Especially during early developmental stages, competition with weeds can reduce crop growth and have a serious effect on productivity. Here, the effects of interactions between soil water content (SWC), nutrient availability, and competition from weeds on early stage crop growth were investigated, to better understand this problem. Field experiments were conducted in 2013 and 2014 using long-term study plots on loam soil in Hungary. Plots of maize (Zea mays L.) and a weed-maize combination were exposed to five fertilization treatments. SWC was observed along the 0-80 cm depth soil profile and harvested aboveground biomass (HAB) was measured. Significant differences were found between SWC in maize and maize-weed plots. In all treatments, measured SWC was most variable in soil depths of up to 50 cm, and at the 8-10 leaves (BBCH19) growth stage of the crop. The greatest depletion of SWC was detected within PK treatments across the entire soil profile and under both vegetation types, with depletion also considerable under NPK and NP treatments. Biomass growth was significantly influenced by weeds in treated plots between the BBCH 13 and 19 phenological stages, but water availability did not hamper growth rates in non-fertilized conditions. These findings suggest that, at early stages of crop growth, SWC model simulations need to include better characterisation of depth- and structure-dependent soil water uptake by vegetation.
Goldspur apple (Malus pumila cv. Goldspur) is one of the main fruit trees planted in semiarid loess hilly areas. The photosynthetic efficiency in leaves of eight-year-old trees were studied under different soil water conditions with a Li-6400 portable photosynthesis system and a Li-Cor1600 portable steady state porometer in order to explore the effects of soil water stress on photosynthesis and the suitable soil water content (SWC) for water-saving irrigation of apple orchards. The results showed that the leaf net photosynthetic rate (P N), transpiration rate (E), water-use efficiency (WUE), stomatal conductance (gs), intercellular CO2 concentration (Ci), and stomatal limiting value (Ls) displayed different threshold responses to soil water variation. When SWC was within a range of about 60%-86% of field capacity (FC), PN and E were maintained in a relative steady state. At an elevated level but below 60% of FC, both PN and E decreased evidently with decreasing soil moisture. The SWC needed to support WUE in a relatively steady state and at a high level was in the range of about 50%-71% of FC. When SWC was less than 48% of FC, g s and Ls declined with decreasing soil moisture, while Ci increased rapidly. Based on the analysis of the stomatal limitation of photosynthesis using two criteria (Ci and Ls) suggested by Farquhar and Sharkey, it was implied that the predominant cause of restricting PN had changed from stomatal limitation to nonstomatal one under severe water stress. In terms of water-saving irrigation for enhancing water-use efficiency, it was concluded that in semiarid loess hilly areas, the suitable range of SWC for water-saving irrigation in goldspur apple orchards is in the range of about 50%-71% of FC, and the most severe degree of soil water stress tolerated for photosynthesis is about 48% of FC. and S. Y. Zhang ... [et al.].
