TWO WITHIN-FIELD RAINWATER HARVESTING MEASURES AND THEIR EFFECTS ON INCREASING SOIL MOISTURE AND CROP PRODUCTION IN NORTH CHINA ABSTRACT INTRODUCTION

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1 TWO WITHIN-FIELD RAINWATER HARVESTING MEASURES AND THEIR EFFECTS ON INCREASING SOIL MOISTURE AND CROP PRODUCTION IN NORTH CHINA Jianxin Zhang 1,2, Dawei Zheng 1, Yantian Wang 1, Yu Duan 3, Yanhua Su 1 (1.College of Resources and Environment, China Agricultural University, Beijing, China, 194; 2.Shanxi Meteorological Bureau, Taiyuan, China, 32; 3. Agricultural Institute of Inner Mongolia Autonomous Region, Huhehaote, China, 13) ABSTRACT Two within-field rainwater harvesting measures are introduced in this paper. The first one is called gradually constructed, the second one is called planting. The experiment shows that soil moistures under the two measures are observably higher than that of the after all types of rain (moderate or light rain; heavy rain) and under long rainless condition. But if a heavy rain comes soon after several anterior heavy rains, then effects of the two measures on harvesting rain and increasing soil moisture will be less obvious. These two measures also have obvious effects on increasing crop production, the planting can increase crop production by 74.2%, and gradually constructed can increase crop production by 37.1%. Key Words: Rainwater harvesting, Gradually constructed, Contour ridge and furrow planting, Soil moisture, Crop production INTRODUCTION Rainwater harvesting has a history of thousands of years in the world (Evenari, Shanan, Tadmor & Aharoni, 1961; Zhao,1996; Wesemael et al.,1998; Scott & Silva-Ochoa, 21). It has become an effective way to fight against droughts for arid and semi-arid region. There are many types of rainwater harvesting (Boers & Ben-Asher, 1982; Critchley & Siegert,1991; Oweis et al.,1999; Abu-Zreig et al.,2; Li et al.,22), but to the sloping field of hilly area, microcatchment rainwater harvesting especially within-field rainwater harvesting is more useful because it s simple, cheap, efficient and adaptable. In this study, we introduce two new microcatchment rainwater harvesting measures.º' C MATERIALS AND METHODS Study site description The study is conducted at the Rainwater Harvesting Experimental Station of China's Water Conservancy Ministry in Zhungeer County, Inner Mongolia Autonomous Region in 24. The station is located at the north of Loess Plateau(39º34'N, 11º42'E, elev. 132m) where the climate is temperate and semi-arid: the mean annual temperature is 7.2ºC, January is the coldest month with mean temperature -12.9ºC, July is the hottest month with mean temperature 24.8ºC; the mean annual precipitation is 397.1mm, 6~7 percent of which falls from July to September; the annual pan evaporation is 293mm, about 5 times of the precipitation. The soil texture here is sandy loam (sand: 65.4%, silt: 3.9%, clay: 3.7%); its bulk density is 1.22g/cm 3.

2 Measures description Two within-field rainwater harvesting measures are set in the experiment. The first one is called gradually constructed. The second one is called planting. Gradually constructed Contour terrace is a very useful way to retain runoff and prevent water & soil loss, but the traditional method of constructing level terrace needs a lot of manpower, material and resource, and it takes a long time (usually more than 3 years) for the soil fertility to recover and become feasible for planting, so the crop yield will decrease after construction. Gradually constructed is a completely new kind of, which is an innovative combination of contour planting, one direction ploughing and terrace constructing techniques, it also saves labor and doesn't reduce crop yield. Therefore, it's applicable in the arid hilly areas where the economic condition is not good, the input to agriculture is greatly limited and there is much more farm land for every householder than that in other areas. The key points of making gradually constructed are: (1) to line out several contours according to the slope condition, usually 1m altitude difference between two contours; (2) to build ridges of field about 5cm high on the contours; (3) to use bi-directional plough to till the slope land from the higher side to the lower side along contours every year. Each year 15~2cm deep soil is turned from the higher side to the lower side, 2~3 years later, the slope field with 1m altitude difference will be gradually turned into a level terrace. In this study, the sketch of making gradually constructed is as figure 1: building ridges first tilth result of first tilth second tilth result of second tilth Figure 1 The sketch of making gradually constructed Contour ridge and furrow planting Contour ridge and furrow planting technique combines cultivating technique and water conservative means perfectly. The key technical points and operational ways are showed in figure 2. topsoil ridge slope (1) (2) (3) (4) Scarifying ridge (5) (6)Scarifying (7) Figure 2 The sketch of making (1) Digging up the topsoil and putting it aside. (2) Using the deep soil to build first ridge and make the first furrow passingly. (3) Scarifying the deeper soil of the first furrow. (4) Putting the topsoil into the first furrow and repeating step (1). (5) Repeating step (2), and building the second ridge. (6) Repeating step (3).

