Search

Highlights: [•] The summer crop of maize was the main contributor to annual N2O emissions. [•] DMPP urea was effective in reducing N2O emissions only in the maize season. [•] Applying DMPP urea did not increase yields. [•] Adjusting N fertiliser rates on estimated residual soil N reduced N2O emissions. [•] Severe yield loss can occur if residual soil N is not estimated correctly. [ABSTRACT FROM AUTHOR]

Abstract: Simple plant-based diagnostic tools can be used to determine crop P status. Our objectives were to establish the relationships between P and N concentrations of the uppermost collared leaf (PL and NL) of spring wheat (Triticum aestivum L.) and maize (Zea mays L.) during the growing season and, in particular, to determine the critical leaf P concentrations required to diagnose P deficiencies. Various N applications were evaluated over six site-years for wheat and eight site-years for maize (2004–2006) with adequate soil P for growth. Phosphorus and N concentrations of the uppermost collared leaf were determined weekly and the relationships between leaf N and P concentrations were established using only the sampling dates from the stem elongation stage for wheat and from the V8 stage of development for maize. Leaf P concentration generally decreased with decreasing N fertilization. Relationships between PL and NL concentrations (mgg−1 DM) using all site-years and sampling dates were described by significant linear–plateau functions in both maize (PL =0.82+0.089NL if NL ≤32.1 and PL =3.7 if NL >32.1; R 2 =0.41; P <0.001) and wheat (PL =0.02+0.106NL if NL ≤33.2 and PL =3.5 if NL >33.2; R 2 =0.42; P <0.001). Variation among sampling dates in the relationships were noted. By restricting the sampling dates [413–496 growing degree days (5°C basis) in wheat (i.e., stem elongation) and 1494–1579 crop heat units in maize (i.e., silking), relationships for wheat (PL =0.29+0.073NL, R 2 =0.66; P <0.001) and maize (PL =1.04+0.084NL, R 2 =0.66; P <0.001) were improved. In maize, expressing P and N concentrations on a leaf area basis (PLA and NLA) at silking further improved the relationship (PLA =0.002+0.101NLA, R 2 =0.80; P <0.001). Predictive models of critical P concentration as a function of N concentration in the uppermost collared leaf of wheat and maize were established which could be used for diagnostic purposes. [Copyright &y& Elsevier]

Abstract: The residual effects of pig slurry beyond the year of application have yet to be clearly quantified to determine if it is possible to reduce N fertilizer rates for the subsequent crops. The objective of this study was to assess the residual effects of pig slurry (PSRE) and mineral N fertilizer (MRE) applied to maize (Zea mays L.) with respect to the subsequent wheat (Triticum aestivum L.). A wheat crop was established in the Ebro valley (Northeast Spain) following a 6-year maize monoculture (2002–2007). The maize crops had been annually fertilized with a combination of three pig slurry rates (0, 30, and 50m3 ha−1) and three mineral N rates (0, 100, and 200kgNha−1) commonly applied by farmers in the region. The soil mineral N levels before wheat sowing ranged from 94 to 609kgNha−1 and increased as pig slurry and mineral N applications to maize increased. The PSRE were high and ranged from 2287 to 3796kgha−1 for wheat grain yield and from 36 to 84kgNha−1 for grain-N uptake. Results suggested that the PSRE would mainly originate from the carry-over of unused mineral N. Mineralization of the organic N applied with pig slurry, at rates based on European Union Nitrates Directive, contributed with further residual N effects and would allow farmers to reduce N fertilization of wheat about 30kgNha−1. A reduction in the typical N rates applied to maize along with additional N fertilization of wheat is necessary to maximize crop profitability and reduce the risk of water pollution with nitrates. [Copyright &y& Elsevier]

