Huanwen Gao

Effects of 15 years of conservation tillage on soil structure and productivity of wheat cultivation in northern China

An understanding of long-term tillage and straw management impact on soil structure and productivity is necessary for the further development of conservation tillage practice in dryland farming areas. Data from a 15-year field experiment conducted in Shanxi, on the loess plateau of northern China, were used to compare the long-term effects of no-till and residue cover (NTSC) with conventional tillage (CT) in a winter wheat (Triticum aestivum L.) monoculture. Long-term CT and straw removal resulted in poor soil structure and low productivity. Mean soil bulk density in NTSC was 1.5% less than in CT and capillary porosity ( 2 mm was much greater for NTSC in the 0–0.20 m profile. Soil organic matter and total N and P were 27.9%, 25.6%, and 4.4% greater in NTSC, respectively, and earthworms (19/m2) were found only in the no tillage treatment. Crop yield and water use efficiency tended to be higher under NTSC than under CT, especially in the years of low rainfall, suggesting that the change in soil structure has provided a better environment for crop development. Our 15-year experimental data indicate that NTSC is a more sustainable farming system, which can improve soil structure, and increase productivity with positive environmental impacts in the rainfed dryland farming areas of northern China.

Traffic and tillage effects on wheat production on the Loess Plateau of China: 1. Crop yield and SOM

Challenges for dryland farming on the Loess Plateau of China are continuous nutrient loss, low soil organic matter and crop yield, and soil degradation. Controlled traffic, combined with zero or minimum tillage and residue cover, has been proposed to improve soil structure and crop yield. From 1998 to 2006, we conducted a field experiment comparing soil organic matter and wheat productivity between controlled traffic and conventional tillage farming systems. The field experiment was conducted using 2 controlled traffic treatments (zero tillage with residue cover and no compaction, shallow tillage with residue cover and no compaction) and a conventional tillage treatment. Results showed that controlled traffic treatments significantly increased soil organic matter and microbial biomass in the 0–0.30 m soil profile. Controlled traffic with zero tillage significantly increased total N in the 0–0.05 m soil profile. The mean yield over 8 years of controlled traffic treatments was >10% greater than that of conventional tillage. Controlled traffic farming appears to be a solution to the cropping problems faced on the Loess Plateau of China.

Traffic and tillage effects on runoff and soil loss on the Loess Plateau of northern China

This paper reports the outcome of 5 years of field plot runoff monitoring, 2 years of water erosion measurement, and a rainfall simulation experiment on moderately sloping farmland on the loess plateau of north-west China. The objective was to test different conservation tillage systems compared with the control treatment, conventional mouldboard plough practice (CK). Tillage, residue cover, and compaction effects were assessed in terms of runoff and soil erosion. Results from the runoff plots showed that conservation tillage, with more residue cover, less compaction, and less soil disturbance, could substantially reduce runoff and soil erosion compared with the control. No tillage with residue cover and no compaction produced the least runoff and soil erosion. Compared with the control, it reduced runoff and soil erosion by about 40% and 80%, respectively. At the start of the experiment, residue cover appeared to be the most important factor affecting soil and water conservation, particularly when antecedent soil moisture was limited. With the accumulation of tractor wheeling effects over the course of the experiment, soil compaction appeared to become a more important factor affecting runoff. Rainfall simulation was then used to assess the effect of non-inverting surface tillage and different levels of residue cover and wheel compaction on infiltration and runoff. This confirmed that wheel compaction effects could be greater than those of tillage and residue cover, at least under the 82.5 mm/h rainfall rate produced by the simulator. The wheeling effect was particularly large when the treatment was applied to wet soil, and severe even after wheeling by small tractors.

Soil physical properties and infiltration after long‐term no‐tillage and ploughing on the Chinese Loess Plateau

Abstract Water is the most limiting factor for crop production in dryland farming. A better understanding of the long‐term impact of tillage and residue management systems on soil structure and water infiltration is necessary for the further development of conservation tillage practice to improve water use efficiency. The objectives of this study were to assess the influence of no‐till with residue retention (NT) and conventional (plough) tillage with residue removal (CT) on soil properties and soil water transmission characteristics in a winter wheat (Triticum aestivum) monoculture system in Shanxi, on the Chinese Loess Plateau. Soil physical parameter measurements were made in the top 30 cm depth in September 2007 after 16 years under the two tillage treatments. Compared with CT treatment, NT significantly (P < 0.05) reduced soil bulk density (7.1%) in the 20–30 cm soil layer, and increased macroporosity (>60 μm, 17.0%) and saturated hydraulic conductivity (249%) in the 15–30 cm soil layer. There were no significant differences in these soil physical properties between tillage systems in the 0–15 cm layer. In addition, plant available water and water infiltration rate were greater in the NT treatment. The improved soil quality parameters and water infiltration from this long‐term experiment indicate that no‐tillage with residue retention is a promising farming system for the dryland farming areas of northern China.

