Effects of rainfall harvesting and mulching technologies on soil water, temperature, and maize yield in Loess Plateau region of China.
The Weibei Highlands, in the southern Loess Plateau of China, is a semi-humid agricultural area that is liable to drought. Precipitation is the major water resource used for agricultural production in the region. The annual precipitation ranges between 500 and 700mm, and >60% of precipitation falls during the monsoon months of July-September (Li et al. 2000a, 2000b). Shortages and an uneven distribution of water resources occur throughout the year and restrict crop growth (Wang et al. 2009).
Plastic film mulching can reduce water loss, regulate soil temperature (Xia et al. 1997), improve the infiltration of rainwater into the soil (Ramakrishna et al. 2006), enhance soil water retention (Ghosh et al. 2006), accelerate crop growth, and significantly increase crop yields (Romic et al. 2003; Tiwari et al. 2003; Xie et al. 2005; Ramakrishna et al. 2006; Zhou et al. 2009). However, widespread use of nonbiodegradable plastic film mulch over many years might damage the sustainability of rainfed agro-ecosystems (Acharya et al. 2005) and result in serious soil and environmental pollution (Briassoulis 2006; Scarascia-Mugnozza et al. 2006). Therefore, the development and utilisation of environmentally friendly mulching materials has received widespread attention in recent years. Biodegradable materials, which decompose in the soil, are subjected to an accelerated degradation due to the action of microorganisms such as bacteria, fungi, and algae, and mineralise into carbon dioxide or methane, water, and biomass (Schettini et al. 2007).
Liquid film is a type of polymer mixture that combines with soil particles and forms a black, solidified membrane on the soil surface after water is added and it is sprayed on the soil. This membrane can improve the heat energy status of the soil by inhibiting soil water evaporation and by absorbing more solar energy (Wang and Cai 2005). Studies of biodegradable film have mainly focussed on its material composition, biodegradability, and different varieties. There is little systematic research on the application of biodegradable film in the field.
Ridge-and-furrow rainfall harvesting systems (RFRHS) consist of alternate parallel ridges and furrows on flat land, where the ridges serve as a rainfall-harvesting zone with the furrows as a planting zone (Li et al. 2001). This system can prolong the period of water availability and enhance the production of agricultural crops by collecting water from light rain, retaining surface runoff from heavy rain, and reducing unproductive evaporation (Carter and Miller 1991; Li et al. 2000b, 2001; Tian et al. 2003; Xie et al. 2005; Zhang et al. 2007). RFRHS are considered one of the most effective water-saving agricultural practices and are widely used for various crops, e.g. maize (Zea mays L.), wheat (Triticum aestivum L.), and potatoes (Solanum tuberosum), in the semi-arid regions of China. Li et al. (2001) observed that RFRHS combined with mulching pebble, gravel, and sand in the furrows could further enhance rainwater harvest ability, therefore greatly improving crop yield and water use efficiency (WUE). However, these mulches not only need sand and gravel resources, they are also quite unsuitable for mechanised farming. Therefore, their popularity and application are restricted.
The plastic-covered ridge is a key factor in rainwater harvesting with RFRHS. There was significant rainwater harvesting when using RFRHS with a plastic-covered ridge even when the natural precipitation was <5 mm. There was, however, no effect on rainwater harvesting when the ridges were not covered by plastic (Wang et al. 2009). Moreover, Qiao et al. (2008) showed that there was no significant difference in water retention between biodegradable film and plastic film at early stages of maize growth. Biodegradable film, however, was significantly less effective than plastic film during the middle and late stages of growth due to the degradation of biodegradable film.
Therefore, in order to harvest rainwater effectively in present study, the ridges were covered with common plastic film in all RFRHS. However, furrows were mulched with common plastic film, biodegradable film, liquid film, or maize straw to further prevent soil water evaporation. We investigated the effects of different covering materials on water conservation, soil temperature change, and maize yield in RFRHS, to provide a scientific basis for improved rainwater harvesting cultivation.
