Judith Nyiraneza

Crop yield and soil fertility as affected by papermill biosolids and liming by-products

Ziadi, N., Gagnon, B. and Nyiraneza, J. 2013. Crop yield and soil fertility as affected by papermill biosolids and liming by-products. Can. J. Soil Sci. 93: 319-328. Papermill biosolids (PB) in combination with alkaline industrial residuals could benefit agricultural soils while diverting these biosolids from landfill. A greenhouse study was conducted to evaluate the effect of three types of PB at rates of 0, 30, and 60 wet Mg ha-1, as well as five liming by-products at 3 wet Mg ha-1 along with 30 Mg PB ha-1 on crop yield, nutrient accumulation, and soil properties. De-inking paper biosolids (DB, C/N of 65) were applied to soybean [Glycine max (L.) Merr.], and two combined PB (PB1, C/N of 31; and PB2, C/N of 14) were applied to dry bean (Phaseolus vulgaris L.) and barley (Hordeum vulgare L.), respectively. The liming by-products included lime mud (LM), wood ash (WA) from paper mills, commercial calcitic lime (CL), Mg dissolution by-product (MgD), and Mg smelting and electrolysis work (MgSE). Compared with the control, PB2 increased barley yield and total Mg and Na accumulation, and both PB increased plant N, P, and Ca accumulation in barley and dry bean. The impact of DB on soybean was limited. The addition of liming by-products to PB or DB did not affect crop attributes except the combination with MgSE, which severely reduced the growth of dry bean and, to a lesser extent, soybean. Soil NO3-N was immobilized following DB application, whereas there was a net release with both PB. Combining PB and liming by-products produced the greatest changes in soil properties at harvest. Generally, LM and CL raised pH and Mehlich-3 Ca, and MgSE caused a strong increase in Mehlich-3 Mg and Na and water-soluble Cl. When used with appropriate crops, biosolids from paper mills and alkaline residuals other than MgSE can efficiently enhance soil fertility by providing organic C and macronutrients for balanced crop fertilization.

Changes in soil organic matter over 18 yr in Prince Edward Island, Canada

Abstract: Soil fertility decline is encountered in intensively managed low-residue systems. This long-term study (1998–2015) characterized soil organic matter (SOM) changes in the province of Prince Edward Island (PEI), Canada. The sampling locations were based on the 4 km × 4 km National Forest Inventory grid. Five subsamples were collected within a radius of 1–6 m from the centre location at the intersecting points on the grid and at locations 100 m in each cardinal direction covering the whole province every 3 yr, for a total of six cycles. The interpolation used the regression kriging method. Means ranged from 2.8% to 3.6%, coefficients of variation ranged from 0.22 to 0.28, and residual nugget and sill values were 0.03 and 0.06, respectively. From cycle 1 to cycle 6, acreage with 2%–3% SOM increased from 10% to 73% of the total area, acreage with 3.1%–4% SOM declined from 70.6% to 24% of the total area, and acreage with >4% SOM declined from 19% to 0.8% of the total area. Areas with a history of intensive agricultural activity were associated with the lowest SOM levels (2%–3%) at the beginning of the study, and SOM levels in those areas either remained unchanged or declined (<2%) at the end of the study, suggesting a predominance of recalcitrant SOM fractions with a longer turnover rate. This long-term study highlights the need to put in place strategies to increase levels of SOM to sustain PEI soil productivity.

The Benefits of Crop Rotation Including Cereals and Green Manures onPotato Yield and Nitrogen Nutrition and Soil Properties

Soil quality decline is a common concern in potato production systems. Including cereals and green manures (GMs) in potato rotation could improve soil productivity and sustain potato (Solanum tuberosum L.) yields and quality. This experiment initiated in Quebec, eastern Canada, assessed the effects of two cycles of 2-yr potato rotations with cereals and GMs on soil properties and potato yield and quality, and on disease incidence from 2008 to 2011. Three cereals [corn (Zea mays), barley (Hordeum vulgare), and oat (Avena sativa)] seeded in spring, three summer GMs [mustard (Sinapsis alba), japanese millet (Setaria italica), and pearl millet (Pennisetum glaucum)], four fall GM crops [oat, mustard, wheat (Triticum aestivum), and rye (Secale cereale)], and continuous potato (Solanum tuberosum L.) were grown on main plots in 2008 and 2010. In following years (2009 and 2011), each main plot was split, and five N fertilizer rates (0, 50, 100, 150 and 200 kg N ha-1) were applied to potato. After two rotation cycles in 2011, soils under cereals and summer and fall GMs had higher soil water-extractable organic C and N contents, nitrate levels, soil respiration, urease and dehydrogenase activities, and a larger proportion of soil macro aggregates (0.25 to 2 mm), compared with the continuous potato. Cereals and summer GMs increased marketable potato yield and specific gravity, whereas fall GMs increased tuber yield but reduced tuber quality. In addition, fall GMs favored the incidence of common scab and black scurf. Summer GMs had higher potato N uptake and N efficiency compared to cereals and fall GMs. Although fall GMs produced higher net returns than cereals and summer GMs, they may not represent a viable long term option to sustain potato production and to enhance soil quality. Results indicated that growing cereals or summer GMs in rotation with potato is an interesting alternative to improve soil properties while sustaining potato yield and quality. A fall GM with a better growth during the fall season may sustain potato yield and quality, if included in longer potato rotation, but this remains to be determined.