Qingfang Han

Effects of rainfall harvesting and mulching technologies on soil water, temperature, and maize yield in Loess Plateau region of China

Precipitation is the major factor limiting crop growth in the semi-arid Loess Plateau region of China. Ridge-and-furrow rainfall harvesting systems (RFRHS) with mulches are used to increase water availability to crops, thereby improving and stabilising agricultural production in the semi-arid region of China. We conducted a field experiment from 2007 to 2010 in the Weibei Highlands of China, to determine the influence of RFRHS with different mulching patterns on soil water content, temperature, water-use efficiency, and maize yield (Zea mays L.). Ridges were covered with standard plastic film in all RFRHS treatments, while different furrow treatments were mulched with standard plastic film (PP), biodegradable film (PB), maize straw (PS), or liquid film (PL), or left uncovered (P). A conventional flat treatment without mulching was used as the control. In the early stage of maize growth, the topsoil temperature (5–20 cm) under PP and PB was significantly (P < 0.05) higher than under the control, whereas the soil temperature under PS was significantly (P < 0.05) lower than under the control. Treatments PP, PB, and PS also significantly improved soil water content during early growth stages. There was no significant difference in soil water content between PS and the control during middle and late growth stages. However, the soil water content in the deep soil layers with PP and PB was less than that of the control. Soil temperature and soil water content of PL and P were slightly higher than the control during the whole growing season. Higher maize yield and water-use efficiency was found with PP, PB, and PS. Compared with the control, the 4-year average maize yield with PP, PB, and PS was significantly (P < 0.05) increased, by 35, 35, and 34%, while the average water-use efficiency increased by 30, 31, and 29%, respectively. Net income was highest with PS, followed by PB, where the 4-year average net income increased by 2779 and 2752 Chinese yuan (CNY) ha–1, respectively, compared with the control. Soil water and temperature conditions were improved, while the maize yield and net income were increased, when ridges were covered with standard plastic film and the furrows were mulched with either biodegradable film or straw. Therefore, these two treatments are considered most efficient for maize production in the drought-prone, semi-humid region of the Loess Plateau, China.

Effects of Wheat Straw Incorporation on the Availability of Soil Nutrients and Enzyme Activities in Semiarid Areas

Soil infertility is the main barrier to dryland agricultural production in China. To provide a basis for the establishment of a soil amelioration technical system for rainfed fields in the semiarid area of northwest China, we conducted a four—year (2007–2011) field experiment to determine the effects of wheat straw incorporation on the arid soil nutrient levels of cropland cultivated with winter wheat after different straw incorporation levels. Three wheat straw incorporation levels were tested (H: 9000 kg hm-2, M: 6000 kg hm-2, and L: 3000 kg hm-2) and no straw incorporation was used as the control (CK). The levels of soil nutrients, soil organic carbon (SOC), soil labile organic carbon (LOC), and enzyme activities were analyzed each year after the wheat harvest. After straw incorporation for four years, the results showed that variable straw amounts had different effects on the soil fertility indices, where treatment H had the greatest effect. Compared with CK, the average soil available N, available P, available K, SOC, and LOC levels were higher in the 0–40 cm soil layers after straw incorporation treatments, i.e., 9.1–30.5%, 9.8–69.5%, 10.3–27.3%, 0.7–23.4%, and 44.4–49.4% higher, respectively. On average, the urease, phosphatase, and invertase levels in the 0–40 cm soil layers were 24.4–31.3%, 9.9–36.4%, and 42.9–65.3% higher, respectively. Higher yields coupled with higher nutrient contents were achieved with H, M and L compared with CK, where these treatments increased the crop yields by 26.75%, 21.51%, and 7.15%, respectively.

Effects of straw incorporation on soil organic matter and soil water-stable aggregates content in semiarid regions of Northwest China.

The soil degradation caused by conventional tillage in rain-fed areas of northwest China is known to reduce the water–use efficiency and crop yield because of reduced soil porosity and the decreased availability of soil water and nutrients. Thus, we investigated the effects of straw incorporation on soil aggregates with different straw incorporation rates in semiarid areas of southern Ningxia for a three-year period (2008–2010). Four treatments were tested: (i) no straw incorporation (CK); (ii) incorporation of maize straw at a low rate of 4 500 kg ha−1 (L); (iii) incorporation of maize straw at a medium rate of 9000 kg ha−1 (M); (iv) incorporation of maize straw at a high rate of 13 500 kg ha−1 (H). The results in the final year of treatments (2010) showed that the mean soil organic carbon storage of the 0–60 cm soil layers were significantly (P<0.05) increased with H, M, and L, by 21.40%, 20.38% and 8.21% compared with CK, respectively. Straw incorporation increased >0.25 mm water-stable macroaggregates level, geometric mean diameter, mean weight diameter and the aggregate stability, which were ranked in order of increasing straw incorporation rates: H/M > L > CK. Straw incorporation significantly (P<0.05) reduced the fractal dimension in the 0–40 cm soil layers compared with CK. Our results suggest that straw incorporation is an effective practice for improving the soil aggregate structure and stability.

