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Nitrogen fertilizer is applied to supplement soil nitrogen supply to maximize forage brassica crop dry-matter production. However, nitrogen fertilizer applications in excess of that required to maximize growth result in potentially toxic nitrate-nitrogen ( NO3-N) concentrations in grazeable plant tissues. Three experiments, two for forage kale at Lincoln ( Canterbury) and one for forage rape at Hastings ( Hawke's Bay) in New Zealand were grown under different rates of nitrogen (0-500 kg N ha−1) to determine the effect of different rates of nitrogen on NO3-N content of different plant parts of the crops. One of the kale experiments was grown with either full irrigation or no rain and no irrigation over summer, hereafter referred to as summer drought. The NO3-N concentration on a whole plant (weighted average) basis increased from 0·1 mg g−1 dry matter for the control plots to 2·30 mg g−1 for the 500 kg N ha−1 plots for forage kale. It increased from 0·99 for the control plots to 3·37 mg g−1 for the 200 kg N ha−1 plots for forage rape crops. However, NO3-N concentration increased with N supply under the summer-drought plots from an average of 0·33 mg g−1 when ≤120 kg N ha−1 was applied to 2·30 mg g−1 for the 240 kg N ha−1 treatments but was unaffected by N supply under irrigation. The NO3-N concentrations were higher in the stems and the petiole (which included the midrib of the leaf) than leaves in all three experiments. The NO3-N concentration was highest at the bottom of the kale stem and decreased towards the top. We recommend N application rates based on soil tests results, and for conditions similar to the current studies up to 300 kg N ha−1 under irrigation and adjusted lower N rates for regions prone to dry summers. [ABSTRACT FROM AUTHOR]

Establishing the radiation-use efficiency ( RUE) of forage brassica crops will aid our understanding of their photosynthetic performance. The concept of RUE has been developed for cereals and legumes, but there is limited information for forage brassica crops. Three experiments defining the influence of different sowing dates on 'Gruner' kale ( Brassica oleracea acephala L.) dry matter production were conducted at Hastings (Hawkes Bay) and Lincoln (Canterbury) in New Zealand between 2002 and 2009. These trials were also evaluated for radiation interception and RUE. Delayed sowing increased RUE in two out of three experiments across sites: from 1·93 g MJ−1 photosynthetically active radiation ( PAR) for December-sown crops to 2·72 g MJ−1 PAR ( P < 0·001) for January-sown crops at Hastings and from 1·50 for September-sown crops to 2·00 g MJ−1 PAR ( P < 0·001) for November-sown crops at Lincoln. The different sowing dates and years of experimentation provided a range of mean temperatures (from 13 to 16°C) during the vegetative period. Across years and sowing dates, RUE was strongly correlated with mean temperature (R2 = 0·81) and sowing date (R2 = 0·64), but weakly correlated with season length (R2 = 0·11) and dry matter (R2 = 0·002). There was also a strong correlation (R2 = 0·83) between sowing date and mean temperature. The increase in RUE with delayed sowing was therefore mainly attributed to increased mean temperatures. Radiation-use efficiency increased at about 0·41 g MJ−1 for each 1°C increase from 13 to 16°C. [ABSTRACT FROM AUTHOR]

Chelifers (Arachnida: Pseudoscorpionida), also known as pseudoscorpions, have been reported to be beneficial honeybee hive generalist pest predators for over 100 years and are occasionally noted by beekeepers in their hives. We collected chelifers within or closely associated with beehives in New Zealand. Under video observation conditions, they predated upon varroa mites while studiously ignoring bee larvae. Varroa mites reproduce at exponential rates during the spring season, and current chemical miticides rely on single treatments aiming for at least 90% control. An alternate strategy, removal of mites at a rate matching their reproductive capacity, although mathematically obvious, fails unless a suitable biological control agent is available. Our observations build on over 100 years of sporadic work to provide further evidence that chelifers show clear potential to be a suitable predator for varroa management in beehives. Approximately 25 chelifers can be expected to manage varroa populations in a single hive. [ABSTRACT FROM AUTHOR]

