Plastic-covered Ridge Research Articles

Grain-filling strategies of wheat of contrasting grain sizes under various planting patterns and irrigation levels

In a study comparing grain filling and yield in a large- and a small-grain-size wheat cultivar under two planting patterns and two irrigation regimes, plastic-covered ridge and furrow planting with sprinkler irrigation increased grain filling and yield in both cultivars. The largest contributors to grain yield were an extended active grain-filling period in Shuangda 1 and an increased mean grain-filling rate in XN538.

The effect of mulched ridge and furrow micro catchment water harvesting on red pepper yield and quality features in Bafra Plain of Northern Turkey

For two decades, promising results have been obtained by ridge-furrow rainwater harvesting systems (RWHS) to feed the increasing world population and cope with water scarcity and drought in semiarid and arid areas. A two-year study in Turkey's semi-humid Black Sea Region was conducted to examine RWHS's effects on harvested water, soil water content, red pepper growth, yield, quality attributes, water consumption, and crop water productivity (WPc), crop water stress index (CWSI). The profitability of the system was examined by economic analysis. For these purposes, three different polyethylene-covered ridge widths (RWHS1: 100 cm, RWHS2: 120 cm, and RWHS3: 140 cm) were considered. To allow the harvested water infiltration root zone and grow red pepper, 80 cm width furrow areas with double plant rows were left between the covered ridges on contours. To compare the RWHS treatments, three conventional rainfed farming or dry farming treatments (DFS1, DFS2, and DFS3) with 90 cm, 100 cm, and 110 cm plant row distances were considered. Each treatment was replicated three times in the randomized block design experiment. Besides, a multiple regression model was developed to estimate the runoff from the plastic-covered ridges by using independent parameters such as covered ridge ratios and rainfall amounts (R2 = 0.97). The red pepper consumed between 165 and 174 mm water in 2017 and 118–147 mm in 2018. Maximum red pepper yields, which increased by 68% in 2017 and 149% in 2018, were derived from RWHS1 as 33.2 and 27.19 t ha−1, respectively. As plastic-covered ridge width increased, red pepper yield decreased because of lowering plant density. RWHS improved red pepper yield and significantly increased leaf area, plant height, fruit length, and diameter. RWHS produced Turkey's highest red pepper WPc ratios, and RWHS1 improved WPc by 74% in 2017 and 169% in 2018. Although the red pepper consumed nearly the same amount of water under whole treatments, CWSI was lower under RWHS treatments. It was determined that sustainable red pepper farming according to the net income values under rainfed farmland in the region would not be possible without using rainwater harvesting systems such as RWHS1.

Multiannual soil mulching in agriculture: analysis of biogeochemical soil processes under plastic and straw mulches in a 3-year field study in strawberry cultivation

PurposeThe application of plastic mulching differs globally as well as climate, soils, crops, and agricultural practices, making it difficult to generalize the reported impacts on soil. Because literature is scarce about the influence of plastic mulching on soil under temperate, humid climate, the objective of this study was to understand how multiannual plastic mulching influences central soil parameters and processes under Central European cultivation conditions to evaluate its impact on soil quality in the long term.Materials and methodsCentral soil parameters and processes like leaching, aggregation, soil organic matter (SOM), and microbial biomass were investigated in a strawberry cultivation in Southwestern Germany. The field experiment compared a plastic-covered ridge–furrow system with subsurface drip irrigation (PC) to the same system with straw coverage (SC) in three soil layers (0–10, 10–30, and 30–60 cm) at seven dates within a 3-year period. Soil analyses comprised soil temperature and moisture, pH, bulk density, water-stable aggregates, soil organic carbon, dissolved organic carbon, and microbial biomass carbon and nitrogen.ResultsRainfall infiltration impeded by PC reduces soil moisture but neither reduces leaching nor promotes (macro-)aggregate formation or stability; however, it maintains a loose and friable soil structure in surface soil (0–5 cm), compared to SC. PC promotes SOM accumulation and shifted SOM composition to a more hardly degradable SOM, especially below the topsoil (10–60 cm). Furthermore, PC revealed no indications of an increased microbial biomass or activity accompanied with an enhanced SOM decomposition due to the shifted microclimate. The seasonal, time- and depth-dependent effects, observed in some parameters, emphasize the importance to include them in future studies for a more holistic process understanding.ConclusionOur study showed no indications that multiannual plastic mulching influences soil quality within the 3 years of this study. Further research is advisable to support our findings on a larger scale and longer time periods and across various soil and crop types.