Plastic-Film Mulching for Enhanced Water-Use Efficiency and Economic Returns from Maize Fields in Semiarid China

Film mulch has gradually been popularized to increase water availability to crops for improving and stabilizing agricultural production in the semiarid areas of Northwest China. To find more sustainable and economic film mulch methods for alleviating drought stress in semiarid region, it is necessary to test optimum planting methods in same cultivation conditions. A field experiment was conducted during 2013 and 2014 to evaluate the effects of different plastic film mulch methods on soil water, soil temperature, water use efficiency (WUE), yield and revenue. The treatments included: (i) the control, conventional flat planting without plastic film mulch (CK); (ii) flat planting with maize rows (60 cm spacing) on plastic film mulch (70 cm wide); (iii) furrow planting of maize (60 cm spacing), separated by consecutive plastic film-mulched ridges (each 50 cm wide and 15 cm tall); (iv) furrow planting of maize (60 cm spacing), separated by alternating large and small plastic film-mulched ridges (large ridges: 70 cm wide and 15 cm tall, small ridges 50 cm wide and 10 cm tall); and (v) furrow-flat planting of maize (60 cm spacing) with a large plastic film-mulched ridge (60 cm wide and 15 cm tall) alternating with a flat without plastic film-mulched space (60 cm wide). Topsoil temperature (5–25 cm) was significantly (p < 0.05) higher in field plots with plastic film mulch than the control (CK), and resulted in greater soil water storage (0–200 cm) up to 40 days after planting. Maize grain yield and WUE were significantly (p < 0.05) higher with the furrow planting methods (consecutive film-mulched ridges and alternating film-mulched ridges) than the check in both years. Maize yield was, on average, 29% (p < 0.05) greater and 28% (p < 0.05) greater with these furrow planting methods, while the average WUE increased by 22.8% (p < 0.05) with consecutive film-mulched ridges and 21.1% (p < 0.05) with alternating film-mulched ridges. The 2-year average net income increased by 1559, 528, and 350 Chinese Yuan (CNY) ha−1 with the consecutive film-mulched ridges, furrow-flat planting and alternating film-mulched ridges, respectively, compared with the control (CK). We conclude that the consecutive film-mulched ridge method was the most productive and profitable for maize in this semi-arid area with limited and erratic precipitation.

Spatial Distribution of Soil Organic Matter and Nutrients in the Pear Orchard Under Clean and Sod Cultivation Models

Abstract The soil organic matter and nutrients are fundamental for the sustainability of pear production, but little is known about the spatial distribution of soil organic matter and nutrients in a pear orchard. With the soil of the pear (cv. Dangshansu on P. betulifolia Bunge. rootstock) orchard under clean and sod cultivation models as test materials, the experiment was conducted to evaluate spatial variability of soil organic matter (SOM), total nitrogen (STN), total phosphorus (STP), total potassium (STK), available nitrogen (SAN), and available potassium (SAK) in and between rows at different soil depths (0–60 cm). The SOM, STN, STP, STK, SAN and SAK of the different soil layers under the two tillage models were different in the vertical direction. The SOM, STN, STP and SAN in the 0–20 cm soil layer were higher than those in the 20–40 and 40–60 cm soil layers. The STK of 40–60 cm soil layer was higher than that in the 0–20 and 20–40 cm soil layers. The STK increased with the depth of soil in the vertical direction in the clean cultivated pear orchard. Variability of the SOM, STN, STP, STK, SAN and SAK of sample sites in between rows of the same soil layer was found in the pear orchard soil in the horizontal direction under clean and sod cultivation management systems, except that STK of all sites did not show the difference in identical soil layers in the pear orchard under clean cultivation. The sod cultivation model improved the SOM, STN, and STK in the 0–20 cm soil layer in the pear orchard, and the three components increased by 12.8, 12.7 and 7.3% compared to clean cultivation, respectively. The results can be applicable to plan collection of orchard soil samples, assess orchard soil quality, and improve orchard soil management practices.

Effects of rotational tillage practices on soil water characteristics and crop yields in semi-arid areas of north-west China

Winter wheat (Triticum aestivum L.) is a major crop grown generally in semi-arid areas of north-west China, and water deficiency is the major factor that limits crop yields. Between 2007 and 2010, we conducted a field experiment on winter wheat to investigate the effects of interval with no-tillage and subsoiling (rotational tillage) after crop harvesting on soil water characteristics and crop yields in semi-arid areas of southern Ningxia. Three tillage treatments were tested: no-tillage in year 1, subsoiling in year 2, and no-tillage in year 3 (NT/ST/NT); subsoiling in year 1, no-tillage in year 2, and subsoiling in year 3 (ST/NT/ST); and conventional tillage over years 1–3 (CT). The three-year comparative experiment showed that during the summer fallow, compared with CT, the NT/ST/NT and ST/NT/ST treatments improved mean soil water content at 0–2.0 m depth by 3.9% and 7.8%, respectively, and significantly (P < 0.05) increased mean rainfall storage efficiency by 15.4% and 26.7%. During the wheat growing season, mean soil water content with the NT/ST/NT and ST/NT/ST treatments was significantly higher (P < 0.05) than with the CT treatment (8.0% and 8.6% higher, respectively), and the two rotational tillage treatments significantly (P < 0.05) increased mean rainfall use efficiency compared with CT (by 9.3% and 10.7%, respectively). Yield improvements coupled with greater water-use efficiency occurred with the NT/ST/NT and ST/NT/ST treatments, i.e. mean grain yields were significantly (P < 0.05) increased by 9.6% and 10.7%, respectively, and water-use efficiency was significantly (P < 0.05) improved by 6.7% and 7.8% compared with the CT treatment. The results showed that the interval of no-tillage and subsoiling could improve soil status, and significantly increase crop yields and water-use efficiency. This method could have important applications in the semi-arid areas of north-west China.