Contribution of farmland wind erosion to sand storms in northern China

China is one of the most arid countries in the world and sand storms happen frequently in northern China and severe storms even impact neighbor countries. Numerous measures such as planting trees, growing grass etc are being used to control sand storms, which has effectively improved ecological environment and controlled the occurrence of sand storms. However, as to the farmland, two kinds of methods are carried out basically. One is planting trees and grass, the other still continues to use traditional moldboard plowed bare cultivation, which led to degradation and desertification of the farmland, reduced the productivity and affected the sustainable development. The soil erosion by wind under conservational and traditional tillage systems was investigated in a 3 years period by means of monitoring field sand losses, wind tunnel simulations and marking pole experiments. The results of the study show that the annual amount of the soil eroded by wind was 6 billion tons in northern China, and the losses of N, P, K and organic matter were 6.67, 1.00, 122.00 and 89.35 million tons, respectively. Among them, the annual soil wind erosion in Beijing was 18 million tons. Compared with tradition tillage, conservation tillage including no till with crop stubble and straw coverage reduced 40% of wind erosion. In order to control sand storms in China, more emphasis should be given to conservation tillage due to its great effectiveness in reducing wind erosion from farmland which is a source of dust, in addition to planting more trees and grasses.

Crop performance as affected by three opening configurations for no-till seeder in annual double cropping regions of northern China

The furrow opening configuration used by no-till seeders can have a major effect on crop emergence in conservation tillage systems. This is particularly important in annual double-cropping regions (winter wheat and summer maize) of northern China where large volumes of residue remain on the soil surface after maize harvesting. This problem has been investigated using 3 different opening configurations for no-till wheat seeding near Beijing in 2004–05 and 2005–06, and assessing performance in terms of soil disturbance, residue cover index, soil cone index, fuel consumption, winter wheat emergence, plant growth, and subsequent yield. In this cropping system, the single-disc opening configuration significantly decreased mean soil disturbance and increased residue cover index compared with the combined strip-chop and strip-till opening configurations, but winter wheat emergence was 6–9% less, probably due to greater levels of residue cover and greater seed zone soil cone index. Winter wheat growth after seeding in combined strip-chop and strip-till seeded plots was faster than that in single-disc seeded plots and mean yield was greater. The most suitable furrow opening configuration in heavy residue cover conditions appeared to be the strip-chop one, which can provide similar crop performance with marginally better fuel economy than the strip-till opening configuration. These results should be seen as preliminary, but they are still valuable for the design and selection of no-till wheat seeders for double cropping in this region of China.

Modeling runoff and soil water balance under mechanized conservation tillage in dry land of north China

PERFECT (Productivity Erosion and Runoff Functions to Evaluate Conservation Techniques), which has been widely used in Australia, is designed to predict runoff, erosion and crop yield under various management pratices including residue, tillage, sequences of plantings, harvesting and stubble managements in dryland cropping areas. The objectives of this study were to modify and calibrate PERFECT to simulate the impacts of tillage, residue and traffic on runoff and soil water balance under conservation tillage of small- to medium-sized machinery, and to assist identifying appropriate conservation practices for sustained crop production in dry land areas of Northern China. The procedure of runoff prediction using USDA Curve Numbers was modified by incorporating the effects of field slope and rainfall intensity. Runoff was calculated daily as a function of rainfall, soil water, residue cover, slope, surface roughness resulted from tillage, and rainfall energy. A simplified Priestley-Taylor equation was employed in the model to calculate potential evapotranspiration, and the effect of residue cover on evapotranspiration was also considered in the model. Input data for the simulation model included daily weather, runoff, soil hydraulic properties, plant available water capacity, cropping systems, and traffic and tillage management. Data were collected from field experiments on Loess Plateau of Northern China. Preliminary results of model calibration and validation showed that the R2 between predicted and observed runoff was 0.86~0.90 and R2 between predicted and observed available soil moisture was 0.82~0.94.