Plastic-Covered Ridge-Furrow Planting Combined with Supplemental Irrigation Based on Measuring Soil Moisture Promotes Wheat Grain Yield and Irrigation Water Use Efficiency in Irrigated Fields on the Loess Plateau, China

The purpose of this study was to investigate whether combining plastic-covered ridge and furrow planting (RF) and supplemental irrigation based on measuring soil moisture (SIMSM) can increase the grain yield and water use efficiency (WUE) of wheat (Triticum aestivum L.) in irrigated fields of Loess Plateau, China. In 2016–2018, the experiment was conducted at Doukou experimental farm (34°36′ N, 108°52′ E) with two plant systems (RF and traditional planting (TF)) and three irrigation treatments (S1 and S2: SIMSM with a target relative soil water content of 85% and 100%, respectively). The results suggest that under the TF system, SIMSM decreased the grain yield and nitrogen utilization. The reason for this may be the local low precipitation. However, the combination of RF and S2 significantly increased the WUE, protein and wet gluten concentration in the grain. In addition, the grain yield of the RF plus S2 treatment was not significantly different than that of the traditional irrigation method. These results suggest that combining RF and SIMSM with a target relative soil water content of 100% is beneficial to the synergistic improvement of the wheat yield, the wheat quality, and the water and fertilizer use efficiency in irrigated fields on the Loess Plateau.

Ridge-furrow planting promotes wheat grain yield and water productivity in the irrigated sub-humid region of China

Determining methods for increasing irrigation water productivity is important for sustaining high wheat grain yields in the irrigated region of the Loess Plateau in China. Plastic-covered ridge and furrow planting has been widely applied in dryland farming, as it markedly increases precipitation productivity and crop yields. However, whether this planting system can significantly increase irrigation water productivity and whether it can reduce the irrigation volume for high-yielding wheat production in irrigated regions of the Loess Plateau are unclear. In the present study, plastic-covered ridge and furrow planting and traditional flatbed planting were performed at four irrigation levels. The objective was to investigate whether applying plastic-covered ridge and furrow planting to an irrigated farmland system could reduce the irrigation water requirements and increase water productivity for high-yielding wheat production. The results suggested that plastic-covered ridge and furrow planting significantly increased soil moisture content and increased both grain yield and water productivity of wheat. At the 0, 400, 1200, and 2000 m3 ha−1 irrigation levels, compared with that resulting from traditional flatbed planting, the grain yield resulting from plastic-covered ridge and furrow planting was 51.7 %, 64.8 %, 25.5 %, and 5.84 % greater, respectively. At the high-grain-yield level (6–7 t ha−1), the plastic-covered ridge and furrow planting system at 1200 m3 ha−1 irrigation conserved 40 % of irrigation water during wheat production. And it coordinated the relationships among grain yield, quality, water protuctivity and for wheat production. These findings show that the plastic-covered ridge and furrow planting system with 1200 m3 ha-1 irrigation is suitable for sustainable high-yielding wheat production in the irrigated regions of the Loess Plateau of China.

Supplemental irrigation strategy for improving grain filling, economic return, and production in winter wheat under the ridge and furrow rainwater harvesting system

