Data on initial leaf P concentrations and final dry matter yields of silage maize in response to row-injected cattle slurry

This article displays a dataset obtained in a field trial conducted in 2016 on a sandy loam and a coarse sandy soil, Denmark. Leaf phosphorus (P) and nitrogen (N) concentrations at the five-leaf stage (V5) and final dry matter (DM) yields of silage maize were determined in response to seven treatments with placed slurry below the maize row. Two row-injection methods combined with slurry acidification or addition of a nitrification inhibitor were tested. Furthermore final crop P uptake and P surplus at field level were determined. This dataset can be used to assess the effect of placed slurry with or without slurry acidification and addition of a nitrification inhibitor on silage maize yields and to enhance our knowledge on maize P uptake and P surpluses at field level. In turn this can support the design of appropriate row-injection machinery of slurry. The data supplied in this article is related to the research article entitled “Row-injected cattle slurry can replace mineral P starter fertiliser and reduce P surpluses without compromising final yields of silage maize” [1], where results from 2017 and 2018 are presented and discussed. The trials in 2016, 2017 and 2018 were conducted on the same study sites. The experimental design in 2017 and 2018 was a full-factorial design and did also include reference treatments with evenly injected slurry, whereas these reference treatments were not included in the present article.


a b s t r a c t
This article displays a dataset obtained in a field trial conducted in 2016 on a sandy loam and a coarse sandy soil, Denmark. Leaf phosphorus (P) and nitrogen (N) concentrations at the five-leaf stage (V5) and final dry matter (DM) yields of silage maize were determined in response to seven treatments with placed slurry below the maize row. Two rowinjection methods combined with slurry acidification or addition of a nitrification inhibitor were tested. Furthermore final crop P uptake and P surplus at field level were determined. This dataset can be used to assess the effect of placed slurry with or without slurry acidification and addition of a nitrification inhibitor on silage maize yields and to enhance our knowledge on maize P uptake and P surpluses at field level. In turn this can support the design of appropriate rowinjection machinery of slurry. The data supplied in this article is related to the research article entitled "Row-injected cattle slurry can replace mineral P starter fertiliser and reduce P surpluses without compromising final yields of silage maize" [1] , where results from 2017 and 2018 are presented and discussed. The trials in 2016, 2017 and 2018 were conducted on the same study sites. The experimental design in 2017 and 2018 was a full-factorial design and did also include reference treatments with evenly injected slurry, whereas these reference treatments were not included in the present article.
© 2020 The Author(s

Value of the data
• The data is useful to assess the effect of different slurry row-injection techniques on silage maize yields grown in humid temperate regions. • Other scientist studying slurry management and maize cropping can benefit from these data, when dealing with studies on crop growth in response to placed slurry. Furthermore, phosphorus crop uptakes and balances are provided, and these data can be used to assess crop phosphorus demands and phosphorus accumulation in soil. • The data can be used to develop appropriate slurry-injection machinery in order to improve the utilization of slurry nutrients. • The data offers information on maize yield in two additional trials conducted in 2016 related to [1] , where data from 2017 and 2018 are presented. Table 1 presents soil properties for each field at the two experimental sites in 2016. Monthly precipitation and temperature are provided for 2016 at the two study sites ( Table 2 ).   Table 3 Treatment overview showing experimental combinations of slurry application method, nitrification inhibitor (NI), slurry acidification (SA) and mineral starter N and P application. GF: Goosefoot tine with a 26-cm broad tine at 10 cm or 17 cm depth with a tine distance of 75 cm. S-spring tine: 6-cm wide S-spring tine at 10 cm depth with a tine distance of 37.5 cm.

