Effects of continuous straw return to soil on maize growth and soil chemical and physical characteristics

As it significantly improves the physical and chemical characteristics of farmland plow layer soil, straw return is an efficient strategy to enhance soil fertility. To understand the effects of different straw return methods on soil fertility and maize growth, experiments were conducted from 2002 to 2010 in Pingliang Maize Breeding Experimental Station (PMBES) of Gansu Agricultural University. Soil chemical and physical characteristics, and maize plant root growth and yield were determined for three straw return treatments — 3-year straw return (H3, 2007—2010), 6-year straw return (H6, 2005—2010) and 9-year straw return (H9, 2002—2010) — and non-straw return used as the control (0-year straw return, CK). The results showed that soil contents of organic matter, total nitrogen, total phosphorus, alkali-hydrolysis N and available K in the 0~30 cm soil layer significantly improved with increasing years of straw return. Soil bulk density reduced significantly in the 20~50 cm soil layer with increasing years in the order of 9 < 6 < 3 < 0 years. Root weight density, total length and activity significantly improved with increasing years of maize straw return. Especially during later growth stage, maize root characteristics in deep soil exhibited significant differences among different straw return treatments. Root activity in the 40~60 cm soil layer in H9, H6 and H3 treatments were higher than in CK treatment by 54.8%, 29.1% and 16.3%, respectively. Root weight density and total length in H9 treatment increased respectively by 44.3% and 79.3% over CK. The root weight density and total length increased by 30.8% and 58.9% in H6, and by 18.8% and 47.7% in H3 treatments over CK, respectively. Under CK, maize root rapidly recession in the fields. Plant height, ear height of maize increased with increasing years of straw return. Ear height of H9, H6 and H3 was 11.1 cm, 5.3 cm and 0.7 cm higher than that of CK respectively. The maize yield improved with increasing years of straw return too. 100-seed weigh and yield of H9, H6, H3 increased by 17.4%, 10.2%, 7.5%, and 15.4%, 10.3%, 4.5%, respectively, over the CK. The findings suggested that straw return delayed root consenescence, enhanced root nutrient uptake at the later growth stage and increased maize yield.