Materials and methods
The experiment was conducted from 2007 to 2010 at the Heyang Dryland Farming Experimental Station, Shaanxi Province, China (35[degrees]15'N, 110[degrees]18'E; elevation 910m asl). Annual mean maximum and minimum air temperatures at the site were 40.1[degrees]C and -20.1[degrees]C and annual mean temperature was 10.5[degrees]C. Total annual sunshine was 2528h and the frost-flee period was 169-180 days. Annual mean precipitation was 550 mm, with 55% falling between July and September. Total precipitation for 2007, 2008, 2009, and 2010 was 562, 470, 500, and 515 mm, respectively, while precipitation during the maize growing seasons (April-September) was 398, 330, 379, and 391mm, respectively. Monthly precipitation distributions during the experimental period are shown in Fig. 1. The experimental field was flat. Soil at the experimental site was a silt loam with pH 8.1. In the 0-20 cm soil layer, organic matter, total nitrogen (N), phosphorus (P), and potassium (K) were 11, 1, 1, and 7g [kg.sup.-1], respectively; readily available N, P, and K were 74, 23, and 136 mg [kg.sup.-1]. The previous crop on the study site was spring maize.
Experimental design and field management
The RFRHS was built by shaping the soil surface into alternate ridges and furrows. The ridges (60 cm wide, 15 cm high) served as the rainfall-harvesting zone and the furrows (60 cm wide) the planting zone. Maize plants were sown 30 cm apart in two rows in the furrows at the base of ridges. Six treatments were used in the study. Ridges were covered with standard plastic film in all RFRHS treatments, while different furrows were mulched with standard plastic film (PP), biodegradable film (PB), maize straw (PS), liquid film (PL) (Fig. 2a), or left uncovered (P) (Fig. 2b). The conventional flat field without mulching, which is widely used by local farmers, was used as the control (CK) (Fig. 2c). Each treatment had three replicates, and each plot was 8.1 m long and 3.6m wide in a randomised arrangement.
In 2007, ridges were banked up with soil at planting time. The base fertiliser consisted of 200 kg [ha.sup.-1] of urea (N 46%), 326 kg [ha.sup.-1] of diammonium phosphate ([P.sub.2][O.sub.5] 46%, N 18%), and 333 kg [ha.sup.-1] of potassium sulfate ([K.sub.2]O 45%), which was spread evenly over the furrow and ploughed into the soil layer. Mulching was then applied to the soil surface. Ridges were covered with plastic film (PE film, 80 cm wide and 8 gm thick; Shanxi Yuncheng Plastic Plant, Shanxi, China), while the furrows of PP and PB plots were mulched, respectively, with standard plastic film and biodegradable film (Shaanxi Huayu Biological High-tech Co. Ltd, Shaanxi, China). Maize straw was cut into 15-cm-long segments and uniformly applied at a rate of 9000 kg [ha.sup.-1] in furrows with the PS treatment. Liquid film (Beijing Jinshanghe Bio-tech Co. Ltd, Beijing, China) was diluted 1:5 (product:water) and sprayed on the soil surface in the furrows receiving the PL treatment at a total rate of 450 L [ha.sup.-1] of product using a hand-pumped backpack sprayer.
Spring maize (Yuyu 22) was sown at a rate of 55 600 plants [ha.sup.-1] on 28 April 2007, 15 April 2008, 26 April 2009, and 24 April 2010 using a hole-sowing machine (Li et al. 2010). An additional 150 kg [ha.sup.-1] of N was applied as a topdressing in late June. Maize was harvested on 15 September 2007, 5 September 2008, 18 September 2009, and 17 September 2010. The ridge-and-furrow configuration was retained after the current crop was harvested. In 2008-10, mulches were reapplied 30 days before planting. Weeds were controlled manually as required during each crop growth season.
Sampling and measurement
A set of mercury-in-glass geothermometers with bent stems (Hongxing Thermal Instruments, Wuqiang County, Hebei Province, China) were placed in the middle of the furrow in every treatment plot at soil depths of 5, 10, 15, and 20cm. Soil temperature was recorded at 08:00, 14:00, and 20:00 hours from sowing to harvesting at 10-day intervals. Mean daily soil temperature was calculated as the mean of the three daily readings.
Soil water content was measured gravimetrically (w/w) to a depth of 2 m at 20-cm intervals using an 8-cm-diameter hand auger in the middle of the furrow at sowing time (0 days), jointing stage (60 days), tasseling stage (90 days), filling stage (120 days), and harvest time (140 days), in 2008-10. In each plot, three random soil samples were taken using a 54-mm-diameter steel core sampling tube, immediately before sowing in 2007. The soil cores were weighed wet, dried at 105[degrees]C for 48 h, and weighed again to determine bulk density (Chinese Academy of Sciences Nanjing Soil Research Institute 1983). Average bulk density to a depth of 2 m was 1.37 g [cm.sup.-3]. Gravimetric water content was multiplied by soil bulk density to obtain volumetric water content. Soil water storage (mm) was calculated for a 2-m profile by multiplying the mean soil volumetric water content by soil profile depth.