The plastic-covered ridge and furrow rainwater harvesting (RFRH) system has been used widely to enhance crop productivity in the semiarid regions of China. We conducted a field study during 2015–2017 where the RFRH method was combined with deficit irrigation to decrease the irrigation water usage and improve the crop water productivity (CWP) and irrigation water productivity (IWP). Under the RFRH system, the amount of irrigation was reduced by half compared with that under traditional flat planting (TF) with border irrigation due to the effects of precipitation harvesting. Half of the deficit irrigation was supplied before wintering and the remaining half at the jointing stage. The following eight treatments were tested: RFRH system with 75 mm deficit irrigation (R75), 37 mm irrigation (R37), 18 mm irrigation (R18), and 0 mm irrigation (R0); TF cultivation with 150 mm irrigation (F150), 75 mm irrigation (F75), 37 mm irrigation (F37), and 0 mm irrigation (F0). The results showed that the irrigation volume doubled under conventional border irrigation but the soil water storage was greater under RFRH with deficit irrigation. The R75 treatment resulted in significantly greater soil water storage, reduced evapotranspiration (44.2%), and a higher grain yield (14.6%), thereby increasing CWP (64.8%), ICWP (irrigation crop water productivity) (44.2%), and IWP (57.0%) compared with F150. R75 improved the biomass per plant, leaf area index, and net income for farmers (by 17.5%) compared with F150. Thus, we recommend R75 for decreasing the irrigation water usage and increasing the effective consumption of precipitation in semiarid regions.

Mulching mode and planting density affect canopy interception loss of rainfall and water use efficiency of dryland maize on the Loess Plateau of China

High and efficient use of limited rainwater resources is of crucial importance for the crop production in arid and semi-arid areas. To investigate the effects of different soil and crop management practices (i.e., mulching mode treatments: flat cultivation with non-mulching, flat cultivation with straw mulching, plastic-covered ridge with bare furrow and plastic-covered ridge with straw-covered furrow; and planting density treatments: low planting density of 45,000 plants/hm2, medium planting density of 67,500 plants/hm2 and high planting density of 90,000 plants/hm2) on rainfall partitioning by dryland maize canopy, especially the resulted net rainfall input beneath the maize canopy, we measured the gross rainfall, throughfall and stemflow at different growth stages of dryland maize in 2015 and 2016 on the Loess Plateau of China. The canopy interception loss was estimated by the water balance method. Soil water storage, leaf area index, grain yield (as well as it components) and water use efficiency of dryland maize were measured or calculated. Results showed that the cumulative throughfall, cumulative stemflow and cumulative canopy interception loss during the whole growing season accounted for 42.3%–77.5%, 15.1%–36.3% and 7.4%–21.4% of the total gross rainfall under different treatments, respectively. Soil mulching could promote the growth and development of dryland maize and enhance the capability of stemflow production and canopy interception loss, thereby increasing the relative stemflow and relative canopy interception loss and reducing the relative throughfall. The relative stemflow and relative canopy interception loss generally increased with increasing planting density, while the relative throughfall decreased with increasing planting density. During the two experimental years, mulching mode had no significant influence on net rainfall due to the compensation between throughfall and stemflow, whereas planting density significantly affected net rainfall. The highest grain yield and water use efficiency of dryland maize were obtained under the combination of medium planting density of 67,500 plants/hm2 and mulching mode of plastic-covered ridge with straw-covered furrow. Soil mulching can reduce soil evaporation and retain more soil water for dryland maize without reducing the net rainfall input beneath the maize canopy, which may alleviate the contradiction between high soil water consumption and insufficient rainfall input of the soil. In conclusion, the application of medium planting density (67,500 plants/hm2) under plastic-covered ridge with bare furrow is recommended for increasing dryland maize production on the Loess Plateau of China.

Effects of rainwater harvesting planting combined with deficiency irrigation on soil water use efficiency and winter wheat (Triticum aestivum L.) yield in a semiarid area

