A loss function to evaluate agricultural decision-making under uncertainty: a case study of soil spectroscopy

Modern sensor technologies can provide detailed information about soil variation which allows for more precise application of fertiliser to minimise environmental harm imposed by agriculture. However, growers should lose neither income nor yield from associated uncertainties of predicted nutrient concentrations and thus one must acknowledge and account for uncertainties. A framework is presented that accounts for the uncertainty and determines the cost–benefit of data on available phosphorus (P) and potassium (K) in the soil determined from sensors. For four fields, the uncertainty associated with variation in soil P and K predicted from sensors was determined. Using published fertiliser dose–yield response curves for a horticultural crop the effect of estimation errors from sensor data on expected financial losses was quantified. The expected losses from optimal precise application were compared with the losses expected from uniform fertiliser application (equivalent to little or no knowledge on soil variation). The asymmetry of the loss function meant that underestimation of P and K generally led to greater losses than the losses from overestimation. This study shows that substantial financial gains can be obtained from sensor-based precise application of P and K fertiliser, with savings of up to £121 ha^?1 for P and up to £81 ha^?1 for K, with concurrent environmental benefits due to a reduction of 4–17 kg ha^?1 applied P fertiliser when compared with uniform application.

     

Exploring the variation in soil saturated hydraulic conductivity under a tropical rainforest using the wavelet transform

Saturated hydraulic conductivity (K_s) of the soil is a key variable in the water cycle. For the humid tropics, information about spatial scales of K_s and their relation to soil types deduced from soil map units is of interest, as soil maps are often the only available data source for modelling. We examined the influence of soil map units on the mean and variation in K_s along a transect in a tropical rainforest using undisturbed soil cores at 0–6 and 6–12 cm depth. The K_s means were estimated with a linear mixed model fitted by residual maximum likelihood (REML), and the spatial variation in K_s was investigated with the maximum overlap discrete wavelet packet transform (MODWPT). The mean values of K_s did not differ between soil map units. The best wavelet packet basis for K_s at 0–6 cm showed stationarity at high frequencies, suggesting uniform small‐scale influences such as bioturbation. There were substantial contributions to wavelet packet variance over the range of spatial frequencies and a pronounced low frequency peak corresponding approximately to the scale of soil map units. However, in the relevant frequency intervals no significant changes in wavelet packet variance were detected. We conclude that near‐surface K_s is not dominated by static, soil‐inherent properties for the examined range of soils. Several indicators from the wavelet packet analysis hint at the more dominant dynamic influence of biotic processes, which should be kept in mind when modelling soil hydraulic properties on the basis of soil maps.     

Detection of Citrus psorosis virus in field trees by direct tissue blot immunoassay in comparison with ELISA, symptomatology, biological indexing and cross-protection tests

Serological detection of Citrus psorosis virus (CPsV) by direct tissue blot immunoassay (DTBIA) and by double (DAS) and triple (TAS) antibody sandwich ELISA, was compared in samples from various citrus varieties growing in the glasshouse and in the field. In young shoots and leaves, CPsV was readily detected by the three procedures, whereas DTBIA detection in old leaves was less consistent. DTBIA detection and ELISA readings in nine different citrus varieties were similar, suggesting that CPsV accumulates to equivalent levels in all of them. In infected field trees from Spain or Italy, CPsV was consistently detected by TAS ELISA, even in samples of old leaves in winter, whereas DTBIA detection in the same trees was reliable only when using young shoots. Detection of CPsV by DTBIA and by DAS and TAS ELISA in previously untested field trees correlated perfectly with psorosis diagnostics based on biological indexing, specifically with the capacity of those sources to cross-protect against challenge inoculation with psorosis B. Some trees without bark scaling were shown to be psorosis-infected by biological indexing and to contain CPsV by serological tests; other trees showing psorosis-like bark or leaf symptoms in the field were shown to be psorosis-free by biological indexing and also CPsV-free by serology. This is the first time that the presence of CPsV has been correlated with psorosis infection as diagnosed by biological indexing.     

Effects of maternal nutrition and stage of gestation on body weight, visceral organ mass, and indices of jejunal cellularity, proliferation, and vascularity in pregnant ewe lambs

Peripubertal ewe lambs (44.3 +/- 1.1 kg of initial BW) were used in a 2 x 3 factorial design to test the effects of plane of nutrition (diet) and stage of gestation on maternal visceral tissue mass, intestinal cellularity, crypt cell proliferation, and jejunal mucosal vascularity. Singleton pregnancies to a single sire were established by embryo transfer, and thereafter ewes were offered a control (Control) or high (High) amount of a complete diet (2.84 Mcal/kg and 15.9% CP; DM basis) to promote slow or rapid maternal growth rates. After d 90 of gestation, feed intake of the Control group was adjusted weekly to maintain BCS and meet the increasing nutrient demands of the gravid uterus. Ewes were slaughtered at 50 d (n = 6 Control; n = 5 High), 90 d (n = 8 Control; n = 6 High), or 130 d (n = 8 Control; n = 6 High) of gestation. Ewes were eviscerated and masses of individual organs were recorded. The jejunum was sampled and processed for subsequent analyses. Final ewe BW for Control-fed ewes was similar at d 50 and 90 and increased (P = 0.10) from d 90 to 130 (46.0, 48.9, and 58.2 +/- 1.6 kg, respectively), whereas final BW increased (P 相似文献   

Purification and serology of virions of impatiens necrotic spot tospovirus

Impatiens necrotic spot tospovirus (INSV) virions were purified using a procedure devised for tomato spotted wilt tospovirus (TSWV) from systemically infectedNicotiana benthamiana plants grown at 33 °C day/26 °C night and a photoperiod of 14 hours. With plants grown at 24/18 ° C purification was unsuccessful. In SDS-PAGE the protein pattern of INSV was similar to that reported for TSWV, except the appearance of a single G2 protein band. A polyclonal antiserum, prepared against virions, reacted in Western blots with INSV nucleoprotein and glycoproteins but only with TSWV glycoproteins. In DAS ELISA the antiserum reacted with both INSV and TSWV infected plant sap and, after absorption with TSWV, only with INSV. In TAS ELISA the antiserum trapped both INSV and TSWV nucleoproteins and glycoproteins as detected by specific monoclonal antibodies, and, after absorption with TSWV, only the homologous proteins. This appears to be the first report of the purification of INSV virions and the production of an antiserum reacting with both nucleoprotein and glycoprotein antigens.