Abstract: Intensively cropped agricultural production systems should be managed to improve soil quality and ecological processes and ultimately strengthen system capacity for sustained biological productivity. We examined the long-term changes (>20 years) in soil quality and productivity with incorporation of ecological management principles in a set of intensively managed row crop systems of the upper Midwest, USA. Replicated experimental treatments include corn (maize)–soybean–wheat cropping systems under four different management regimes: (a) conventional tillage and fertilizer/chemical inputs (Conventional), (b) no tillage with conventional fertilizer/chemical inputs (No-till), (c) conventional tillage with ∼30% of conventional fertilizer/chemical inputs and a leguminous cover crop (Reduced Input), and (d) conventional tillage with no fertilizer/chemical input and a leguminous cover crop (Organic). Effects of these treatments on soils were compared by developing a soil quality index (SQI) from 19 selected soil health indicators. An old field community maintained in early succession provided a benchmark for comparison. Reduction in tillage or fertilizer (No-till, Reduced Input and Organic) resulted in increased SQI and improved crop production. The No-till (SQI=1.02) and Reduced Input (SQI=1.01) systems outperformed Conventional management (SQI=0.92) in nitrogen availability and use efficiency, soil stability and structure improvement, and microbial nitrogen processing. Improvements in soil quality corresponded with increased primary production and crop yield in these systems, illustrating the value of an ecologically defined SQI for assessing the long-term effects of fertility and tillage management regimes in agricultural production systems. [Copyright &y& Elsevier]

Abstract: Efficiency of fertilizer N is becoming increasingly important in modern agricultural production owing to increasing food requirement and growing concern about environments. However, there is almost no study regarding its long-term efficiency in wheat and maize cropping systems. Long-term (15 years) experiments involving wheat (Triticum aestivum L.) and maize (Zea mays L.) rotations at five field sites with various soil and climate characteristics in China were used to determine the nitrogen (N) efficiency, including the physiological efficiency, recovery efficiency and N mass balance of soil–plant systems in response to different fertilization treatments. The present study consisted of nine treatments: unfertilized, N, phosphorus, potassium, straw and manure or their combinations. The contribution of N fertilizers to wheat yield was higher than to maize and suggested that wheat could be given priority over maize when determining N application rates. Uptake of 1kg N produced 35.6kg of wheat grain and 39.5kg of maize grain. The deficit of N in soils without applied N ranged from 40 to 103kgNha−1 year−1, while N surpluses in soils with applied N fertilizers ranged from 35 to 350kgNha−1 year−1. The apparent accumulated N recovery efficiency (NREac) varied widely from 4% to 90%: unbalanced fertilization and other soil limiting factors (such as aluminium toxicity) were associated with low NREac. In the treatments of combination of N, phosphorus and potassium with normal application rates, the average of NREac in four out of five sites reached 80%, which suggested that best management of N fertilizers could recover most of N fertilizers applied to soils. The results will be helpful to understand the long-term fate of N fertilizers and to optimize the N fertilization for agricultural practices and environment protection. [Copyright &y& Elsevier]

Abstract: In the present study, water and nitrogen interaction on soil profile water extraction and evapo-transpiration (ET) was investigated taking a field experiment on a clay loam soil (Typic Haplustept) at the Indian Agricultural Research Institute, New Delhi with four consecutive crops (maize–wheat–maize–wheat) taken from July 2002 to April 2004. Three levels of water regime, namely W1, W2 and W3 referring to limited, medium and maximum irrigation were applied to each crop depending on the seasonal rainfall and the critical crop growth stage. The three water regimes were used with five nitrogen levels from T1 to T5, (T1, 0% N; T2, 75% N; T3, 100% N; T4, 150% N; T5, 100% N from organic source) in a split plot design for the four crops grown in sequence. Significant water and nitrogen interaction was observed for ET and soil profile water extraction pattern. Averaged across nitrogen treatments, ET in W2 and W3 were higher by 17 and 26%, respectively than W1 in maize 2002 and by 12 and 19% in maize 2003. In case of wheat, ET in W2 and W3 were higher by 27 and 58% than W1 in 1st crop and by 37 and 70% in 2nd crop. The effect of nitrogen regime, however, was prominent in both crops of maize and wheat, with significantly higher profile soil moisture depletion in T4 of each water regime. In all cases, lowest water depletion was observed in control plots receiving 0% N. In both crops, water extraction from surface 60cm was highest in W3 followed by W2 and W1. In maize, the % extraction from 0 to 60cm layer varied from 71 to 76% (W1), 70–79% (W2) and 75–82% (W3), whereas the values for wheat were 70–77, 72–79 and 75–83% for W1, W2 and W3, respectively. The 90–120cm layer contributed only 3–14% to total water extraction in both the crops. From 90 to 120cm layer, higher extraction was observed in W1 as compared to W3. The extraction values in W1, W2 and W3 in maize were 9–13, 7–14 and 3–9, respectively, whereas the corresponding values in wheat were 8–14, 5–12 and 3–7% for the three water regimes. Effect of nitrogen treatments on water extraction from deeper layer was observed with higher extraction in highest fertilized treatment (T4) as compared to other treatments. [Copyright &y& Elsevier]