The plastic-covered ridge and furrow rainwater harvesting planting system (RFRHP) has been widely used for increasing and stabilizing the crop productivity in the semiarid areas of northwest China. During 2012–2015, we performed a consecutive field experiment to evaluated the influence of rainwater harvesting planting with supplementary irrigation (RI) on the water irrigation use and water use efficiency by winter wheat in a semiarid climate using the following 8 treatments: the rainwater harvesting planting system supplemented with 375 m3 ha−1 irrigation during the early growth stage (R1), both the early and late stages (R2), late growth stage (R3), and no irrigation during whole winter wheat growth stage (R0); the traditional flat planting supplemented with 750 m3 ha−1 irrigation during the early growth stage (B1), both the early and late stages (B2), late growth stage (B3), and no irrigation during whole winter wheat growth stage (B0). We found that although the irrigation amount was double under traditional flat planting, but the soil water content in the 0–120 cm soil layer did not differ significantly between the rainwater harvesting planting with supplementary irrigation treatments (RI) and border irrigation treatments (BI). The rainwater harvesting irrigation (R1, R2, and R3) treatments reduced the irrigation water amounts required (750–1125 m3 ha−1) and alleviated drought stress during key winter wheat growth periods, it also could maintain higher grain yield (1.9%) without irrigation or with irrigation amount reduction by 50%. The irrigation water utilization efficiency of rainwater harvesting irrigation (RI) treatments under the condition of irrigation amounts reduction by 50% was improved significantly, i.e. compared with border irrigation (BI) treatments, the irrigation water use efficiency (IWUE) and water productivity (IWP) increased by 0.9–1.1 and 0.2-0.6 times, respectively, and the net incomes of farmers could increase by 718 Chinese Yuan ha−1.

Impacts of different mulching patterns in rainfall-harvesting planting on soil water and spring corn growth development in semihumid regions of China

Rain-harvesting planting can improve crop biomass and enhance precipitation use efficiency in rainfed semiarid areas. In this study, field trials were conducted during summer 2007–2010 to determine the impacts of different mulching patterns in rainfall harvesting planting on spring corn growth and development in a typical semihumid dryland farming area of the Loess Plateau in China, which is characterised by spring droughts. Rain-harvesting ridges and planting furrows were mulched with 8% biodegradable film (RCSB), liquid film (RCSL), or not mulched (RCSN), and bare land drilling without mulching served as the control (CF). We found that the rain-harvesting effects of ridges and the evaporation-inhibiting and moisture-conserving effects of mulching materials during the spring corn growing season significantly increased water storage in the 0–100cm soil layer (P<0.05) compared with CF, where mulching was more beneficial than the non-mulching treatments. In the 100–200cm soil layers, there were no significant effects (P>0.05) of the treatments on water storage. During 2007–2010, the average plant height increased by 26.6%, 15.4%, and 11.1% under RCSB, RCSL, and RCSN relative to CF respectively, whereas the per plant biomass increased by 26.6%, 15.4%, and 11.1% under these treatments, and the grain yield increased by 32.3%, 17.5%, and 15.0%. Therefore, in the semihumid dryland farming areas of the Loess Plateau, rain-harvesting planting greatly increased the growth, development, and dry matter accumulation by spring corn, thereby enhancing its biomass yield, whereas the plastic-covered ridges and furrows mulched with biodegradable films substantially increased the yield-enhancing effects.

Effect of rainfall concentration with different ridge widths on winter wheat production under semiarid climate

Abstract Ridge and furrow rainfall concentration (RC) system has gradually been popularized to increase water availability to crops for improving and stabilizing agricultural production in the semiarid area of northwest China. The system is comprised of two elements: the plastic-covered ridge serves as rainfall harvesting zones and the furrow serves as planting zones. To make this system more perfect for alleviating drought stress in semiarid region, it is necessary to test optimum planting systems. A field experiment was conducted from 2007 to 2010 to evaluate the effects of RC planting on soil moisture, wheat yield and water use efficiency ( WUE ) under different ridge widths. Four planting systems were designed (RC 40 : 40 cm ridge with 60 cm furrow width, RC 60 : 60 cm ridge with 60 cm furrow width, RC 80 : 80 cm ridge with 60 cm furrow width, and CF: conventional flat without ridging). The results showed that RC planting can significantly increase soil moisture in 0–200 cm during the growing seasons of winter wheat. The rainfall-harvesting effect increased with ridge width increasing. Winter wheat yield and WUE was significantly higher under RC 60 than under CF by 405.1 kg ha − 1 and 2.39 kg mm − 1 ha − 1 , respectively, on average across the three experimental years ( P 60 can benefit winter wheat cropping for higher yield through improving soil moisture. It could be concluded that the RC planting system with 60 cm ridge and furrow width will offer a sound opportunity for sustainable farming in semiarid dryland agricultural area.