Rainfall was too low to drain down below 2 m and there was no irrigation, so evapotranspiration (ET) can be calculated using the following formula:
ET = P + [increment of W] (1)
where P is precipitation (mm) during the crop growing season, and [increment of W] is the difference in soil water storage at the beginning and the end of the experimental period.
Water-use efficiency was calculated using the following formula:
WUE = Y/ET (2)
where WUE is water-use efficiency (kg /ha.mm), Y is grain yield (kg /ha), and ET is the actual evapotranspiration (mm) during the growing season.
The SAS package was used to conduct analysis of variance tests (ANOVA). Least significant differences (1.s.d.) were used to detect mean differences between the treatments. Differences were considered statistically significant when P [less than or equal to] 0.05.
Results and discussion
Treatment effects over the 4 years were similar, so only the temporal variations in soil temperature during 2009 are reported (Fig. 3). Irrespective of depth, the effects on soil temperature of RHRHS and different mulching was larger during the early stages of growth because of sparse crop cover, while the effect decreased with canopy growth over time.
Soil temperature was consistently highest under PP, and lowest under PS, in each soil layer. At 5 cm depth, PP and PB produced significantly higher soil temperatures than CK from sowing to 70 days after sowing (DAS). Soil temperatures under PL and P were slightly higher than under CK from sowing to 60 DAS, but slightly lower than CK from 60 to 100 DAS. Soil temperature under PS was significantly lower than under CK up to 100 DAS. After 100 DAS, there were no differences in soil temperature among all treatments. Temporal variation in soil temperature at 10cm depth followed a similar trend to that at 5 cm, but the magnitude of temperature differences among the treatments decreased with the increase in soil depth. Soil temperatures below 10 cm depth were not affected by PL and P treatments. Compared with CK, soil temperature was increased under PP and PB by 0.4-2.3[degrees]C and 0.1-1.6[degrees]C, respectively, at 15 cm depth and by 0.2-1.5[degrees]C and 0.0-1.3[degrees]C, respectively, at 20 cm depth. In contrast, soil temperature was decreased under PS by 0.1-1.8[degrees]C and 0.1-1.1[degrees]C at depths of 15 and 20cm, respectively, compared with CK.
Mean soil temperature at 0-20cm was calculated by averaging the readings taken over the growing season, as shown in Table 1. Mean soil temperature with each of the treatments was ranked as follows: PP>PB>PL>P>CK> PS. Compared with CK, PP and PB significantly enhanced the soil temperature in the 0-20cm profile, while PS significantly reduced soil temperature. However, there were no significant differences in soil temperature between PL, P, and CK.
The results show that using different mulching materials in furrows had different effects on soil temperature. These results are consistent with those of Subrahmaniyan and Zhou (2008), who observed that soil temperature was higher under transparent film mulch, followed by degradable herbicidal film, and black polyethylene film mulches, whereas the soil temperature under straw mulch was lower than a non-mulched control at some growth stages of the crop. Film mulch prevents water exchange between the soil and air, which in turn reduces the latent heat flux and the exchange of heat between soil and air (Wang and Deng 1991). In our study, the PP treatment increased the soil temperature, generating the highest soil temperatures observed over the 4 years. At the sowing stage, the plant canopy was small enough to allow the majority of the plastic film area to receive solar energy and warm the topsoil. In the middle and later growth stages, full establishment of the plant canopy led to hardly any increase in the soil temperature with the plastic film compared with unmulched plots. These results are similar to those reported by Zhou et al. (2009). The temporal variations in soil temperature with PB were similar to PP, and the temperature values were always slightly lower under PB than PP, which was probably due to the lower transmittance of biodegradable film (Zhao et al. 2005).
Olasantan (1999) and Fabrizzi et al. (2005) observed that soil temperatures under straw mulching were higher during colder weather than during warmer weather when compared with nonmulched soil. Horton et al. (1996) reported that straw used to cover the soil surface has a higher albedo and lower thermal conductivity than bare soil, which consequently reduces the solar energy reaching the soil and reduces the magnitude of temperature increases during warm conditions. Our 4-year field experiment demonstrated that soil temperatures were reduced under PS. Moreover, the research of Fang et al. (2003) on the Loess Plateau showed that the soil temperature at 10 cm depth under a straw mulch was 1.4-4.0[degrees]C lower than non-mulched. This was in agreement with our study.