In order to use rationally switchgrass (Panicum virgatum L.) introduced in a large scale in semiarid regions on the Loess Plateau of China, we investigated and compared soil water storage dynamics, diurnal and seasonal changes in leaf photosynthetic characteristics, and biomass production of switchgrass grown under three different row spacing (20, 40, and 60 cm). Results indicated that photosynthetic parameters showed a pronounced seasonality. Diurnal course of net photosynthetic rate (P N) was bimodal, showing obvious midday depression, which was mainly due to stomatal limitation in May and June, by nonstomatal limitation in August, and both stomatal and nonstomatal factors in September. Generally, P N, stomatal conductance, instantaneous water-use efficiency, light-saturated net photosynthetic rate, saturation irradiance, and compensation irradiance increased with increasing row spacing. Plant height, leaf width, and a relative growth rate of biomass accumulation were significantly higher at the row spacing of 60 cm, while 20 cm spacing showed significantly higher aboveground biomass production and the biomass water-use efficiency. All these confirmed that soil water is the key limiting factor influencing switchgrass photosynthesis, and suggested that the wide row plantation (i.e., 60 cm) was more beneficial to switchgrass growth, while narrow spacing was in favor of improving switchgrass productivity and water-use efficiency., Z. J. Gao, B. C. Xu, J. Wang, L. J. Huo, S. Li., and Obsahuje seznam literatury
Hillslope hydrology in agricultural landscapes is complex due to a variety of hydropedological processes and field management possibilities. The aim was to test if there are any differences in soil properties and water regime along the hillslope and to compare vineyard rows (vine) with inter-rows (grass) area for those properties. The study determined that there are significant differences in the contents of soil particle fractions, pH, and humus content along the slope (P < 0.0001), with lower confidence level in bulk density (P < 0.05). Differences between row and inter-row space were significant for the pH, humus, and silt content, but for sand and clay content, and bulk density differences were not determined. The study determined differences in soil water content among five slope positions (P < 0.0001), and between row and inter-row vineyard space (all with P < 0.05). Where in the upper slope positions (e. g., P1) soil water content was higher than on lower slope positions. Higher soil water content was observed at higher slope positions, associated with clay content. However, it can be concluded that the retention of moisture on the slope is more influenced by local-scale soil properties (primarily soil texture) and variability of the crop (row/inter-row) than the position on the slope.
The response of gas exchange and chlorophyll fluorescence along with changes in simulated rainfall were studied in water stressed plants Hedysarum fruticosum var. mongolicum (H.f.m.). Net photosynthetic rate (PN), stomatal conductance (gs), leaf water potential (Ψleaf), and apparent carboxylation efficiency (PN/Ci) were significantly increased with the increase of rainfall. However, they did not change synchronously. The complete recovery of both PN and PN/Ci appeared 3 d after watering while gs and Ψleaf were recovered 1 d after treatment. Gas exchange characters increased sharply from 5 to 15 mm rainfall and then maintained steady state with increasing rainfall. During the initial phase of water recovery, photosystem 2 (PS2) activity was not affected and its complete recovery occurred also 3 d after rainfall. Hence the recovery of PN was attributed to both opening of stomata and increase in carboxylation efficiency. Furthermore, PS2 activity was really impaired by water stress and could recover to the normal status when the water stress disappeared. and S. L. Niu ... [et al.].
Advances in soil water content (SWC) monitoring technology continue to provide new and significant benefits to agriculture. An innovative approach for observing SWC is introduced using a portable rover platform traveling through in-ground horizontal access tubes and monitors the SWC in real time. A series of tests for evaluating the prototype portable rover were designed and conducted. It demonstrated very good mobility and produced records of the SWC in different horizons. The recorded values were then plotted as three dimensional (3D) patterns with high accuracy. The results show potential applications for this sensing approach, yielding horizontal monitoring of soil water in the root zone or deeper subsurface. and Pokročilé metody monitorování obsahu vody v půdě (SWC - soil water content) přinášejí nové a významné informace pro zemědělství. Inovativní zařízení k pozorování SWC bylo vyvinuto s použitím robota se snímačem půdní vlhkosti, který prochází zemními horizontálními přístupovými trubkami a monitoruje SWC v reálném čase. Byla provedena řada zkoušek pro otestování prototypu přenosného zařízení, které prokázalo velmi dobrou mobilitu a vytvořilo záznamy SWC v různých horizontech. Zaznamenané hodnoty byly potom vykresleny jako trojrozměrné (3D) grafy s vysokou přesností. Výsledky ověřily široké možnosti použití tohoto měřicího zařízení, které umožňuje horizontální i vertikální monitorování půdní vody v kořenové zóně rostlin nebo i v hlubším podloží.
