
Laboratory and field experiments are being carried out on the experimental field and in the laboratory for seed studies and primary seed breeding of the All-Russian Research Institute for Leguminous Crops in 2011-2013. The experimental plot has dark gray forest soil. The humus content is 4.5%, P2O5 - 12, K2O - 11 mg/100 g of the soil, pH - 5,2. The power of humus horizon is 30 cm. The object for research is soya variety Lantsetnaya, desiccants are Reglon Super and RAP- 600.
The field experiments are carried out on the test plots of 10 m2 in fourfold replication. The location of the test plots is randomized. In 2011 the sowing was done on the 21-st of May and in 2012 - on the 17-th of May with the selective drill SCS - 6-10, the planting distance was 45 cm wide. The seeding rate of the viable soya seeds is 0.6 million seeds per hectare. The background of mineral fertilizers is N30Р45К45. The treatment of the crops with desiccants was conducted in 3 periods.
The rate of working solution discharge was determined on the basis of 300 l/ha. The plants were sprayed with pneumatic manual sprayer OP - 1.5 in windless dry weather. In 2011 desiccants started to be used on the 21-st of August when seeds moisture reached
50%. The soya leaves turned yellow and began to fall down at the foot end, beans and seeds began to turn yellow.
In 2012, the first treatment with desiccants started on the 11-th of August when seeds moisture reached 65 % (the beginning of yellowing of the foot leaves of the soya plants), i.e. as soon as the visible sign appeared. The rate of desiccants application is for Reglon - 1,5; 2,0; 2,5 l/ha, for RAP - 600 - 2,0; 2,5; 3,0 l/ha.
THE RESULTS OF THE RESEARCH
It should be noted that the weather conditions in 2011 and 2012 were alike: the first half of the vegetation period had a lack of moisture but excessive heat, the second half - the excessive moisture and moderate heat.
Both years were generally favorable for the growth and development of soya. One of the main research indicators of the impact of desiccants on soya plants was the seeds moisture. The analysis of soya seeds moisture dynamics in 2011 showed that both preparations Reglon and RAP 600 caused the decrease of plants moisture . The effect of Reglon was more efficient due to its different preparative forms (Fig.1).
■ 21.08.2011 ■ 26.08.2011 ■ 31.08.2011 - 11.08.2012 - 19.08.2012 27.08.2012
Control Region 2,0 l/ha RAP-600 2,5 l/ha
Figure 1 - Soya seeds moisture after treatment with Reglon Super and RAP-600
The desiccants had slight effect on the yield of soya seeds during all periods, even at their early application - in the beginning of yellowing of the foot leaves (Table 1).
The use of desiccants in the first period in 2011 decreased the seed yield by 5 - 10%. This period coincided with the seeds color changing from green to yellow and with leaves turning yellow on the whole plant. Seeds moisture reached 48 - 50%. In the next periods of application desiccants practically did not decrease yields in comparison with the control. The differences in decreasing were more frequent within the experimental error.
It should be noted that in 2012 preparations started to be applied in the earliest period when it only can be visually detected - at the beginning of yellowing of the foot leaves. It didn't make any influence on the soya seeds. It was close to the control. Unlike 2011, soya yield in 2012 was higher when being treated with Reglon by 0.4-1.0 cwt/ha, with RAP - 600 by 1.9 - 2.6 cwt/ha. Thus, our data disprove the generally accepted recommendations that desiccants need to be applied when beans in the foot and middle parts turn brown and soya seeds moisture reaches 45 % [7].
Table 1 - The yield of soya seeds depending on the time and rates of the desiccants application
(cwt/ha)
Variants Time of application Average h/ha
I II 1 III
21.08.11 11.08.12 26.08.11 19.08.12 31.08.11 21.08.12 2011 2012
Control 21,0 21,6 21,4 22,0 21,4 21,7 21,3 21,8
Rec lon Super
1,5 l/ha 19,8 20,9 21,2 21,4 21,3 21,4 20,8 21,2
2,0 l/ha 19,4 20,4 20,1 20,8 20,0 21,1 19,8 20,8
2,5 l/ha 19,1 20,6 19,2 20,2 20,3 20,7 19,5 20,4
HCPo,5 1,2 0,3 1,1 0,3 0,7 0,8
RAP - 600
2,0 l/ha 19,1 21,6 19,4 21,7 20,7 21,4 19,7 21,6
2,5 l/ha 18,7 21,4 18,9 21,5 19,0 21,6 18,9 21,5
3,0 l/ha 18,3 21,2 18.6 21,4 19,0 20,7 18,6 21,1
HCP05 0,8 0,5 1,1 0,4 1,6 0,4
The accumulation of fat and protein in soya seeds, according to many authors [4, 5], goes on until their maturity. The use of desiccants in our research reduced the protein and fat content, especially with the increase of the norms of preparation discharge. But the difference was within the experimental error (Table. 2).