In the present study, the soil temperature under P was 0.1-1.0[degrees]C higher than under CK during the early stages, because of the plastic mulch on the ridges. This was consistent with reports by Li et al. (2001) and Ren et al. (2008). Immirzi et al. (2009) found that the temperatures recorded under liquid film were similar to those under soil covered with straw, while plastic film mulching induced slightly higher temperatures. This was probably because of the presence of an air gap beneath the plastic film, which produced a higher soil temperature than the sprayed liquid film mulch, which was in direct contact with the soil. Moreover, Schettini et al. (2007) reported that plastic film and biodegradable film produced higher temperatures than liquid film because they were more transparent to the solar radiation and less diffusive. Our results also showed that the soil temperature under PL was similar to the P treatment, but significantly lower than PP and PB, consistent with the results of the above studies.
Soil water content dynamics
Table 2 shows the soil water content dynamics in the 0-200 cm soil layers under all treatments during the five maize growing stages in 2008-10. (In 2007, the first year of the study, we only measured soil water content at sowing time and harvesting time.) The RPRHS treatments increased soil water content compared with CK in nearly all of the layers measured during the early growth stages (sowing and jointing stages), and this was more pronounced under PP, PB, and PS. Differences in precipitation during the winter fallow period (145 mm in 2008, 114mm in 2009, and 105 mm in 2010) meant that soil water content at the sowing stage was significantly higher under PP, PB, and PS than under CK at 0-120 cm depth in 2008, at 0-100 cm depth in 2009, and at 0-40 cm depth in 2010. The averaged profile soil water content (0-200 cm) over the 3 years was significantly increased with the PP, PB, and PS treatments compared with CK, by 20, 19, and 27 mm, respectively, at the sowing stage, and by 27, 29, and 34 mm, respectively, at the jointing stage.
In the middle growth stages (tasseling and filling stages), soil water content distribution was similar during 2008 and 2009. Soil water content was higher under PP and PB than under CK at 0-40 cm depth. However, soil water content at 80-180 cm depth was significantly lower with PP and PB than CK. Compared with CK, the average soil water content in 0-200 cm depth at the filling stage was 15 mm lower with PP and 14 mm lower with PB during 2008, and 14 and 11 mm lower during 2009, respectively. In 2010, the distribution of soil water content was different from 2008 and 2009, and no significant differences in soil water content were found between PP, PB, and CK in all the soil layers measured. This may have been related to the higher rainfall during this period in 2010 (i.e. 148 mm in 2008, 89 mm in 2009, and 233 mm in 2010). Soil water content was slightly higher under PS at the tasseling and filling stages during the three experimental years in nearly all of the soil layers measured, whereas there were no differences in soil water content between PL, P, and CK. In the later growth stage (maturity stage), the soil water content distribution for all treatments was similar among the experimental years. Soil water content was slightly higher with the RFRHS treatments than with CK at 0-100 cm depth, although slightly lower with PP and PB than with CK at depths from 100 to 200 cm.
Mulching in RFRHS with sand or gravel in the furrow can collect water from light rain and greatly inhibit soil water evaporation, which significantly improves soil water condition (Li et al. 2001; Wang et al. 2009). In the present study, the PP, PB, and PS treatments provided better rainwater harvesting and water conservation than CK and P, and the PS treatment performed best. Shen et al. (2011) indicated that soil water from sowing to joining stage was higher for degradable film covering than for open field, similar to the results of our study.
Maize yield and water-use efficiency
Maize yield varied between the four experimental seasons, with the highest yield recorded in 2008 and the lowest in 2007 (Table 3). Compared with CK, the RFRHS treatments significantly increased maize yields by 7-23% in 2007, 18-34% in 2008, 26-48% in 2009, and 25-47% in 2010. During the four seasons, no significant differences in maize yield were observed between PP and PB or between the PL and P treatments, although the yields of the first two treatments were always significantly higher than the latter two. In 2007, the maize yield with PS was significantly lower than with PP and PB, and significantly higher than with P and CK. However, yields with PS, PP, and PB were similar and were significantly higher than those with PL, P, and CK in 2008-2010. The 4-year average maize yields for each of the treatments were ranked as follows: PB > PP > PS > PL > P > CK. Compared with CK, the average maize yields with PP, PB, and PS were significantly increased by 2710 kg [ha.sup.-1] (35%), 2740 kg [ha.sup.-1] (35%), and 2620 kg [ha.sup.-1] (34%), respectively.
