Quantifying soil water conservation in the semiarid region of Saskatchewan, Canada: Effect of fallow frequency and N fertilizer

Abstract

Soil water is the most limiting factor influencing crop production in the semiarid prairies. The effects of fallow frequency and nitrogen (N) fertilization on soil water conservation were quantified for a 40-yr (1967–2006) field experiment conducted on a medium textured Orthic Brown Chernozem (aridic haploboroll) in semiarid southwestern Saskatchewan, in which soil water contents were measured each year in early spring (generally a week prior to seeding), shortly after harvest, and again just prior to freeze-up in the fall. The three treatments examined were continuous spring wheat (Triticum aestivum L.) (Cont W) and fallow-wheat (F-W), each receiving recommended rates of N and P fertilizer, and Cont W receiving only P. On average, 36% of the precipitation received during the fall and winter months for Cont W (N + P) was conserved in the soil. In the summer fallow system [F-W (N + P)] a greater proportion (42%) of the precipitation was conserved during the first fall and winter. Despite the fact that cumulative precipitation from spring to late fall during the fallow period averaged 243 mm, compared with 152 mm received during the previous fall and winter period, the amount (31 mm) and proportion (13%) of precipitation conserved was considerably less than that during the first overwinter period. These differences were attributed mainly to much higher summer evaporative losses. During the second overwinter period, only 6% of the precipitation received was conserved in the F-W (N + P) system compared with 44% in the first overwinter period. This poor conservation during the second winter was thought to be related to increased snow blowoff due to smaller amounts of standing crop residues, and to the freezing of a wet and bare soil surface, restricting water entry during snowmelt or spring thaw events. Physical based soil-crop models, which must be first improved for overwinter simulations, should be tested on the current data set to further interpret the observations and hypotheses. Compared with the 36% of fall and winter precipitation conserved in Cont W (N + P), inadequate N fertility [Cont W (+ P)] resulted in only 27% of the precipitation being conserved during this period. At harvest, F-W (N + P) and Cont W (N + P) had similar amounts of water in the soil, but Cont W (+ P) had significantly (P < 0.05) more because of reduced water use. However, by the following spring soil water recharge being proportional to crop residues produced resulted in F-W (N + P), Cont W (N + P) and Cont W (+ P) having 252, 209 and 204 mm/1.2 m soil, respectively. Equations were developed that will allow estimation of water conserved as a function of precipitation received between harvest and seeding for F-W (N + P) and Cont W (N + P) (R2 = 0.52*** in each case). Trends in grain yield were fairly closely correlated with growing season precipitation and potential evapotranspiration [squared semipartial correlation coefficients for Cont W (N + P) 0.32 and 0.17, respectively, and for F-W (N + P) 0.35 and 0.12]; soil water conservation played a minor role in determining final grain yields (squared semipartial correlation coefficient < 0.08). Key words: Soil water, spring wheat, precipitation deficit, yield trends, water conserved trends

Farming tactics to reduce the carbon footprint of crop cultivation in semiarid areas. A review

“…However, a higher frequency of summerfallow decreased the annualized yield of the system. The increased grain yield of the wheat crop grown after summerfallow, compared with wheat after wheat, did not overcome the lost opportunistic yield in the summerfallow phase (De Jong et al 2008;Campbell et al 2008).…”

Diversifying cropping systems enhances productivity, stability, and nitrogen use efficiency

“…The variability in annualized grain and protein yield across years was not surprising, given that the study area is a moisture‐limiting environment. Several studies have highlighted the critical importance of precipitation and soil moisture in this and other semiarid regions (Campbell et al., ; De Jong et al., ; Franco et al., 2018, Kirkegaard & Hunt, ; Kröbel et al., ). Moreover, studies have indicated that crop yield in this region is affected more by precipitation during the growing season than preplant residual soil water (De Jong et al., ; Gan et al., ).…”

“…() found that GM did not reduce soil water relative to summer fallow. It must be noted that precipitation during the growing season may have a more dominant role in affecting crop yield compared to water availability in early spring (De Jong et al., ; Gan et al., ). Our findings could also be linked to the relatively low biomass produced by the GM crop (Zentner et al., ), resulting in little biomass cover to trap snow and conserve soil moisture in the subsequent growing season by reducing evapotranspiration.…”

Diversifying crop rotations with pulses enhances system productivity

“…Rainwater during the growing season plays a much more important role in determining crop yield than pre-planting residual soil water 35,36 . 8,36,37 such as evaporation (which is typically greater than 1500 mm annually at the experimental area) and evapotranspiration.…”

“…8,36,37 such as evaporation (which is typically greater than 1500 mm annually at the experimental area) and evapotranspiration. However, the main difference between the summerfallow systems and the diversified system with pulses in terms of water use occurs during the period of 1 May to 31 August in Year-2 of the cropping sequence, where 79% of the un-conserved rainwater by the summerfallow system can be utilized for grain production through the adoption of the alternative, non-summerfallowing pulse systems.…”