Effect of Rotational Tillage on Soil Aggregates, Organic Carbon and Nitrogen in the Loess Plateau Area of China

Abstract In rain-fed semi-arid agroecosystems, continuous conventional tillage can cause serious problems in soil quality and crop production, whereas rotational tillage (no-tillage and subsoiling) could decrease soil bulk density, and increase soil aggregates and organic carbon in the 0–40 cm soil layer. A 3-year field study was conducted to determine the effect of tillage practices on soil organic carbon (SOC), total nitrogen (TN), water-stable aggregate size distribution and aggregate C and N sequestration from 0 to 40 cm soil in semi-arid areas of southern Ningxia. Three tillage treatments were tested: no-tillage in year 1, subsoiling in year 2, and no-tillage in year 3 (NT-ST-NT); subsoiling in year 1, no-tillage in year 2, and subsoiling in year 3 (ST-NT-ST); and conventional tillage over years 1–3 (CT). Mean values of soil bulk density in 0–40 cm under NT-ST-NT and ST-NT-ST were significantly decreased by 3.3% and 6.5%, respectively, compared with CT, while soil total porosity was greatly improved. Rotational tillage increased SOC, TN, and water-stable aggregates in the 0–40 cm soil, with the greatest effect under ST-NT-ST. In 0–20 and 20–40 cm soils, the tillage effect was confined to the 2–0.25 mm size fraction of soil aggregates, and rotational tillage treatments obtained significantly higher SOC and TN contents than conventional tillage. No significant differences were detected in SOC and TN contents in the > 2 mm and > 0.25 mm aggregates among all treatments. In conclusion, rotational tillage practices could significantly increase SOC and TN levels, due to a fundamental change in soil structure, and maintain agroecosystem sustainability in the Loess Plateau area of China.

Strategies for reducing the fertilizer application rate in the ridge and furrow rainfall harvesting system in semiarid regions

The ridge and furrow rainwater harvesting (RFRH) system is a promising water-saving planting technique for dryland farming, but we lack a full understanding of the effects of different fertilizer rates (N:P) on plant nutrient uptake and nutrient use efficiency (NuUE) in foxtail millet using this planting method, as well as the available nutrient residues in the soil. We conducted field studies (Loess Plateau, China) comparing RFRH planting (R) and traditional flat planting (T) at four different fertilizer rates to determine suitable fertilizer application rates for R during 2013–2015. Compared with T, R improved the soil moisture and the utilization of rainwater and fertilizer, thereby enhancing the grain yield, water use efficiency (WUE), grain nutrient uptake, and NUE in a dry year, but with no improvements in a rainy year. The grain yield and WUE exhibited parabolic increasing trends as the fertilizer application rate increased over three years, but no significant increase was found when the fertilizer rate exceeded 189:96 kg N:P ha−1 under R, which significantly reduced the NuUE and might waste nutrients. Therefore, we recommend R combined with 189:96 kg N:P ha−1 as a promising planting strategy for foxtail millet in semiarid areas.

Optimum Leaf Removal Increases Nitrogen Accumulation in Kernels of Maize Grown at High Density

Increasing plant density is one of the main approaches of achieving higher yields for modern maize crop. However, there exists leaf redundancy for high-density maize, and leaves of the upper canopy shade more competent leaves at the middle strata. In a two-year field experiments, Jinhai5, a semi-compact corn cultivar, was grown at a density of 105,000 plants ha−1 grown until 3 days after silking (3DAS), when plants were subjected to removal of the uppermost two leaves (S2), four leaves (S4) or six leaves (S6), with no leaf removal as control (S0). We evaluated the effects of leaf removal on N remobilization, photosynthetic capacity of the remaining leaves for N uptake, and N accumulation in kernels. Our present results concluded that, under high plant density, excising the uppermost two leaves promoted N remobilization from vegetative organs to kernels and enhanced photosynthetic capacity for N uptake, leading to an increased N accumulation in kernels (19.6% higher than control). However, four or six uppermost leaves removal reduced N remobilization from stem and photosynthesis for poor N uptake, resulting in 37.5 and 50.2% significantly reduced N accumulation in kernels, respectively.