Evapotranspiration by maize increased with an increase in maize yield in all experimental years, except 2007. The ET values of PP, PB, and PS were significantly higher than those of PL, P, and CK in 2008-2010. Wang et al. (2010) reported that lodging decreased maize yields, and the later maize lodged, the lower was its yield. On 31 July 2007, heavy rain with strong winds at the experimental site caused maize lodging over a large area. At this time, the maize of RFRHS treatments was in the filling stage, and that of the CK treatment was still in the tasseling stage. The regeneration of maize in the RFRHS treatments was lower than that in CK after lodging, which was a main reason why water consumption of RFRHS treatments was lower than of CK. Variation in WUE followed a similar trend to grain yield. The RFRHS treatments had a significantly higher WUE than CK. Averaged over the four experimental years, the WUE with PP, PB, and PS was significantly increased by 30%, 31%, and 29%, respectively, compared with CK.
Straw mulching effects can depend on climatic conditions and soil type (Acharya et al. 2005). Application of straw mulch is restricted in some places because it is liable to lower the soil surface temperature and lead to a reduction in yield (Edwards et al. 2000; Gao and Li 2005). We found that soil temperature with PS was lower than with CK, but it had no negative impact on the increased yield and WUE. This was probably because soil water retention was better with PS, although the increased temperature effect with plastic film mulching on ridges can compensate for the effects of low temperature on maize growth, to some extent. Zhang and Yang (2008) reported that the application of liquid film mulch increased maize yield by 17.4% compared with the control. However, we found no difference in yield or WUE between PL and P treatments, which might be related to the composition of liquid film, or the film might have been more vulnerable to the environmental conditions that prevailed during film formation after spraying (Mahmoudpour and Stapleton 1997). In the present study, PP and PB had higher soil water content and temperature than CK during the early growth stages, which greatly enhanced the growth of maize in the early stages. At the jointing stage of maize, the 4-year average dry biomasses were 2790, 2760, 1490, 1590, and 1470 kg [ha.sup.-1] for the PP, PB, PS, PL, P, and CK treatments, respectively, and the dry biomass of the PP and PB treatments was significantly higher than that of CK and other treatments.
Rainfall during the maize growing season was 398 mm in 2007, 330mm in 2008, 378 mm in 2009, and 390 mm in 2010, while the average growing period rainfall over past 30 years was 380 mm. However, the maize yield followed the order: 2008 (drought year) >2010 (average year) >2009 (average year) >2007 (average year). Rainfall was lowest in 2008 during the maize growth stage, but maize yield and ET were highest. This was mainly due to the better soil water status before sowing. Table 2 shows that the soil water in 2008 was higher than in other years, and this provided a better soil water condition for maize emergence, growth, and yield. Previous studies indicate that the effect of RFRHS on yield increases could depend on the amount of precipitation during the crop growth season (Li et al. 2001; Tian et al. 2003). Ren et al. (2010) reported that, compared with a conventional fiat system, the increased yield provided by a rainwater harvesting system declined as rainfall increased during the corn growth period. In the present study, the trend of yield increase was 2009 >2010 >2008 >2007, which was inconsistent with the report of Ren et al. (2010). This might be related to the distribution of precipitation during the different maize growth stages in separate experimental years.
Mulching in RFRHS with sand or gravel in the furrow could increase crop yield and WUE (Li et al. 2001; Wang et al. 2009), but sand or gravel mulch is unfavourable for mechanisation of farming. Furrows mulched with plastic or biodegradable film increased soil temperature, which greatly enhanced maize growth during the early stage (Liu et al. 2011). Straw mulching reduced the soil temperature and plants grew slowly in the early stage of the growing season, which promoted maize growth in the middle and late stages (Chen et al. 2004). Our study found no obvious difference in increasing crop yield and WUE between the furrows being mulched with plastic film, biodegradable film, and maize straw. Degradable film or maize straw mulching in the furrows is simple in operation and easy to popularise compared with gravel and sand. Therefore, the methods could be considered effective measures for increasing crop yield and improving WUE.
