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K. Ozawa
Tohoku National Agricultural Experiment Station, Morioka,
Iwate 020-0123, Japan
tion, Morioka, Iwate 020-0123, Japan
T. Luo
Xinjiang Institute of Biology, Pedology and Desert Research, Chinese
Academy of Sciences, Urumqi, Xinjiang 830011, China
A passive production technique implies that little or no artificial
energy is needed. We developed two passive techniques: furrow
bottom seeding and foliar water spraying. The furrow bottom seeding
conserves soil water and decreases soil temperature. The foliar
water spraying reduces plant water stress and promotes root growth.
These two techniques enabled crop production with a reduction
of irrigation water in arid regions at a lower cost of operation.
Key words: Brassica campestris var. Komatsuna, foliar water spraying,
furrow bottom seeding, salinity, soil temperature, soil water,
water saving, wheat
High-tech crop production practices are not practical in developing countries because it is too costly for growers. These growers seldom have electric power in their fields or greenhouses. Instead of expensive technology, cheaper, simpler, and more reasonable techniques are required in these areas. An idea called 'passive technique' was introduced in 1975 in Japan. The idea uses natural phenomena with a minimum of artificial energy. The phenomena include biological, physical and chemical characteristics of plants, soils, materal, physical and chemical characteristics of plants, soils, materials, and equipment (Hoshiba and Ozawa, 1994). The techniques conducted from the idea are usually inexpensive and simple.
In this paper, we introduce two passive techniques: furrow bottom seeding and foliar water spraying. These techniques enabled crop production with reduced amounts of irrigation water on an oasis farm in Xinjiang, China, where a large amount of water has been used for crop production in spite of limited water resources.
The experiments were conducted in the Fukan Desert Ecosystem Observation
and Experiment Station of the Xinjiang Chinese Academy of Sciences
in the summers of 1995 and 1997. The station is in XinJiang Uygur
Autonomous Region, the inland area of middle Asia. It is at the
northern foot of the Tienshan Mountains and the southern border
of the Kurbantonkut desert in the Zhungel basin. Annual precipitation
is 164 mm and annual potential evaporation is approximately 2000
mm at the station (Jiang, and Li, 1990).
The technique is the sowing of seeds at the bottom of V-shaped
furrows. Each furrow is approximately 5 cm deep. We therefore,
call this technique 'furrow bottom seeding (Ozawa and Okada, 1996).
The effects of furrow bottom seeding (FBS) were evaluated in
Xinjiang.
Te
Ten days after irrigating, seeds of Komatsuna(Brassica campestris)
'Seisen No. 7' were sown in four treatments on June 15, 1997 as
shown in Fig. 1. The plowed soil contained approximately 20%
water by dry weight at seeding time. Each treatment had three
seeding strips of one m long, 15 cm apart, with 16 seeds sown
in each strip. In treatment 1, seeds were sown in flat soil conventionally
(CS), without watering. In treatment 2, seeds were sown in the
bottoms of soil furrows 5 cm deep (FBS), without watering. In
treatments 3 and 4, seeds were sown in the CS and FBS respectively,
followed by the application of 100 mm of water by flood irrigation.
In the experiment, rows and furrows were in the east-west direction.
Soils from the surface to 5 cm deep at the seed position in each
treatment were sampled on June 21 and 28. Water content by dry
weight and electric conductivity (E.C.) were measured. Seed germination
in each treatment was recorded on June 28. Soil temperatures
at 5 cm deep below the seeded position in treatments 1 and 3 were
measured during 3 days from June 26 to 28.
As shown in Table 1, the seed germination rates and leaf areas
in the watered treatments were lower than in the FBS due to the
soil surface crusting. Both responses were the highest in FBS
without watering. Soil water content in CS without watering was
less than those of the otheout watering was
less than those of the other treatments. As shown in Figure 2,
the soil temperature at a depth of 5 cm varied daily, highest
at about 16:00, and lowest at about 6:00. In the CS, the maximum
soil temperature was 34¡ C and the minimum was 20 ¡C.
In the FBS, the maximum temperature decreased by 5¡ C, the
minimum increased by 2 ¡C, and the mean decreased by 1 ¡C
compared with the temperatures in the CS. The E.C. values on
June 28 were highest at furrow ridge, followed by these in the
CS. Those in the furrow bottoms were lowest as shown in Table
2. The value just after seeding was 0.83.
The field was divided into plots with five rates of irrigation:
5 mm, 10 mm, 15 mm, 25 mm and 50 mm. Wheat(Triticum aestivum)
'Shidong No. 5' and Komatsuna 'Seisen No. 7' were sown in those
plots in the CS and the FBS on Aug. 30, 1997, two days after watering.
One hundred wheat seeds and 72 Komatsuna seeds were sown in rows
and furrow bottoms 25 cm apart. The distance between seeds was
6 cm for wheat and 5 cm for Komatsuna. Plant upper fresh weights
were measured on Sept. 28.
As shown in Fig. 3, the fresh weight per unit area increased with
increasing irrigation rates. The fresh weight of wheat in the
CS with 50 mm watered was similar to the fresh weight in the FB0 mm watered was similar to the fresh weight in the FBS
with 25 mm of water. The fresh weight of Komatsuna in the CS
with 50 mm water was similar as that in the FBS with 15 mm water.
Loss of soil water was reduced in the FBS due to two factors: (1) the ridges served as a windbreak and decreased evaporation from the bottoms of the furrows, and (2) the sub-soil water transferred rapidly to the soil below the furrow bottoms. The maximum and minimum temperatures decreased and increased in the FBS respectively because the amplitude of daily soil temperature variation decreased in the FBS. The mean soil temperature decreased in the FBS also. We assume two causes to explain the decrease. One is that the heat exchange between soil and air accelerated due to the greater soil surface exposure in the FBS. The other is that the lower temperature in sub-soil affected the surface soil in the FBS more than that in the CS.
