Tillage, fertilization systems and chemical attributes of a Paleudult

Tillage and fertilization methods may affect soil fertility. With the aim of assessing changes in soil chemical properties over a period of ten years, soil samples of a Paleudult were collected over nine seasons at three layer depths (0-5, 5-10, 10-20 cm) and were chemically analyzed. Grain yield and nutrient export in two summer crops, soybean (Glycine max) and corn (Zea mays), in a field experiment set in Eldorado do Sul, in the state of Rio Grande do Sul, Brazil, were determined. Three soil tillage systems were evaluated, conventional (CT), reduced (RT) and no-tillage (NT), combined with mineral (lime and fertilizers) and organic (poultry litter) fertilization. The no-tillage system stood out as compared to the others, especially in the surface layer, in terms of values of organic matter, soil pH, available phosphorus, cation exchange capacity and base saturation. Phosphorus content was higher under organic than mineral fertilization due to the criteria used for the establishment of fertilizer doses. Under organic fertilization, soil pH values were similar to those obtained in limed soil samples because of the cumulative effect of the organic fertilizer. Soybean yield was lower under NT in comparison to the RT and CT systems. Consequently, soybean grain exported a lower content of nutrients than maize grain. Maize yield was not affected by either tillage or fertilization systems.

耕作与施肥措施可对土壤肥力产生影响。本研究以评估十年周期内土壤化学性质变化为目标，于巴西里奥格兰德州南埃尔多拉多（Eldorado do Sul）的田间试验地块中，针对湿润老成土（Paleudult），在九个生长季内采集0~5 cm、5~10 cm、10~20 cm三层深度的土壤样品并开展化学分析；同时测定两种夏播作物——大豆（Glycine max）与玉米（Zea mays）的籽粒产量及养分携出量。试验设置三种土壤耕作体系：常规耕作（CT）、少耕（RT）与免耕（NT），并分别配合矿质施肥（施用石灰与化肥）与有机施肥（禽舍垫料）两种施肥模式。结果显示，免耕（NT）体系较其他耕作体系更具优势，尤其在表层土壤中，其有机质含量、土壤pH值、有效磷含量、阳离子交换量（cation exchange capacity）以及盐基饱和度均表现更优。由于肥料施用量的设定标准存在差异，有机施肥处理下的土壤磷素含量高于矿质施肥处理；同时受有机肥的持续累积效应影响，有机施肥处理的土壤pH值与施用石灰的土壤样品pH值相近。相较于少耕（RT）与常规耕作（CT）体系，免耕（NT）下的大豆籽粒产量更低，因此大豆籽粒携出的养分量低于玉米籽粒。玉米籽粒产量不受耕作方式或施肥体系的影响。