Slurry properties, overview of treatments and main field operations
Overview of the treatments and their abbreviations are presented in Table 3 . Slurry properties and slurry application rates are provided in Table 4 , and dates for main field operations for 2016 are given in Table 5 .   Table 6 Leaf phosphorus (P) and nitrogen (N) concentration at the five-leaf stage (V5). Different letters within columns denote statistically significant differences (Tukey, P < 0.05). NB: Narrow band injection, BB: Broad-band injection, SA: slurry acidification, NI: Nitrification inhibitor. The two highest P and N concentrations for each location are indicated by bold numbers.  Table 6 presents the P and N concentration at five-leaf stage (V5). At Foulum, the lowest leaf P concentration at V5 was observed when the broad-banded (BB) slurry was placed at 17 cm depth (BB untreated 17cm). The highest P concentrations were observed when a nitrification inhibitor was added to the slurry or when the slurry was acidified in combination with placement Table 7 Maize dry matter (DM) yield, P uptake and P surplus at harvest for Foulum and Havris. Different letters within columns denote statistically significant differences (Tukey, P < 0.05). NB: Narrow band injection, BB: Broad-band injection, SA: slurry acidification, NI: Nitrification inhibitor. The two highest DM yields for each location are indicated by bold numbers.  Table 6 ). At Havris, the lowest leaf P concentrations at V5 were observed when the slurry was placed in broad bands at 17 cm depth (BB untreated 17cm). The highest leaf P concentration at V5 was observed when acidified slurry was placed in broad bands (BB + SA). Table 7 presents the DM yield and P uptake at harvest and the P surplus defined as P applied with cattle slurry minus P exported with the crop. At Foulum, treatments where slurry was placed in narrow or broad bands at 10 cm depth in combination with slurry acidification or a nitrification inhibitor (NB + SA, NB + NI, BB + SA and BB + NI) provided the highest DM yields. In these particular treatments, the DM yields were on average 1.5 Mg DM ha −1 higher than the DM yield observed in the treatment where slurry was placed in a broad band at 17 cm depth (BB untreated 17cm). At Havris, no significant treatment effect on DM yield and P uptake at harvest was observed.

Initial leaf P concentrations and final dry matter yields of silage maize
Figs. 1 and 2 present the relation between leaf P and N concentrations and final DM yield at harvest for each of the experimental sites.

Experimental design
A field experiment was established in 2016 on two soil types: a sandy loam at Foulum and a coarse sand at Havris in Central Jutland, Denmark ( Table 1 ). The Foulum soil is classified as a Typic Hapludalf and the Havris soil as a Typic Haplorthod according to the USDA Soil Taxonomy System. The climate is temperate and humid ( Table 2 ). The experiment was organized as a randomized block design with four replicates and seven treatments ( Table 3 ). The plot size was 18 × 3 m (encompassing four rows), and the harvest plot size was 18 × 1.5 m (two middle rows).

Row-injection of slurry
Following ploughing, cattle slurry ( Table 4 ) was row-injected at an application rate of 100 kg slurry-NH 4 + -N ha −1 . Slurry was injected below the maize row with a 26-cm broad goosefoot tine with a tine distance of 75 cm (BB row-injection) at 10 or 17 cm depth from the soil surface to the bottom part of the slurry band, or with a 6-cm S-spring tine with a tine distance of 37.5 cm (NB row-injection). For treatments applied with acidified slurry, acidification was carried out in the slurry tanker by adding 13 L 7.08 M sulfuric acid (AcidLine R , DanGødning, Fredericia, Denmark). For treatments receiving slurry with a nitrification inhibitor, 3.4-dimethylpyrazole phosphate (DMPP) was added in the slurry tanker as Vizura (BASF, Ludwigshafen, Germany) with an application rate of 2 L ha −1 . Treatment overview is presented in Table 3 . 20 kg mineral N ha −1 (as ammonium sulphate nitrate) was placed at the time of sowing in all treatments. In addition, a supplementary broadcast mineral N fertiliser dressing at a rate of 70 kg N ha −1 (as ammonium sulphate nitrate) was applied at the six-leaf stage in all treatments.
Maize (cv. Atrium FAO) was sown at 5 cm depth in early May with a 75-cm row spacing and 13.3 cm between plants within rows. Herbicides were applied on all plots. Field operations are listed in Table 5 .

Sampling and analytical methods
At the five-leaf stage (V5), 40 of the youngest fully developed leaves were sampled manually in each harvest plot. The maize plants were whole-crop harvested at silage maturity leaving 15 cm stubble. The DM content was determined on a subsample of approximately 1 kg of the chopped fresh material. Plant material was oven-dried at 60 ˚C to constant weight (min 48 h).
Leaf P concentration was determined by digesting 1.5 g dried plant material in concentrated hydrochloric acid after ashing at 500 ˚C. The P concentration in the digest was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES, Yara, Analytical Services, Pocklington, UK). Leaf N concentration was determined by Kjeldahl digestion.
Phosphorus concentration of the whole crop was determined by digestion under pressure in a microwave oven following measurement by ICP-OES (EurofinsAgroTesting, Denmark).

Statistical analyses
Data from the two sites was analyzed in the R-Project software package version 3.4.1 using linear mixed-effects models from the R-package lme4 with treatments as a fixed effect and replicate as a random effect. The assumption of homogeneity of variance and normality of residuals was visually verified by plot of residuals against fitted values and histogram of the residuals. In cases where the treatment effect was found to be significant in a one-way analysis of variance, the differences between treatments for each location were analyzed by the Tukey ś honestly significant difference (HSD) using estimated marginal means from the R-package emmeans .
Significance was declared at the P ≤ 0.05 level of probability.