The FBS decreased irrigation water by 25 mm in wheat and 35 mm
in Komatsuna during the first month after sowing. The results
show that a great deal of irrigation water can be saved. We have
developed a manually operated and cheaper FBS machine (Figure
4). Cylindrical land rollers of a conventional seeding machine
were changed to 'abacus bead' shaped rollers (Ozawa and Okada,
1996). The FBS technique is useful in saline soils, frequent
in arid regions, because the FBS delaysoils, frequent
in arid regions, because the FBS delays salinity accumulation.
In this technique, a small quantity of water is sprayed on leaves
at dusk for a few days after transplanting to reduce plant water
stress. Effects of the technique were evaluated in Xinjiang.
Sweet potato and cabbage transplants were planted in a field
soil with 20% water on June 14, 1995. Six plants of each crop
were divided into 3 treatments. In treatment 1, plants were un-sprayed
with less watering. In treatment 2, sprayed with less watering.
In treatment 3, un sprayed with conventional watering. In treatment
3, approximately 100 mm of water was flooded just after transplanting.
In treatments 1 and 2, 2 liters of water were supplied in the
soil surrounding each plant just after transplanting. The spot
irrigation was equivalent to a watering of 6 mm. In treatment
2, a bit of water was sprayed on leaves 4 times a day from 15:30
to 16:30 on June 15,16, 17, 19 and 20. All plants of sweet potato
and cabbage were sampled on June 27 to measure the dry weight
of leaf blades and secondary roots.
As shown in Table 3, weights of leaf blades and secondary roots
of sweet potato in treatment 2 were the highest in all treatments.
Those in treatment 3 followed, and those inl treatments.
Those in treatment 3 followed, and those in treatment 1 were
least. However, weights of leaf blades and secondary roots of
cabbage were highest in treatment 3. Those treatment 1 followed,
and those treatment 2 was least.
Tomato transplants were planted in the field on June 15, 1995.
Three plants were used in each of 3 treatments. In treatment
1, plants were un-sprayed with less watering. In treatment 2,
sprayed with less watering. In treatment 3, un-sprayed with conventional
watering. In these plots, plants were treated the same as the
former experiment. The xylem water potential of leaves in each
treatment was measured on June 21 at 6:00, 9:00, 12:30 and 15:00,
using a pressure chamber.
As shown in Figure 5, the xylem water potential of tomato leaves
in all treatments decreased with time. Treatment 1 had the lowest
xylem water potential. Treatment 3 was higher than that of treatment
2 before 12:30. However, no significant difference was found
between these two treatments after 12:30.
Generally, plant roots under water stressed conditions grow during the night when the plant water stress is reduced. The rapid reduction of water stress at dusk due to foliar water spraying advances root elongation during the night (Ozawa,r spraying advances root elongation during the night (Ozawa, 1989). The elongated roots absorb more water because the soil mass in which the roots grow increases. Then the plant water stress in the morning is also reduced even after the end of the foliar water spraying (Ozawa, 1988 and Ozawa, 1989). The increase of water absorption enables the rapid reduction of plant water stress at dusk the same as foliar water spraying. It makes well-developed plant roots for a long period. Upper plant parts grow according to roots development under water stressed condition (Ozawa, 1990). As a result, five days of foliar water spraying increased tomato yield over 30% in the summer in a sub tropical area in Japan. The yield with water spraying exceeded the yield with a large quantity of irrigation water (Ozawa, 1988).
In the experiments, five days' foliar water spraying at dusk accelerated
the growth of sweet potato transplants, and reduced water stress
of tomato transplants. Growth of these transplants was superior
to that of the conventional watered ones. The results show that
the former mechanism can be adapted to transplant production in
Xinjiang also. Foliar water spraying using manual sprayers would
increase yields, and decrease the field water used in arid regions.
However, the foliar water spraying delayed the growth of cabbage
transplants, because the leaves are less wettable than the leaves
of tomato or sweet potato. This technique is useftomato or sweet potato. This technique is useful for crops
that has wettable leaves.
A drip irrigation system, which is high-tech, is also effective
in saving a large amount of irrigation water, and controlling
salinity accumulation in arid regions. The effects of the system
would be superior to those in the passive techniques like FBS
and foliar water spraying. However, growers need much money for
investments and for running the system. Growers especially in
developing countries can adopt these passive techniques better
than the high-tech ones, because passive techniques are inexpensive
to own and operate. For the future of global horticulture, developing
and introducing passive techniques are valuable.
Hoshiba, S. and Ozawa, K., 1994, Passive systems, In: New sciences of agricultural meteorology and environment(Edited by the society of agricultural meteorology of Japan), p252-275 (Japanese).
Jiang, H. and Li, S., 1990, Soils of Fukang Desert Ecosystem Research Station and its neighbor area, Arid Zone Res. 7 (an extradition), 6-13 (Chinese).
Ozawa, K., 1988, Fruit set improvement of tomato plants by reducing plant water stress, J. Agr. Met. 44, 7-14 (Japanese with English summary).
Ozawa, K., 1989, Effect of foliar mist spraying on root elongation of tomato plants, J. Agr. Met. 45. 19-23 (Japanese with English sumf tomato plants, J. Agr. Met. 45. 19-23 (Japanese with English summary).
Ozawa, K., 1990, Effect of root expands on growth and yield of Princemelon in the Ogasawara islands, Bull. Tokyo Met. Agr. Exp. Sta. 22. 1-10 (Japanese with English summary).
Ozawa, K. and Okada, M., 1996, Furrow bottom seeding under row
cover to accelerate vegetable growth in a cold season, Acta Hort.
440, 87-92.