There were obvious differences in the input costs of the various treatments, because of the use of mulching materials and labour (Table 4). Biodegradable film could be incorporated into soil by ploughing the field after crop harvesting, rather than using labour to remove it from the field. Thus, the PB treatment had reduced labour costs compared with PP. The PS treatment reduced the use of film and it had a lower input cost than PP and PB. The 4-year average input cost was ranked as follows: PP > PB > PS > PL > CK > P. The output value with the different treatments followed the order: PB > PP > PS > PL > P > CK, which was similar to the grain yield order. Net income was highest with PS followed by PB. Compared with CK, net income with PS and PB was increased by 2779 and 2752 CNY [ha.sup.-1], respectively. The output value of PL was slightly higher than that of P, whereas the net income was lower than with P. This was because the application of liquid film increased the input cost.
The use of plastic-covered ridges and furrows in a rainfall harvesting system, combined with mulches, can significantly improve soil water and temperature condition, promote crop growth, increase maize yield, and increase WUE, particularly the PP, PB, and PS treatments. In the long term, treatments with plastic-covered ridges and biodegradable-covered furrows (PB) and plastic-covered ridges and straw-covered furrows (PS) will not contaminate the environment and they will bring an increase in the income of farmers. Therefore, these two treatments are considered to be efficient for maize production in drought-prone, semi-humid regions of the Loess Plateau, China.
This work was supported by the China Support Program for Dryland Fanning in the 11th 5-year (2006BAD29B03) and 12th 5-year (2012BAD09B03) plan period. We are grateful to Mr Zhang Rui and Ren Shichun for managing the field experiment. We also would like to thank the staff of the Research Center of Dryland Fanning in Arid and Semiarid Areas, North-west A & F University. The English language used in this manuscript was improved by a professional English editor, Dr Duncan E. Jackson.
Received 29 September 2011, accepted 8 February 2012, published online 19 March 2012
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Rong Li (A,B), *, Xianqing Hou (A,B), *, Zhikuan Jia (A,B,C), Qingfang Han (A,B), and Baoping Yang (A,B)
(A) The Chinese Institute of Water-saving Agriculture, Northwest A&F University, Yangling 712100, Shaanxi, China.
(B) Key Laboratory of Crop Production and Ecology, Minister of Agriculture, Northwest A&F University, Yangling 712100, Shaanxi, China.
(C) Corresponding author. Email: email@example.com
* R. Li and X. Q. Hou contributed equally to this work.
Table 1. Averaged soil temperatures ([degrees]C) at 0-20 cm over the growing season under different treatments from 2007 to 2010 PP, Plastic-covered ridges and plastic-mulched furrows; PB, plastic-covered ridges and biodegradable-mulched furrows; PS, plastic-covered ridges and straw-mulched furrows; PL, plastic-covered ridges and liquid-mulched furrows; P, plastic-covered ridges and bare furrows; CK, conventional flat plot without mulching. Within columns, values followed by the same letter are not significantly different at P=0.05 Treatment 2007 2008 2009 2010 PP 23.4a 24.0a 24.2a 24.6a PB 23.1a 23.7a 23.8ab 24.4ab PS 20.7c 20.9c 21.9d 22.3d PL 22.Ob 22.7b 23.2bc 23.9bc P 22.2b 22.6b 23.3bc 23.7c CK 21.8b 22.4b 23.1c 23.5c l.s.d. (P=0.05) 0.9 0.8 0.6 0.6 Table 2. Soil water storage (mm) of 0-200 cm at different maize growth stages under different treatments in 2007-10 PP, Plastic-covered ridges and plastic-mulched furrows; PB, plastic-covered ridges and biodegradable-mulched furrows; PS, plastic-covered