2.1. Collection and screening of data
To check the effect of fallow tillage methods on soil and plant parameters in winter wheat and spring maize cropping systems, we carried a search in peer-review journals from 1973 to 2022 in Google Scholar and Web of Science with keywords SWS, PSE, WUE, ET, wheat and maize as affected by CT, NT, RT and ST. Initially 845 publications were collected and screened by following criteria:
i. Tillage methods should be tested in the field cropping systems. In every study, conventional tillage (CT) should be used as the control treatment. The NT, RT and ST should be compared with CT.
ii. Experiments that are completely dependent on natural precipitation should be selected and the irrigation should not be applied at any point throughout the experimentation such as only precipitation should serve as the source of moisture.
iii. Simulation and model studies were not included.
The table 1 provides a brief introduction to tillage techniques. 1. Fig. 1 shows the geographic details of 119 trial sites around the globe. The data collection, partition and selection has shown in Figure 7. The literature compares several conservation tillage techniques against conventional tillage during fallow.
2.2. Creation of database
The data were homogenized into groups based on the various tillage techniques. Mean annual air temperature (MAT) was split into three categories: > 15 °C, 8-15 °C, and 8 °C. Mean annual precipitation (MAP) was divided into three categories: > 600 mm, 400-600 mm, and 400 mm. There are three broad categories for soil texture (fine, medium and coarse). We manually estimated PSE when PSE was not calculated in the publications, but the SWS with fallow precipitation was present (Nielsen and Vigil 2010). If the study did not contain information on latitude and longitude and weather, we collected these observations from an online search engine (https://www.whatsmygps.com). GetData graph digitizer 2.20 software (http://getdata-graph-digitizer.com/index.php) was used to extract data from the figures. The soil texture ranged from fine to coarse, the MAP ranged from 141 to 830 mm, whereas the MAT ranged from 4.1 to 22.1°C. We estimated the standard deviation (SD) value using the following formula by using the standard error (SE) value:
\(SD=SE\ \times\ \sqrt{n}\) (1)
Where “n” represents the number of samples.
Possibly, we collected data on climatic and geographical conditions including longitude and latitude, fallow and annual precipitation, annual temperature, altitude, experimental location and duration of experiment and publication years.