Effect of Different Mulches under Rainfall Concentration System on Corn Production in the Semi-arid Areas of the Loess Plateau.

The ridge and furrow farming system for rainfall concentration (RC) has gradually been popularized to improve the water availability for crops and to increase the water use efficiency (WUE), thereby stabilizing high yields. In the RC system, plastic-covered ridges are rainfall harvesting zones and furrows are planting zones. In this study, we optimized the mulching patterns for RC planting to mitigate the risks of drought during crop production in semi-arid agricultural areas. We conducted a four-year field study to determine the effects on corn production of mulching with 0.08-mm plastic film, maize straw, 8% biodegradable film, liquid film, bare furrow, and conventional flat (CF) farming. We found that RC significantly increased (P > 0.05) the soil moisture storage in the top 0–100 cm layer and the topsoil temperature (0–10 cm) during the corn-growing season. Combining RC with mulching further improved the rain-harvesting, moisture-retaining, and yield-increasing effects in furrows. Compared with CF, the four-year average yield increased by 1497.1 kg ha–1 to 2937.3 kg ha–1 using RC with mulch treatments and the WUE increased by 2.3 kg ha–1 mm–1 to 5.1 kg ha–1 mm–1.

The Effect of Plastic-Covered Ridge and Furrow Planting on the Grain Filling and Hormonal Changes of Winter Wheat

Although plastic-covered ridge and furrow planting (RF) has been reported to produce substantial increases in the grain weight of winter wheat, the underlying mechanism is not yet understood. The present study used two cultivars, Xinong 538 and Zhoumai 18, and RF and traditional flatten planting (TF, control) with the objective of investigating the effect of RF on wheat grain filling and the possible relationship of hormonal changes in the wheat grains under RF to grain filling. The results indicated that RF significantly increased the grain weight, although the effects on grain filling were different: RF significantly increased the grain-filling rate and grain weight of inferior grains, whereas RF had no significant effect on grain-filling rate and grain weight of superior grains. The final grain weight of inferior grains under RF was 39.1 and 50.7 mg for Xinong 538 and Zhoumai 18, respectively, 3.6 and 3.4 mg higher than the values under TF. However, the final grain weight of superior grains under RF was only 0.6 and 0.8 mg higher than under TF for Xinong 538 and Zhoumai 18, respectively. RF significantly decreased the ethylene and gibberellic acid content in the inferior grains and increased the indole-3-acetic acid, abscisic acid and zeatin + zeatin riboside content in the inferior grains; however, no significant difference between RF and TF was observed for the hormonal content in the superior grains. Based on these results, we concluded that RF significantly modulated hormonal changes in the inferior grains and, thus, affected the grain filling and grain weight of the inferior grains; in contrast, RF had no significant effect on grain filling, grain weight and hormonal changes in the superior wheat grains.

Effect of Different Mulches on Harvested Rainfall Use Efficiency for Corn (Zea mays L.) in Semi-Arid Regions of Northwest China

A three-year field experiment was conducted to determine how integrating different furrow-applied mulches would influence the yield and water use efficiency (WUE) for corn (Zea mays L.) cultivated under a plastic-covered ridge and furrow rainwater harvesting (PRFRH) system in semi-arid lands of China's Loess Plateau. The effect of the mulching treatments in combination with PRFRH was compared to the conventional flat (control, T1). The furrow-applied mulching treatments and their designation were: none or bare furrow (T2); liquid film (T3); 8% biodegradable film (T4); 10-cm thick layer of corn stover (T5); and 0.08 mm thick plastic film (T6). Corn was planted in the furrows on either side of the plastic-covered ridges of the plots for treatments T2 though T6. Soil moisture was measured gravimetrically on auger samples taken at 6 locations in each plot at intervals of 20 cm from the 0 to 200 cm depth. In all years, soil moisture storage at the 0–100 cm depth was significantly higher (p < 0.05) in the T2 to T6 treatment plots compared to T1. No such effect was observed for the 100–200 cm depths. The integrated use of PRFRH and furrow-applied mulching performed better than the bare furrow treatment increasing the three-year average grain yield and harvest index (HI). WUE decreases followed the order: T6 > T4 > T3 > T2 > T5 > T1, indicating that mulching most likely reduced soil evaporation losses and suggesting that integrated PRFRH + mulch systems has potential to increase crop sustainability in this semiarid region.

