Research and farmers' experiences have demonstrated that reduced tillage helps maintain surface residues and provide substantial benefits in terms of water use efficiency, soil condition and productivity. However, the impact of field traffic and its influence on the soil when tillage is reduced or eliminated have been ignored, for small to middle-sized machinery are mostly used in Chinese agriculture. There is a need to study on wheel traffic impacts and to test controlled traffic farming system for Chinese conditions. This paper reports the five-year controlled traffic conservation tillage experiment in North China. Two trial plots (Spring Maize and Winter wheat) with four treatments and five replications were set up. The results indicated that controlled traffic conservation tillage could minimize the compaction of wheel traffic, make field operation timely and precisely, improve soil structure and increase soil moisture on crop zone which is beneficial to crop establishment and growth. With the accumulation of damages year after year, the impacts of random wheeling are becoming more notable. Heavier machinery appeared to compact soil to a greater depth, but even small tractors could compact the surface 10cm, critical to rainfall infiltration, to a remarkable degree. For the small-scaled controlled traffic system tested in this study, traffic lanes occupy about 20% of the land, but the yields were similar to those in the non-controlled traffic fields. Further test is needed for the long-term impacts of the traffic lanes on soil structure and crop yield and detailed analysis is necessary to develop a suitable controlled traffic farming system.
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 R<sup>2</sup> between predicted and observed runoff was 0.86~0.90 and R<sup>2</sup> between predicted and observed available soil moisture was 0.82~0.94.
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.