خاکورزی و مدیریت پسماند اثرات آن بر ویژگی های خاک و راندمان محصولات ذرت و گندم دیم در آب و هوای نیمه گرمسیری و مرطوب

Minimum tillage in conjunction with crop residue mulch may be a promising practice of soil management to improve soil properties and crop production in the subtropical climate of north-western Punjab. Therefore, a 5-year field experiment was conducted to study the effect of tillage and crop residue mulch on some properties of a sandy loam soil (Fluvisol) cropped to rainfed maize (Zea mays L.)–wheat (Triticum aestivum L.) sequence. Three main treatments investigated were minimum tillage (consisting of making a small trench for seed placement) with 3 Mg ha−1 crop residue mulch of the previous crop (MTR), minimum tillage without residue mulch (MT), and conventional tillage (involving two diskings followed by a planking) without residue mulch (CT). Subtreatments consisted of five rates of fertilizer N (0, 40, 80, 120 and 160 kg ha−1) applied to wheat. Maize received 80 kg N, 17 kg P and 16 kg K ha−1. Soil quality in terms of increased organic matter content, water retention, infiltration of water and aggregation, and decreased bulk density of the surface soil was improved in the MTR relative to other treatments. Pooled grain yield in the MTR treatment remained below the CT treatment during the first 2 years (1993 and 1994) but was subsequently greater than the CT. However, grain yield in the MT treatment was lower than CT treatment throughout the study period. The results indicated the necessity of using residue mulch in conjunction with minimum tillage in order to improve soil quality and sustain/improve crop production.

A large tract (0.32 million ha) of productive alluvial soils lies in the north-western Punjab, India. This area, called “Kandi area”, receives mean annual rainfall from 750 to 1150 mm. In spite of adequate climatic conditions, crop yields are rather low. Singh et al. (1983) reported average yields of 1620 kg ha−1 for maize and 1760 kg ha−1 for wheat on farmer’s fields. The reasons responsible for the low yields include excessive runoff and soil erosion, low soil fertility, low groundwater availability, erratic rainfall distribution and low inputs. In order to ameliorate some of these limitations to crop production, a sound management system for these soils needs to be developed. Since these “Kandi” area soils are poor in organic matter, which is a primary parameter to evaluate soil quality, it is essential that an alternative tillage practice will increase organic inputs. In temperate regions, the no tillage or minimum tillage concept of soil management has been adopted with some success. Working on the tropical soils of Nigeria, Lal (1976) reported that this practice in conjunction with crop residue mulch improved soil quality and crop yield by increasing infiltration of water into soil profile and lessening water runoff and soil erosion. Minimum tillage practices are considered as an important component of sustainable rainfed farming (Carter, 1994; Papendick and Parr, 1997). The system is thought of enhancing soil quality (Steiner et al., 1988). Crop residue mulch improved soil quality in terms of organic carbon and biotic activity (Karlen et al., 1994). An increase in infiltration of water into soil has also been reported by Bruce et al. (1992). However, little work has been done on these aspects for the “Kandi” soils. The present study investigated the effects of tillage and crop residue mulch on soil quality and grain production in a maize (Zea mays L.)–wheat (Triticum aestivum L.) rotation on an alluvial soil in the “Kandi” area of the Punjab in a subhumid subtropical climate.

Compared to CT, MTR proved to be a promising alternative soil management practice to improve and sustain higher yields of rainfed maize and wheat in a subhumid subtropical climate. This practice also improved soil quality by increasing organic carbon, aggregation, infiltration rate and soil water retention, as well as decreasing bulk density near the soil surface. However, under this practice a 2-year lag period was required to adjust to the new management conditions. Further research is needed to overcome this yield lag of 2–3 years in the minimum tillage system.