Table 2 - The impact of desiccants on the soya seeds quality
Variants Time of application
21.08.11 11.08.12 26.08.11 19.08.12 31.08.11 21.08.12
Protein, %
Control 36,2 40,1 36,1 40,4 36,2 39,8
1,5 l/ha 36,9 39,6 36,6 40,1 36,1 39,7
Reglon Super 2,0 l/ha 36,6 39,9 36,8 40,5 36,7 39,9
2,5 l/ha 35,6 38,2 38,2 39,8 37,3 38,4
2,0 l/ha 35,0 39,8 36,0 40,2 36,0 40,4
RAP- 600 2,5 l/ha 34,3 39,7 35,5 39,9 36,0 40.4
3,0 l/ha 34,0 38,6 35,0 39,8 35,8 40,2
Oil, %
Control 23,3 21,6 23,6 21,9 23,3 22,2
1,5 l/ha 23,2 20,0 23,5 21,8 23,6 21,9
Reglon Super 2,0 l/ha 23,1 20,7 23,2 20,0 23,4 22,0
2,5 l/ha 22,9 20,5 22,6 22,0 23,0 21,7
2,0 l/ha 22,8 21,4 23,2 21,9 23,5 22,0
RAP - 600 2,5 l/ha 22,7 21,2 23,2 21,8 23,1 21,8
3,0 l/ha 22,5 21,0 22,7 21,8 22,1 21,0
The desiccation when seed moisture is 50 % in the first period of treatment of variety Lantsetnaya in 2011 caused a slight decrease in protein content. When treating with Reglon the reduction of protein content was obtained at the rate of 2.5 l/ha (0.6%). In other variants, there was an increase of protein by 0.3 and 0.6 % in comparison with the control.
The effect of RAP -600 consisted in the considerable reduction of protein content from 1.2 % to 2.2 % when keeping it under control at 36.2%. Its maximum content was obtained with variant Reglon 2.5 l/ha and reached 38.2 %. The oil content in the samples studied ranged from low - 22,6 %, up to medium - 23,2 % depending on the time of treating with desiccants. Its maximum was obtained when plants were treated with Reglon at the rate of 1.5 l/ha in the third period of treating - 23.6 percent.
In 2012 the desiccation carried out in the earlier period practically had no impact on the decrease of protein and oil in the soya seeds. Their indicators were at the same level as the control [2]. In this case, it is necessary to point out the tendency of protein content increase and oil content decrease, in comparison with the year 2011, in variants with Reglon and RAP - 600.
With the physiological ripeness of seeds the laboratory tests for their sowing quality were carried out, as well as for their response to growth-stimulating preparations. The results
of the analyses are shown in Table 3. On average for two years period the germination energy of soya seeds after treatment with desiccation preparations has reached in the variants of experiment 65-73%, when the control was 63%.
Table 3 - The impact of desiccants and growth stimulating preparations on sowing
quality of soya seeds
Variants of experiment 2011 2012
Aqua Binoram Potassium Aqua Binoram Potassium
Destillata ZH Humate Destillata ZH Humate
Germination energy, %
Control 66 93 83 60 71 77
Region Super, l/ha 1,5 62 80 76 67 73 80
2,0 71 99 81 69 80 88
2,5 74 97 80 72 83 86
RAP- 600, l/ha 2,0 70 86 81 71 87 92
2,5 67 83 80 68 90 93
3,0 70 88 81 74 87 95
Germination index, %
Control 95 97 96 90 92 95
Region Super, l/ha 1,5 99 95 97 96 96 98
2,0 97 99 95 98 98 99
2,5 95 99 97 99 99 99
RAP- 600, l/ha 2,0 97 98 96 87 90 96
2,5 99 99 97 90 92 98
3,0 97 98 98 82 91 97
The desiccation of soya crops has not influenced such an important indicator of quality of seed as laboratory germination. According to the results of two-year old data it can be seen that the laboratory germination of soya seeds in the variants of experience ranged from 90 to 99 % when the control was 93%. The highest values of germination energy and laboratory germination are obtained from Binoram and potassium Humate. These preparations significantly stimulated the indicators analyzed, especially germination energy. When being treated with them, the germination energy increased by 12-17% , the germination of seeds - by 1-5%. The stimulating difference between Binoram and Potassium Humate has not been found out.
According to the environmental requirements the seeds at the permissible content of DDT and HCH can be used either as a seed material or for technical purposes [1]. When the content of these poisons slightly exceeds the maximum permissible limits, the seeds can be mixed with seeds free from them, on condition of bringing the residual amount of the preparation to the permissible quantity [6]. The results of the determination of residual concentrations of desiccants in soya seeds are given in Table 4.
Table 4 - The residual content of pesticides in the soya seeds
Permissible Concentration Control Found
Pesticides (without Region RAP - 600
desiccation) 1,5 l/ha 2,5 l/ha 2,0 l/ha 3,0 l/ha
HCH,mg/kg Not more than 0,5 Not more than 0,03 Not more than 0,02 Not more than 0,02 Not more than 0,01 Not more than 0,03
DDT Not more than 0,05 Not more than Not more Not more Not more Not more
mg/kg, 0,004 than 0,001 than 0,003 than 0,002 than 0,002
From the data above we can conclude that after the treatment of soybean with Reglon Super and RAP - 600 the residual content of pesticides, namely a, p, y isomers of HCH and DDT and its metabolites has not exceeded the rate according to the Government Standard. Therefore the harvest obtained can be used both as a sowing material, and in industry.
CONCLUSION
Our studies have revealed that desiccants can be used much earlier, not when seeds moisture is 45 %, but when it is 65 %. According to the results of two-year studies there was a tendency of slight decrease of the protein content and increase of the oil content in variants with desiccation in 2011, and in 2012 - vice-versa. The preharvest desiccation carried out both in the early and later periods, did not worsen the laboratory germination. This indication ranged, depending on the preparation, from 90 to 99%, which meets the requirements of the Government Standard for original seeds. The residual content of pesticides did not exceed the rate of the Government Standard.
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