In order to test the effects of irrigation depth on winter wheat photosynthesis, four treatments were applied in a field experiment using PVC growth tubes (identical amounts of water were applied on the land surface, and at 60, 75, and 90% of the depth for the winter wheat root distribution, denoted as D0, D60, D75, and D90, respectively). Compared to the surface irrigation treatment D0, the leaf area index, chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO2 concentration increased with irrigation depths. The values of these indicators obtained by the underground irrigation treatment D75 were higher than those of D60 and D90, and thus D75 was found to be the optimum irrigation depth. Furthermore, a positive but not significant correlation (r = 0.62) between carbon isotope discrimination (Δ13C) and grain yield was found. This study improves our understanding of the mechanism of underground water distribution control with depth, and the efficiency of
water-saving irrigation for winter wheat., L. J. Zheng, J. J. Ma, X. H. Sun, X. H. Guo, J. Jiang, R. Ren, X. L. Zhang., and Obsahuje bibliografii
CO2 exchange components of a temperate semi-desert sand grassland ecosystem in Hungary were measured 21 times in 2000-2001 using a closed IRGA system. Stand CO2 uptake and release, soil respiration rate (Rs), and micrometeorological values were determined with two types of closed system chambers to investigate the daily courses of gas exchange. The maximum CO2 uptake and release were -3.240 and 1.903 μmol m-2 s-1, respectively, indicating a relatively low carbon sequestration potential. The maximum and the minimum Rs were 1.470 and 0.226 μmol(CO2) m-2 s-1, respectively. Water shortage was probably more effective in decreasing photosynthetic rates than Rs, indicating water supply as the primary driving variable for the sink-source relations in this ecosystem type. and J. Balogh ... [et al.].
Soil volume changes of heavy soils due to soil water content change are followed by their volume changes in the process of its shrinkage and swelling. Values of soil volume changes depend on the type and on the content of clay minerals and on soil water content as well. Content of clay minerals is usually stable at the site, but soil water content is changing, depending on meteorological and hydrological conditions. Soil volume changes are performing in both - horizontal and vertical directions. Horizontal deformation of soil creates soil cracks and changes of their dimensions, vertical deformations lead to soil surface level changes. At a given time soil water content W depends on the thickness of the vadose zone layer Δz of soil, i.e. ?W = F (Δz). The article presents results of integral soil water content calculation based on the above mentioned relationship. Vertical changes of soil surface level were measured in the field, near the site Senné (East Slovakia Lowland). and Zmeny objemu ťažkých pôd spôsobené zmenou vlhkosti sú výsledkom ich objemových zmien v procese zmrašťovania a napučiavania. Veľkosť týchto zmien závisí od obsahu a druhu ílových minerálov v štruktúre pevnej fázy a od jej vlhkosti. Oproti vlhkosti meniacej sa v závislosti od klimatických a hydrologických podmienok je obsah ílových minerálov na danej lokalite stabilný. Objemové zmeny sa realizujú v horizontálnom i vertikálnom smere. Horizontálne objemové zmeny pôdy vytvárajú pukliny a menia ich dimenzie, vertikálne zmeny vyvolávajú zmeny polohy povrchu pôdy. V danom čase obsah vody v pôde W závisí na mocnosti zóny aerácie ťažkej pôdy Δz, t.j. platí vzťah W = F(Δz). Predkladaná štúdia uvádza výsledky kvantifikácie integrálneho obsahu vody v zóne aerácie ťažkej pôdy danej mocnosti zo zmien polohy jej povrchu, a to priamym meraním pre podmienky ťažkej pôdy na lokality Senné (Východoslovenská nížina).
In the field, the blister beetle Mylabris phalerata Pallas (Coleoptera: Meloidae) undergoes larval diapause in the ground, which lasts for nearly six months. The effect of the soil environment on this diapause was examined. Final instar larvae kept at temperatures of >= 26°C do not enter diapause and continued to develop regardless of the soil water content and photoperiod. Below 25°C the final instar larvae entered diapause regardless of soil water content and photoperiod. The early stages, particularly L2, appeared to be more important for diapause induction than the later stages. However, the other instars were also sensitive. Temperature, rather then photoperiod was the main factor influencing pupal duration.