Effects of Water-Collecting and -Retaining Techniques on Photosynthetic Rates, Yield, and Water Use Efficiency of Millet Grown in a Semiarid Region

Field experiments were conducted in 2003 and 2004 to study the effects of plastic ridges and furrow film mulching (plastic film on sowing, as well as plastic film on flat soil and hole sowing) and chemicals (a drought resistant agent and a water-retaining agent) on growth, photosynthetic rate, yield, and water use efficiency (WUE) of spring millet (Setaria italica L.). The experimental results showed that water-collecting and -retaining techniques can effectively increase soil moisture content, the leaf photosynthetic rate and crop growth. Due to increased soil moisture under the plastic-covered ridge and furrow water-collecting in July and August, dry matter and plant height had a increase at the booting stage (late growth advantage). However, the plastic-covered flat soil and hole sowing reduced soil evaporation during early growth, the increase of dry matter and plant height appeared at the seedling stage (early growth advantage). Plastic-covered ridge and furrow sowing supplemented with chemical reagents had significant positive effects on water collection and soil moisture retention. Improvement of soil moisture resulted into the increase of the photosynthetic rate, dry matter accumulation yield and WUE. The water-collecting and -retaining techniques can improve WUE and enhance crop yield. Correlation analysis demonstrated that the photosynthetic rate under the water-collecting and -retaining techniques was significantly associated with the soil moisture, but had no significant relationship with leaf chlorophyll content. Plastic-covered ridge and furrow sowing supplemented with chemical reagents increased the yield and WUE by 114% and 8.16 kg ha−1 mm−1, respectively, compared with the control; while without the chemical reagents the yield and WUE were 95% and 7.42 kg ha−1 mm−1 higher, respectively, than those of the control.

Ridge and Furrow Method of Rainfall Concentration For Fertilizer Use Efficiency in Farmland Under Semiarid Conditions

A plastic-covered ridge and furrow farming of rainfall concentration (RC) system was comprised of two elements: the plastic-covered ridges served as a rainfall harvesting zone and the furrows as a planting zone. The purpose of this study was to examine the effect of RC on farmland fertilizer utilization under three rainfall levels (230, 340, and 440 mm) during the corn growing seasons of 2006 and 2007. The results indicated that with the rainfalls ranging within 230-440 mm, the RC system can increase grain yields and nutrient use efficiency (NUE, including NUEN, NUEP, and NUEK) of corn. In 2006, when compared to conventional flat (CF) practice, the grain yield, water use efficiency (WUE), NUEN, NUEP, and NUEK in the RC system increased by 75.4%, 73.3%, 36.1%, 43.0%, and 49.1%, respectively, at 230-mm rainfall, and by 36.7%, 40.2%, 25.0%, 18.2%, and 12.0%, respectively, at 340-mm rainfall, but there was no significant difference between the RC440 and CF440 patterns. In 2007, the grain yield, WUE, NUEN, NUEP, and NUEK were 82.8%, 77.4%, 39.4%, 36.9% and 38.2%, respectively, higher in the RC230 plots than in the CF230 plots, 43.4%, 43.1%, 17.2%, 16.1%, and 14.0%, respectively, higher in the RC340 plots than in the CF340 plots, and the grain yield, WUE and NUEN were 11.2%, 9.5%, and 14.0%, respectively, higher in the RC440 plots than in the CF440 plots, but there was no significant difference for NUEP and NUEK between RC440 and CF440. In conclusion, we suggest that the optimal rainfall upper limit for RC system should be below 440-mm rainfall amounts to improve the fertilizer use efficiency in farmland of corn plants in this experiment.

