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Soil organic carbon (SOC), a core soil quality indicator, is influenced by management practices. The objective of our 2012–2016 study was to elucidate the impact of gypsum, crop rotation, and cover crop on SOC and several of its biological indicators under no-till in Alabama (Shorter), Indiana (Farmland), and Ohio (Hoytville and Piketon) in the USA. A randomized complete block design in factorial arrangement with gypsum (at 0, 1.1, and 2.2 Mg/ha annually), rye (Secale cereal L.) vs no cover crop, and rotation (continuous soybean [Glycine max (L) Merr., SS] vs corn [Zea mays, L.]-soybean, both the CS and SC phases) was conducted. Composite soils were collected (0–15 cm and 15–30 cm) in 2016 to analyze microbial biomass C (SMBC), SOC, total N, active C, cold and hot-water extractable C, C and N pool indices (CPI and NPI), and C management index (CMI). Results varied for main effects of gypsum, crop rotation, and cover crop on SOC pools, total N, and SOC lability within and across the sites. Gypsum at 2.2 Mg/ha increased SMBC within sites and by 41% averaged across sites. Likewise, gypsum increased SMBC:SOC, active C, and hot-water C (as indicators of labile SOC) averaged across sites. CS rotation increased SOC, active C, CPI, and CMI compared to SS, but decreased SMBC and SMBC:SOC within and across sites. CPI had a significant relationship with NPI across all sites (R2 = 0.90). Management sensitive SOC pools that responded to the combined gypsum (2.2 Mg/ha), crop rotation (CS), and cover crop (rye) were SMBC, SMBC:SOC, active C, and CMI via SMBC. These variables can provide an early indication of management-induced changes in SOC storage and its lability. Our results show that when SOC accumulates, its lability has decreased, presumably because the SMBC has processed all readily available C into a less labile form.

Made available in DSpace on 2022-04-28T19:46:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Combining deep soil tillage systems with lime application is a potential strategy for improving the sugarcane production in acidic soils. The authors evaluated the influence of tillage systems and lime application on sugarcane performance and soil attributes, including acidity. A field study in a clayey-textured Rhodic Hapludox soil was conducted with sugarcane for two growing seasons utilizing a 3 × 2 factorial scheme comprising three soil tillage systems with and without lime: conventional soil tillage system (CT), deep strip-tillage system (DT) and modified deep strip-tillage system (MDT). The soil tillage systems differed in the depth of soil disturbance and/or lime positioning. In addition to sugarcane stalk and sugar yields, pH, potential acidity (Pac), soil organic carbon (SOC), solid-phase and soil-solution calcium (Ca) and magnesium (Mg), the percentage distribution of exchangeable (%Alex) and non-exchangeable aluminum (%Alne) in the solid phase, and total monomeric (%TM-Al) in soil water extracts were analyzed and determined. The positioning of lime by the different tillage systems influenced the distribution of the Al fractions. TM-Al existed exclusively as organic monomeric Al (OM-Al) and showed little influence from treatments. In contrast, the distribution of Alex and Alne were highly influenced by lime and tillage system and varied according to the tillage efficiency of soil amendment. Soil chemical attributes and yield parameters were also influenced by the treatments in both growing seasons, highlighting the residual effect of liming. The soil chemical attributes influenced the Al fractions. Soil pH and exchangeable and soluble calcium (Caex and Cas) and magnesium (Mgex and Mgs) explained the variation of %Alne. Pac correlated with %Alex, whereas SOC explained the variation of %TM-Al. In general, the sucrose concentration, total recoverable sugar and stalk and sugar yields were increased by lime addition in plant cane and by lime addition and tillage systems in second ratoon. The stalk yield was highest in MDT, whereas the sugar yield was highest in both deep tillage systems. São Paulo State University (UNESP) College of Agricultural Sciences Department of Crop Science, P. O. Box 237 National Soil Erosion Research United States Department of Agriculture São Paulo State University (UNESP) College of Agricultural Sciences Department of Crop Science, P. O. Box 237 FAPESP: 2014/20593-9