ridges and straw-mulched furrows; PL, plastic-covered ridges and liquid-mulched furrows; P, plastic-covered ridges and bare furrows; CK, conventional flat plot without mulching. Within columns, values followed by the same letter are not significantly different at P=0.05 Treatment Sowing Jointing Tasseling Milking Harvesting 2007 PP 445 -- -- -- 448a PB 445 -- -- -- 452a PS 445 -- -- -- 444a PL 445 -- -- -- 441ab P 445 -- -- -- 443a CK 445 -- -- -- 431b l.s.d. (P=0.05) -- -- -- -- 11 2008 PP 520a 488ab 465c 365c 414a PB 521a 488ab 465c 366c 412a PS 521a 495a 493a 390a 417a PL 504b 478bc 476b 378b 414a P 506b 474c 475b 377b 421a CK 499b 454d 462c 380ab 420a l.s.d. (P=0.05) 14 13 10 12 11 2009 PP 442ab 511ab 430c 340c 403b PB 441b 513a 431c 343c 401b PS 452a 515a 459a 372a 413a PL 439bc 507ab 442b 360b 412a P 433c 503b 439b 356b 406ab CK 426d 490c 430c 354b 410a l.s.d. (P=0.05) 11 13 10 10 8 2010 PP 447b 440b 411b 421b 418a PB 447b 444ab 411b 422b 416a PS 458a 451a 427a 438a 427a PL 443b 432b 409b 424b 422a P 443b 434b 409b 422b 418a CK 429c 416c 401b 425b 422a l.s.d. (P=0.05) 11 11 13 12 10 Table 3. Yield, evapotranspiration (ET), and water use efficiency (WUE) with different treatments in 2007-10 PP, Plastic-covered ridges and plastic-mulched furrows; PB, plastic-covered ridges and biodegradable-mulched furrows; PS, plastic-covered ridges and straw-mulched furrows; PL, plastic-covered ridges and liquid-mulched furrows; P, plastic-covered ridges and bare furrows; CK, conventional flat plot without mulching. Within columns, values followed by the same letter are not significantly different at P=0.05 Yield WUE (kg Yield (kg increase ET [ha.sup.-1] Treatment [ha.sup.-1]) (% of CK) (mm) [mm.sup.-1]) 2007 PP 9400a 23 395bc 24a PB 9300a 21 391c 24a PS 8530b 11 399bc 21b PL 8310bc 8 402b 21b P 8190c 7 400b 20c CK 7670d 0 412a 19d l.s.d. (P=0.05) 320 9 1 2008 PP 11 790a 33 437a 27a PB 11 850a 34 439a 27a PS 11 520a 30 434a 27a PL 10 560b 20 421b 25b P 10 400b 18 416b 25b C K 8840c 0 410b 22c l.s.d. (P=0.05) 388 13 1 2009 PP 10 100b 42 418a 24a PB 10 190ab 43 419a 24a PS 10 570a 48 418a 25a PL 9240c 29 406b 23b P 9020c 26 406b 22b CK 7140d 0 395c 18c l.s.d. (P=0.05) 440 12 1 2010 PP 10 710a 42 419a 26a PB 10 800a 44 421a 26a PS 11 040a 47 422a 26a PL 9500b 26 411b 23b P 9430b 25 416ab 23b CK 7520c 0 399c 19c l.s.d. (P=0.05) 363 8 1 Table 4. Average economic output and input costs of maize production between 2007-10 PP, Plastic-covered ridges and plastic-mulched furrows; PB, plastic-covered ridges and biodegradable-mulched furrows; PS, plastic-covered ridges and straw-mulched furrows; PL, plastic-covered ridges and liquid-mulched furrows; P, plastic covered ridges and bare furrows; CK, conventional flat plot without mulching. LC, Labour costs; MMC, mulching material cost; SFC, seed and fertiliser cost; IV, input value (CNY [ha.sup.-1]) =LC+MMC+SFC; OV, output value (CNY [ha.sup.-1]); NI, net income (CNY/ha)=0V--total IV; NID, net income difference (CNY/ha) from CK Treatment LCA MMC SFC IV OV NI NID PP 2700 1170 3500 7370 18 903 11 533 2353 PB 2250 1280 3500 7030 18 962 11 932 2752 PS 2250 1035 3500 6785 18 744 11 959 2779 PL 1800 885 3500 6185 16 928 10 743 1563 P 1575 585 3500 5660 16 667 11 007 1827 CK 1350 0 3500 4850 14 030 9 180 0 (A) Labour cost was 30 CNY per person per day; cost of plastic film was 13 CNY [kg.sup.-1], biodegradable film 14 CNY [kg.sup.-1], maize straw 0.1 CNY [kg.sup.-1], liquid film 7CNY [kg.sup.-1]; maize seed price was 1.80 CNY [kg.sup.-1]. The CNY is the Chinese currency unit.
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|Author:||Li, Rong; Hou, Xianqing; Jia, Zhikuan; Han, Qingfang; Yang, Baoping|
|Date:||Mar 1, 2012|
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