Effects of rainfall harvesting and mulching technologies on water use efficiency and crop yield in the semi-arid Loess Plateau, China

In semi-arid areas, crop growth is greatly limited by water. Amount of available water in soil can be increased by surface mulching and other soil management practices. Field experiments were conducted in 2005 and 2006 at Gaolan, Gansu, China, to determine the influence of ridge and furrow rainfall harvesting system (RFRHS), surface mulching and supplementary irrigation (SI) in various combinations on rainwater harvesting, amount of moisture in soil, water use efficiency (WUE), biomass yield of sweet sorghum ( Sorghum bicolour L.) and seed yield of maize ( Zea mays L.). In conventional fields without RFRHS, gravel-sand mulching produced higher biomass yield than plastic-mulching or straw-mulching. In plastic-mulched fields, an increasing amount of supplemental irrigation was needed to improve crop yield. There was no effect of RFRHS without plastic-covered ridge on rainwater harvesting when natural precipitation was less than 5 mm per event. This was due to little runoff of rainwater from frequent low precipitation showers, and most of the harvested rainwater gathered at the soil surface is lost to evaporation. In the RFRHS, crop yield and WUE were higher with plastic-covered ridges than bare ridges, and also higher with gravel-sand-mulched furrows than bare furrows in most cases, or straw-mulched furrows in some cases. This was most likely due to decreased evaporation with plastic or gravel-sand mulch. In the RFRHS with plastic-covered ridges and gravel-sand-mulched furrows, application of 30 mm supplemental irrigation produced the highest yield and WUE for sweet sorghum and maize in most cases. In conclusion, the findings suggested the integrated use of RFRHS, mulching and supplementary irrigation to improve rainwater availability for high sustainable crop yield. However, the high additional costs of supplemental irrigation and construction of RFRHS for rainwater harvesting need to be considered before using these practices on a commercial scale.

Rainfall concentration for increasing corn production under semiarid climate

The ridge and furrow farming of rainfall concentration (RC) system is being promoted to increase water availability to crops for improving and stabilizing agricultural production in the semiarid Loess region of northwest China. In the system, plastic-covered ridges serve as rainfall harvesting zones and furrows serve as planting zones. In recent years, however, the current RC practices are still confined to rural family units for very limited supplemental irrigation purposes. To adopt this system for large-scale use in the semiarid region and bring it into full play, it is necessary to test the befitting rainfall range for RC farming. A field study (using corn as an indicator crop) combined with rainfall simulation was designed to determine the effects of RC practices on soil water content, crop yield and water use efficiency (WUE) under three rainfall levels (230 mm, 340 mm and 440 mm) during the growing seasons of 2006 and 2007. The results indicated that with the rainfalls ranging within 230–440 mm, RC system can increase soil water content in 0–100 cm and temperature conditions in the topsoil (0–10 cm) in furrows by 5–12% and 0.7–1 °C, respectively. The corn seedlings emerged 1–2 days earlier, the developmental stages generally occurred earlier, and the plant height and total dry matter all significantly increased ( P < 0.05). In 2006, compared to conventional flat (CF) practice, the grain yield and WUE in the RC system increased by 75.4% and 73.3%, respectively at 230 mm rainfall, and by 36.7% and 40.2%, respectively at 340 mm rainfall, but there was no significant difference between the RC 440 and CF 440 patterns. In 2007, the grain yield and WUE were 82.8% and 77.4%, respectively higher in the RC 230 plots than in the CF 230 plots, 43.4% and 43.1%, respectively higher in the RC 340 plots than in the CF 340 plots, and 11.2% and 9.5%, respectively higher in the RC 440 plots than in the CF 440 plots. Combining yield and WUE, it could be concluded that the optimal rainfall upper limit for RC system is below 440 mm rainfall in the experiment. In the case of corn, the adoption of RC practice in the 230–440-mm rainfall area will make the system more attractive during the whole growth period and offer a sound opportunity for sustainable farming under semiarid climate.