3 (7) Repeating step (4) and continuing From figure 2, we can see this measure not only can retain runoff, but also can improve the soil. In this study, furrow width is 4~45cm, ridge width is 35~4cm, ridge height is 2cm. Seeds are sowed in furrows. Experiment design Gradually constructed Contour ridge and furrow planting Control Figure 3 Arrangement of the experiment Experiment arrangement We set the above two measures and a area in the experiment, they are arranged as figure 3 Broom-corn millet(panicum miliaceum L.) was chosen as the experimental crop in 24, its varietal name is Yushu No.1. We used drilling method to plant it, the row spacing was 2cm, the planting date was May 17,24. Observing items and observing time Soil moisture Gradually constructed : Selectting an observing belt (the area between two ridges), taking two sites along vertical direction of the contour ridge(one at the higher side and another one at the lower side), observing soil moisture of ~1cm, 1~2 cm, 2~3 cm, 3~4 cm and 4~5cm depths respectively every ten days from seeding to harvest, 3 repetition. Contour ridge and furrow planting field: Observing soil moisture of ~1cm, 1~2 cm, 2~3 cm, 3~4 cm and 4~5cm depths of a furrow every ten days from seeding to harvest, 3 repetition. Control area: Observing soil moisture of ~1cm, 1~2 cm, 2~3 cm, 3~4 cm and 4~5cm depths every ten days from seeding to harvest, 3 repetition. Crop growth and yield Observing crop height, ears length, density at heading stage; Observing biologic mass at jointing and heading stage respectively, Observing yield at harvest stage. RESULTS AND DISCUSSION Effects of harvesting rain and increasing soil moisture Under moderate or light rain condition Figure 4 shows the soil moisture on June 7,24. Before this day, there was a rainfall of 12.4mm on May 27, between May 28 and June 4 there was no rain, there was another rainfall of 11.7mm on June 5. From the figure we can see:

4 Soil Moisture(%) low site of gradually constructed high site of gradually constructed Figure 4 Effect of the two measures on harvesting rain and increasing soil moisture under moderate or light rain (June 7,24) (1) The two measures all have obvious effects on harvesting rain and increasing soil moisture, especially below 1cm. At depth 2~3cm, soil moisture of field is 3.3 percent points higher than that of the, and soil moisture of the low site of gradually constructed contour terrace is 2.1 percent points higher than that of the. (2) Soil moisture of the high site of gradually constructed is also higher than that of the, it is because the gradually constructed has been ploughed once from high to low, the slope becomes smaller than that of the. (3) At the depth ~1cm, there is little difference among the two measures and the. Under long rainless condition Figure 5 gives the soil moisture on July 7,24. There was only 7.7mm rainfall from June 7 to July 7, soil moisture decreased greatly. From the figure we can see: Soil Moisture(%) low site of gradually costructed high site of gradually constructed Figure 5 Effects of the two measures in harvesting rain and increasing soil moisture under long rainless condition (July 7,24) (1) Because of the long rainless time, at the depth ~1cm, soil moisture of the two measures and the had been very low, they were all under 8.6%. (2) Below 1cm, effects of the two measures on harvesting rain and increasing soil moisture began to emerge. At depth 2~3cm, soil moisture of field is 4.6 percent points higher than that of the, soil moisture of the low site of gradually constructed is 4.8 percent points higher, and soil moisture of the high site of gradually constructed is also 3.7 percent points higher than that of. The effects are very obvious.