The extent to which SOM content and texture affect C and N dynamics during dry/wet cycles is poorly understood. A laboratory incubation study was conducted to quantify short-term changes in SOM (C & N) fractions and their relationship to C and N mineralisation in response to dry/wet cycles along a SOM gradient in two soil types of differing texture. The experiment consisted of three phases: pre-incubation, treatment and recovery. Three soil water content (SWC) treatments were established: continuously wet (WW; field capacity (FC)), moderately dry (MD; 120% of SWC at wilting point (WP)) and very dry (VD; 80% of SWC at WP). Each of the two 'dry' treatments were either maintained continuously dry (MD & VD) or subjected to three sequential 20 d-long dry/wet cycles (MDW & VDW) during the experiments treatment phase. All soils were returned to FC at the start of the recovery phase and analyses were carried out at the end of each phase. Over all, the results of this study showed that SOC content and texture are important factors affecting the size of several commonly measured fractions of soil organic matter, but the stability and resilience of these fractions depended on the duration and amplitude of dry/wet cycles. Whereas most of the measured C and N fractions (cold water extractable C [CWEC] and hot water extractable C [HWEC], microbial biomass C [MBC] and N [MBN], inorganic N) were affected by both the duration (e.g. MDW vs. MD) and amplitude (e.g. MDW vs. VDW) of dry/wet cycles, the response differed between fractions and the effects tended to be much stronger in silt loam than in clay loam soils. The duration and amplitude of dry/wet cycles also suppressed the rate of both C and N mineralisation in both soils compared to continuously wet conditions. There was also strong evidence that the C mineralised from both soils during the recovery phase (i.e. following rewetting of dry soils) compensated for the reduction in C mineralised during the treatment phase. For N mineralisation, the amplitude of dry/wet cycles was at least as important as the duration of the cycles in affecting N mineralisation during the recovery phase. Much higher rates of N mineralisation were observed in soils that had previously been exposed to very dry conditions, particularly in the silt loam soil. There was some evidence that HWEC was the primary source of the C made available during the rewetting of dry soil and that it contributed to the increased availability of CWEC and supported an increase in MBC and C mineralisation in both soils during the recovery phase. In contrast, there was no evidence that differences in availability of C and N fractions affected the rate of N mineralisation following the return of dry soils to continuously wet conditions. Further research is need to resolve the primary factors that regulate N mineralisation response to the recovery from dry soil conditions. [ABSTRACT FROM AUTHOR]

Prostaglandins are involved in multiple processes important for fertility, with previous work in mice highlighting a potential role for the HSD17B12 gene in prostaglandin biosynthesis. This study aimed to determine the associations among circulating prostaglandin concentrations, a missense SNP in the HSD17B12 gene predicted to disrupt protein function, and fertility traits in first-lactation Holstein-Friesian dairy cows. We used a study population of approximately 500 animals specifically bred to have either a positive (POS, +5%) or negative (NEG, -5%) genetic merit for fertility (FertBV). Genotypes of a previously identified SNP (rs109711583) in HSD17B12 were determined, with 116 animals genotyped as AA, 215 genotyped as AG, and 153 genotyped as GG. Plasma concentrations of prostaglandin E 2 and the PGF 2α metabolite PGFM were determined at 3 time points (12 mo of age, 4 d postpartum, and 5 wk postpartum during first lactation) in a selection of animals with AA and GG genotypes from both the POS and NEG FertBV groups (n = 33-40 in each genotype for each FertBV group). Binary reproductive traits (yes or no) examined included submission for artificial breeding in the first 3 or 6 wk of the seasonal breeding period; conception to first service; conception during the first 6 wk of the breeding period; and pregnant at the end of the breeding period. Uterine health at 6 wk after calving was examined by evaluating the percentage of polymorphonuclear leukocytes following uterine cytology and by scoring vaginal discharge based on the presence of purulent material. The 3-wk submission rate was increased in animals that carried the G allele of the missense SNP in HSD17B12, but no differences were present among genotypes for 6-wk submission rate. The trait was additive, with each increase of the G allele increasing the 3-wk submission rate by 6 to 7%. We did not observe any consistent associations between SNP alleles and circulating PGE 2 concentrations; however, a complex 3-way interaction among time, fertility group, and SNP allele was present for PGFM concentrations. Plasma concentrations of PGE 2 were increased approximately 40% at 5 wk postpartum in animals that were submitted for breeding within 3 or 6 wk of the start of the breeding season, and in those that conceived during the first 6 wk of breeding, compared with those that did not. Plasma concentrations of PGFM were decreased approximately 20% in those animals that conceived to their first service and tended to be decreased in animals that were pregnant at the end of the breeding period, compared with those that were not. In summary, associations were observed between the SNP in HSD17B12 and submission rate by d 21 of the breeding season, as well as between circulating prostaglandin concentrations and fertility traits, but the SNP was not consistently linked to changes in prostaglandin concentrations. Thus, the association between submission rate by d 21 of the breeding season and the SNP in HSD17B12 were unlikely driven by changes in prostaglandins., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Accuracy of determining radiation interception, and hence radiation use efficiency, depends on the method of measuring photosynthetically active radiation intercepted. Methods vary, from expensive instruments such as Sunfleck ceptometers to simple methods such as digital photography. However, before universal use of digital photography there is need to determine its reliability and compare it with conventional, but expensive, methods. In a series of experiments at Lincoln, New Zealand, canopy development for barley, wheat, white clover and four forage brassica species was determined using both digital photographs and Sunfleck ceptometer. Values obtained were used to calculate conversion coefficient (Kf/Ki) ratios between the two methods. Digital photographs were taken at 45° and 90° for barley, wheat and white clover and at only 90° for brassicas. There was an interaction of effects of crop and cultivar for the cereal crops. Barley closed canopies earlier than wheat, and 'Emir' barley and 'Stettler' wheat had consistently higher canopy cover than 'Golden Promise' and 'HY459', respectively. Canopy cover was consistently larger at 45° than 90° for cereals. However, for white clover, the angle of digital photography was not important. There was also an interaction between effects of species and method of determining canopy cover for brassicas. Photographs gave higher cover values than ceptometer for forage rape and turnip, but the relationship was variable for forage kale and swede. Kf/Ki ratios of 1.0-1.10 for cereals, white clover and forage rape and turnip show that digital photographs can be used to estimated radiation interception, in place of Sunfleck ceptometer, for these crops., (© 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.)