Rainfall harvesting on slopes using contour furrows with plastic-covered transverse ridges for growing Caragana korshinskii in the semiarid region of China

A rainwater harvesting system on slopes using contour furrows with plastic-covered transverse ridges designed to be used in small rainfall dominated areas of the semiarid loess region of China has been tested from 2001 to 2004. The system consisted of constructing contour furrows on the loess slope at a distance of 5 m with plastic-covered transverse ridges built in the furrows between shrubs of Caragana korshinskii. There were three treatments in the study: (1) plastic-covered ridge with gravel-mulched furrows (T1), (2) plastic-covered ridge with bare furrows (T2), and (3) control (no ridge and no contour furrow) (T3). The experimental results indicated that runoff from the natural loess slope was small and variable, and only produced from a few rainfall events with high intensity. Runoff efficiency averaged 13.8, 4.5, 1.4, and 0.4% in 2001, 2002, 2003, and 2004, respectively. However, the plastic-covered ridges accumulated runoff from most rainfall events, particularly from the light rains less than 5 mm. So the natural loess slope between the furrows and the plastic-covered ridges in the furrows can complement each other, i.e., the plastic-covered ridges induce runoff from small rainfall to the planted area, and the natural loess slope between the furrows concentrate runoff from heavy rainfall, thus improving rain use efficiency. The total runoff collected from both the natural loess slope and the plastic-covered ridges to the planted area in the furrows was 231, 143, 88, and 59 mm in 2001, 2002, 2003, and 2004, respectively. Soil moisture storage in the 200-cm deep soil layer was obviously higher for T1 and T2 than for T3, and C. korshinskii showed a significant improvement in growth for the T1 and T2 treatments. Therefore the combination of contour furrows and plastic-covered ridges as rainwater harvesting system may have a great potential development in the small rainfall dominated arid regions of China.

Influence of various in situ rainwater harvesting methods on soil moisture and growth of Tamarix ramosissima in the semiarid loess region of China

The influence of different in situ rainwater harvesting and moisture conservation methods on soil moisture storage and growth of Tamarix ramosissima was studied in the semiarid loess region of China from 2002 to 2004. The treatments included control (T1), trench (T2), saucer covered by plastic film (T3), bare ridge and bare furrow (T4), plastic-covered ridge and bare furrow (T5), and plastic-covered ridge and gravel-covered furrow (T6). The results indicated that soil water storage for the T5 and T6 was significantly higher than the control. The T6 treatments produced the highest amount of soil water storage, 18–137 mm more than the controls at soil depth of 0–100 cm and 40–75 mm at soil depth of 100–200 cm. No significant differences in soil water storage were found between the T2, T3, T4 and the control treatments at soil depth of 0–100 cm, but soil water storage at soil depth of 100–200 cm was significantly higher for the T2, T3, T4 treatment than the control. Rainwater harvesting and moisture conservation treatments increased growth of T. ramosissima, tree height was significantly higher for the rainwater harvesting and moisture conservation treatments than the controls. Tree height, crown diameter and collar girth for the T6 treatments increased by 70, 57 and 79% as compared to the controls. No significant differences in crown diameter and collar girth were observed between T1, T2 and T3 or T4 and T5 treatments in some years. The effectiveness of the different treatments for the tree height, crown diameter and collar girth was in the order of T6, T5, T4, T3, T2 and T1.

Increasing potato yields with additional water and increased soil temperature

Many water saving practices have been adopted to dryland crop production such as in semiarid loess regions of China. In the present study, a field experiment was conducted to examine the yield promotion of potato crops cultivated with in plastic-covered ridges and supplied with water from a furrow rainfall harvesting (PRFRH) system. The experiment included seven treatments: (1) 30 cm wide ridge covered with plastic film (P30), (2) 45 cm wide ridge covered with plastic film (P45), (3) 60 cm wide ridge covered with plastic film (P60), (4) 30 cm wide ridge without covering (B30), (5) 45 cm wide ridge without covering (B45), (6) 60 cm wide ridge without covering (B60), (7) soil surface flat without covering (B0). The PRFRH system increased temperature and availability of nutrients in the ridges, and maintained soil moisture in ridges. It promoted crop growth during the early period and diminished water stress at the later stages of potato growth. Potato yield as well as the water use efficiency in the PRFRT system was significantly ( P < 0.01) higher than in the other systems. The best ridge width was between 40 and 45 cm.