5 Under heavy rain condition There was a 32.3mm rainfall on July 23, soil moisture on July 24 is showed in figure 6. We can see: Soil Moisture(%) low site of gradually costructed high site of gradually constructed Figure 6 Effects of the two measures on harvesting rain and increasing soil moisture under heavy rain condition (July 24,24) (1) After heavy rain, the two measures all have very prominent effects on harvesting rain and increasing soil moisture. At depth 2~3cm, soil moisture of field is 2.7 percent points higher than that of the, soil moisture of the low site of gradually constructed is 8.1 percent points higher, and soil moisture of the high site is also 2.4 percent points higher. (2) Contrasting the two measures, because there was a lot of runoff collected and infiltrating in the low site of gradually constructed, soil moisture of the low site of gradually constructed is higher than that of planting field at each depth. If a heavy rain comes soon after several anterior heavy rains, then effects of the two measures on harvesting rain and increasing soil moisture will be less obvious. This is because with frequent and big rainfalls, infiltration of the field also increases observably, and owing to the soil under the two measures close to saturation, the increase of soil moisture will be limited. For example, after rainfall on July 23, there were 24.2mm rainfall on July 25~26 and 3.7mm rainfall on July 29. Soil moisture on July 3 can prove the above viewpoints (Figure 7) Soil Moisture(%) low site of gradually constructed high site of gradually constructed Figure 7 Effects of the two measures on harvesting rain and increasing soil moisture after heavy rain on July 29 (July 3,24) There was a storm rainfall of 14mm on August 1, soil moisture was observed on August 11. The result is given in figure 8, we can see that soil moisture difference between the two measures and the is quite limited.

6 Soil Moisture(%) low site of gradually constructed high site of gradually constructed Figure 8 Effects of the two measures on harvesting rain and increasing soil moisture after storm rainfall on August 1 (August 11,24) Effects on promoting crop growth and increasing crop production On July 2 and August 18,24, dry biologic mass of Broom-corn millet was measured (Table 1). Table 1 Dry biologic mass of Broom-corn millet under the two measures and the Measures Observing Date Stem Weight of an Individual Plant(g) Root Weight of an Individual Plant(g) Weight of an Individual Plant(g) Contour ridge and furrow July planting August Low site of gradually constructed contour terrace High site of gradually constructed contour terrace Control July August July August July August Note: Taking 1 individual plants continuously for each measure, dividing individual plant into stem and root. Weighing them after drying. Finally taking the average value On August 23,24, height, ear length and density of Broom-corn millet were measured ( Table 2). Table 2 Broom-corn millet s growth situation under the two measures and the Measures Height(cm) Ear Length(cm) Density(stems/m 2 ) Contour ridge and furrow planting Low site of gradually constructed contour terrace High site of gradually constructed contour terrace Control Note: Taking 1 individual plants continuously for each measure in height and ear length observation and use the average value of 1 individual plants; Taking 1 m 2 for each measure in density

7 observation and counting the stems. On October 13,24, we observed the production ( Table 3): Table 3 Broom-corn millet s output under the two measures and the Measures Output (g/ m 2 ) Contour ridge and furrow planting Gradually constructed Control Note: Taking 1 m 2 for each measure, weighing up the grain output. From the above 3 tables, we can see that there is obvious difference in every aspect of crop growth and production between the two measures and the. CONCLUSIONS Agricultural production of dry land farming in the semi-arid regions of China is much dependent on rainfall and its distribution. Frequent drought is the main factor limiting crop yield. Water harvesting is an effective way to mitigate drought. From the above experimental results, we can obtain the following conclusions: (1) The two measures planting and gradually constructed all can intercept runoff, collect rainwater, thus increase soil moisture. (2) Due to the improvement of soil moisture condition, the two measures all have obvious effects on promoting crop growth and increasing crop production. (3) Contrasting the two measures, we recommend gradually constructed. Although its effects on increasing crop production is not as good as planting in this experiment, but it is a long-term measure. Because several years after the implementation, the slope field will be turned into level terrace, soil erosion will be reduced greatly. The effects on improving soil moisture and fertility will be more and more obvious. ACKNOWLEDGEMENTS This study is financially supported by the project of Chinese national high technological research development plan The synthetical rainwater harvesting techniques study and demonstration in north China. The authors would like to thank professor Lin-Qimei and professor Tuo-Debao for their suggestions in the experiment design. We also give thanks to Mr. Fu-Guisuo and Mr. Ma-Zhiguo for their assistance in the observational work. REFERENCES Abu-Zreig,M.,Attom,M.&Hamasha,N., 2. Rainfall harvesting using sand ditches in Jordan. Agricultural Water Management[J], 46: Boers,Th.M.&Ben-Asher,J A Review of Rainwater Harvesting. Agricultural Water Management[J], 5: Critchley, W., Siegert, K., Water harvesting: a manual for the design and construction of water harvesting schemes for plant production. FAO, Rome, Available from Evenari,M.,Shanan,L.,Tadmor,N.&Aharoni,Y.,1961. Ancient agriculture in the Negev. Science, 133(3457): Li,X.Y.,Gong,J.D.,22. Effects of different ridge:furrow ratios and supplemental irrigation on crop production in ridge and furrow rainfall harvesting system with mulches. Agricultural Water Management [J], 54:

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