Short-Term Effects of Tillage Practices on Soil Organic Matter of a Clay Loam Soil in Northeast China.
Xiaoping Zhang, Aizhen Liang, and Huajun Fang. Northeast Institute of Geography and Agri-ecology, 3195 WeiShan Road, Gaoxinkaifa District, Changchun, 130012, China
Our tillage study was initiated in fall 2001 at the Experimental Station (44°21'N, 148°150'E) of Northeast Institute of Geography and Agricultural Ecology (the Chinese Academy of Sciences) in Dehui county, Jilin Province of China. The study site lies in Temperate Zone with a continental monsoon climate. The mean annual temperature is 4.4 ºC and the mean annual precipitation is 520.3 mm with more than 70% occurring in June, July and August. Soil is a clay loam (Typical Hapludoll) and some selected physical and chemical characteristics are presented in Table I. Prior to the establishment of this tillage trial, the land had been used for continuous maize production under conventional tillage management for many years (> 10 years). Tillage experimental trial, consisting of moldboard plow (MP), ridge tillage (RT), and NT, was a randomized complete block design with four replicates. Each tillage plot was split into two sub-plots (5.2 m X 20 m) which were under maize-soybean rotation with both crops present at each year. Moldboard plough included one fall moldboard ploughing (about 20 cm deep) after maize harvest and spring disking (7.5 to 10 cm deep) and field cultivation. Ridge-tillage included ridging in June and smashing maize stalk/roots in fall (less than 1/3 row width). The NT soil had no soil disturbance except for planting using a KINZE-3000 NT planter (Williamsburg, Iowa). Except for the plots under MP practices, all the crop residues were retained on soil surface. Each year, 100 kg ha-1 N was applied to maize as starter fertilizer and 50 kg N ha-1 as top dressing at the V-6 stage for maize, respectively. In addition, 45.5 kg P per ha and 78 kg K per ha were also used to maize as starter fertilizers. The starter fertilizers for all plots were applied concurrently during the planting. For soybean, all fertilizers were applied as starter fertilizer, including 40 kg N per ha, 60 kg P per ha, and 80 kg K per ha. Composite soil samples (7 sub-samples per plot) were collected down to a depth of 30 cm after harvest (corn phase) in 2001 and 2004. The samples were taken using a hand auger (2.64 cm diameter) (Jia et al., 1995) which allowed separation of each soil core into 4 segments without soil compaction, including 0-5, 5-10, 10-20, and 20-30 cm. Soil samples were gently broken and air-dried and weighed. After manually removing visibly identifiable crop residues, the soil was ground to pass a 0.25 mm sieve. A sub-sample, dried at 105 °C, was used to calculate water content. The bulk density of soil samples was calculated using the inner diameter of the core sampler and segment depth, and the oven-dry weight of the core samples. Total soil C was determined using a FlashEA1112 Elemental analyzer (Thermofinnigan, Italy). Since the soil was free of carbonates, soil organic C was assumed to equal the total C. Soil organic carbon storage was presented on an equivalent soil mass based approach. Results indicated that NT practices did not lead to significant increase of SOC at top soil (0-5 cm) compared with MP and RT practices, however, the SOC content in NT soil was noticeably reduced at a depth of 5-20 cm. Accordingly, short-term (3-y) NT management tends to stratify SOC concentration but not necessarily increase its storage in the plow layer for this black soil. Three years of no-tillage management tended to stratify SOC concentration but not their storage in the plow layer on this clay loam soil. The use of no-tillage practices on this fine-textured and poor-drained black soil might not sequester more SOC than conventional tillage.