Predicting the content of soil mineral nitrogen based on the content of calcium chloride‐extractable nutrients

Abstract

Sustainable management of nitrogen (N) in crop production requires a multifactorial assessment of the soil inorganic nitrogen pool (Nmin). It is assumed that the reliable prediction of the total Nmin content requires data on the content of mineral N forms (NO3‐N, NH4‐N), the contents of other extractable macronutrients and the soil pH. This hypothesis was tested during three growing seasons on a production farm in Górzno, Poland. The contents of 0.01 M CaCl2‐extractable NO3‐N, NH4‐N, P, K, and Mg and the pH were measured in soil layers of 0–0.3, 0.3–0.6, and 0.6–0.9 m just prior to the start of spring vegetation of a given crop and immediately after its harvest (autumn). This study was conducted in 17 fields differing in cropping sequence (CS): 10 with oilseed rape (Brassica napus L.) (OSR‐CS) and seven with maize (Zea mays L.) (SM‐CS) as the dominant crops. Principal factor analysis (PFA) was applied to explore and interpret patterns in data sets defined by the changeability in the content of Nmin in association with variability in contents of other CaCl2‐extractable nutrients. In spring, the first principal factor (PF1) for OSR‐CS was associated with phosphorus (P), whereas PF2 and PF3 were loaded by NO3‐N and NH4‐N, respectively. For SM‐CS, PF1 was loaded by both inorganic N forms, whereas PF2 and PF3 were loaded by potassium (K), magnesium (Mg), and P. In autumn, the dominance of P as the key variable associated with the PFs was stronger in both CSs compared with those in the spring. The prediction of Nmin, in spite of the moderate strength of the PFs (“r” coefficients), can be conducted based on the inorganic N content. In spring, the reliable prediction of Nmin for the OSR‐CS requires data on both N forms. In the SM‐CS, the content of NO3‐N can be used as the sole Nmin predictor. In autumn, the variability in Nmin content can be explained based solely on the NH4‐N content. This was also the main factor affecting the variability in other soil fertility characteristics, such as the contents of K and Mg and the soil pH.

Effect of Digestate on Soil Organic Carbon and Plant-Available Nutrient Content Compared to Cattle Slurry and Mineral Fertilization

“…The applied fertilizers considerably affected the content of NO 3 -N. However, the effect of fertilizers was significantly modified by the year of study. In general, the applied fertilizers, especially digestate and cattle slurry, considerably affected the content of NO 3 -N. In line with the previous observations, this form of N was dominant in soil (80-90%) and well explained the differences in the content of total N min [55]. Since the rate of N in the NPK treatment was higher than in the Dig and Csl treatments, the differences came from a gradual accumulation and mineralization of organic N or remineralization of immobilized manure NH 4 -N [7].…”

Effect of Site Specific Nitrogen Management on Seed Nitrogen—A Driving Factor of Winter Oilseed Rape (Brassica napus L.) Yield

“…The total pool of N, termed as total N input (N int ) is composed of three sub-pools. The first N source, defined in this study as the N input (N in ), comprised two sub-pools of N. The first one, the indigenous N (N i ), is equal to the N mins content in the rooted soil zone in spring [17,21,23]. The N i affects N se on the N-non fertilized plot.…”

“…In some EU countries like Germany and the Netherlands, the N fertilization strategy of crop plants is based on the measurement of the content of mineral N (N min ) before the spring WOSR regrowth [20]. This strategy, as has been documented recently, clearly shows that N use efficiency (NUE) depends not only on the N min content in the root zone, but also on the content of 16 other nutrients, like P, K, and Mg, being responsible for both N uptake, and its utilization by plants [21][22][23][24]. Any shortage of this set of nutrients at the onset of flowering and during the seed filling period (SFP) leads to yield depression [11,25].…”

Spatial Variability of Yield and Nitrogen Indicators—A Crop Rotation Approach

“…The problem of reasonable high soil fertility does not, in fact, refer to the content of P, K or Mg in the topsoil. As it has been recently documented, not only N but also the abovementioned nutrients are taken up from the entire soil profile [24,25,61]. Processes responsible for the N min pool size are quantitatively associated with active pools of other nutrients [24,25].…”

“…The shortage of water in soil affects numerous processes responsible for the release of mineral N from its organic pools. Effective N management is a major challenge to farmers due to temporal, spatial, and vertical variability in plant N uptake [23][24][25][26]. Nitrate N can be taken up by plants even from a soil depth of 150 cm, as has been recognized for some crops such as oilseed rape or maize [27,28].…”