Strip-till and no-till soybean growth and distribution of roots and soil phosphorus, potassium, and water with broadcast and subsurface-band fertilization

摘要

Method of application of the slowly-mobile nutrients phosphorus (P) and potassium (K) in conservation tillage systems were little mixing of the soil occurs, is an important management decision as placement can influence the availability to these nutrients to the crop. The objectives of this study were to determine the effect of no-till, strip-till, and P and K rate and placement on soybean [Glycine max (L.) Merr.] root distribution, shoot growth and nutrient accumulation, seed yield and seed composition; and to quantify treatment effects on the distribution of P, K, and water in the soil. A three-year field experiment was conducted in Champaign, Illinois on Flanagan silt loam and Drummer silty clay loam soils with tillage and fertilizer placement as the main (whole) plot: no-till broadcast (NTBC), no-till deep band (NTDB), and strip-till deep band (STDB) with deep banding at 15 cm. The split-plot consisted of four P application rates (0, 12, 24, 36 kg P ha-1 yr-1) and the split-split plot consisted of four K application rates (0, 42, 84, 168 kg K ha-1 yr-1). Vegetative samples were taken throughout the growing season to measure various growth components. Roots and soil P, K, and water were measured periodically during the season at in-row (IR) and between-rows (BR) positions. Seed yield and yield components were measured at harvest and seed was analyzed for oil, protein, P and K concentration. Seed yield for STDB was 3.06 Mg ha-1 and 10 % greater than NTBC and 7 % greater than NTDB. At the same time, NTDB produced a small but significant 0.1 Mg ha-1 (4%) greater yield than NTBC. Initial soil P levels were marginal for soybean production and P fertilization in the no-till systems increased yields. However, STDB produced consistently higher yields than the no-till systems and showed no response to P fertilization. Soils had adequate starting K fertility and additional K produced no yield increase. Deep banding increased P and K test level beneath the row and lowered soil surface test-values compared to broadcast applications. Since seed yield is not reduced and subsurface banding of fertilizer reduces fertility levels on the soil surface, this placement method may be a viable option for soybean production in fields where high potential for surface P runoff presents an environmental concern. There was no root proliferation in response to the concentrated band of fertilizer. Regardless of treatment, soybean root densities were greatest within the top 10 cm of the soil. Throughout the growing season there was greater water availability in the top 10 cm of the soil at the BR position in STDB than in the no-till systems (NTBC and NTDB). This was likely the result of a combination of greater water infiltration with strip-till and the crop residue present in the BR position that diminished the potential for the infiltrated water to evaporate. The top 10 cm of the soil at the BR position also had the greatest change in soil P for all tillage/placement systems, likely as result of crop uptake. Within the top 10 cm of the soil at the BR position STDB also had smaller root density than NTBC at the R3 development stage. Greater nutrient accumulation with a smaller root system in STDB relative to NTBC indicate that overall STDB provided improved conditions for nutrient uptake, possibly as a result of greater water availability. Above-ground dry biomass was consistently higher for STDP than NTBC especially during the late vegetative/early reproductive stage to about R4 development stage. Similarly, STDP produced greater plant height, leaf area index (LAI), and crop growth rate (CGR) compared to NTBC. These findings indicate that STDP is advantageous compared to the no-till systems for soybean production.