Organic materials returning to field and deep tillage improving chemical properties of calcic chernozem and increasing crop yield

Abstract: Calcaric chernozem is widely distributed in the mid-western area of Songnen Plain in Heilongjiang Province, China, and it occurs along with carbonate carbonate saline-alkali soil. There are many sodium ions or bicarbonate ions in this kind of soil, and the pH value of the soil is high, more than 8.2, which limits plant growth. The Songnen Plain is located in the semi-arid area and the annual precipitation is less than 500 mm; soil evaporation is more than precipitation in dry season, and a large number of sodium ions (Na+) and bicarbonate ions (HCO3-) rises up to the soil surface with soil capillarity and crystallization on the soil surface as the secondary soil salinization, which limits plant growth and its yield. Many researches have been reported for the improvement of this calcareous chernozem, but they are only concentrated with the reduction of soil pH value. We are here concerned with the returning of crop residue into subsoil as organic matter, proper crop rotation and cultivation technics. A test field was constructed in Anda, Songnen Plain, Heilongjiang Province. This paper dealt with the chemical properties with different deep tillage technics such as pH value, base cations, soil nitrogen (N), phosphorus (P) and potassium (K). We tested 3 kinds of deep tillage technics: deep loosing (DL), tillage with straw return in subsoil (TSR) and tillage with straw and chicken manure return in subsoil (TSCR), and the fields here were generally tilled by traditional powered rotary (CK). Each test field was 2 800 m2, and TSR and TSCR were cultivated by our soil displacing plough. The main results showed that the pH value and the contents of water-solution K+, Na+ and HCO3- decreased, and Ca2+ increased in each test field of deep tillage, water-solution Na+, HCO3- and pH value in soil had significantly positive correlation, water-solution Ca2+ and pH value had significantly negative correlation; N, P and K increased in deep soil layers, soil available N, P and K in the deep tillage were greater than those in CK in 20-50 cm depth, the order was TSCR?TSR?DL?CK, and the effect of TSCR treatment was the strongest on the soil N, P and K; and the corn yield significantly increased. The increase of the crop yield under the TSCR continued for 3 years, in the first year, the crop yield increased by 47.1% and in the second year, 25.2% and in the third year 24.7% respectively, and 32.3% was the average value for the 3 years. The effect of TSR was less than that of TSCR and in first year, and the increase of crop yield was 11.2%, 9.8% in the second year and 18.1% in the third year respectively, with the average value of 11.3% for the 3 yields. The effect of the DL treatment was the poorest and the increase of crop yield was zero in the first year, 6.3% in the second year and 14.3% in the third year respectively, with the average value of 6.2% for the 3 years. As a result, the TSCR was the most suitable for Calcic Chernozem.