Greater Leaf Area Index Research Articles

Partitioning urban forest evapotranspiration based on integrating eddy covariance of water vapor and carbon dioxide fluxes

Partitioning of evapotranspiration (ET) in urban forest lands plays a vital role in mitigating ambient temperature and evaluating the effects of urbanization on the urban hydrological cycle. While ET partitioning has been extensively studied in diverse natural ecosystems, there remains a significant paucity of research on urban ecosystems. The flux variance similarity (FVS) theory is used to partition urban forest ET into soil evaporation (E) and vegetation transpiration (T). This involves measurements from eddy covariance of water vapor and carbon dioxide fluxes, along with an estimated leaf-level water use efficiency (WUE) algorithm. The study compares five WUE algorithms in partitioning the average transpiration fraction (T/ET) and validates the results using two years of oxygen isotope observations. Although all five FVS-based WUE algorithms effectively capture the dynamic changes in hourly scale T and E across the four seasons, the algorithm that assumes a constant ratio of intercellular CO2 concentration (ci) to ambient CO2 concentration (ca) provides the most accurate simulation results for the ratio of T/ET. The performance metrics for this specific algorithm include the RMSE of 0.06, R2 of 0.88, the bias of 0.02, and MAPE of 8.9 %, respectively. Comparing urban forests to natural forests, the T/ET in urban areas is approximately 2.4–25.3 % higher, possibly due to the elevated air temperature (Ta), greater leaf area index (LAI), and increased soil water availability. Correlation analysis reveals that the T/ET dynamic is primarily controlled by Ta, LAI, net radiation, ca, and soil water content at half-hourly, daily, and monthly scales. This research provides valuable insights into the performance and applicability of various WUE algorithms in urban forests, contributing significantly to understanding the impact of urbanization on energy, water, and carbon cycles within ecosystems.

Ridge-Furrow Mulching Enhances Capture and Utilization of Rainfall for Improved Maize Production under Rain-Fed Conditions

The capture and utilization of rainwater by crops under various mulching conditions have great importance in agriculture production systems, especially in dry-prone regions. Understanding the effect of mulching on rainwater use efficiency growth and yield of a crop is very important. For this purpose, field experiments were conducted in 2017 and 2018 to evaluate the potential of ridge-furrow mulching on maize growth and development under rain-fed conditions. The field study compared four treatments, i.e., ridge-furrow without mulch (WM), black plastic mulch (BM), transparent plastic mulch (TM) and grass mulch (GM). The BM treatment consistently increased the soil moisture and temperature, resulting in earlier emergence, as well as increased plant height and plant biomass, compared to the WM treatment. Compared to WM, the two-years mean yield of maize with BM, TM and GM were recorded to be increased by 33.6%, 28.1% and 10.8%, respectively. The BM produced a maximal crop growth rate at 90 days after sowing (DAS) as specified by a greater leaf area index. Transpiration rate and leaf stomatal conductance were significantly higher with BM and TM than with WM, however, the BM treatment showed the highest net photosynthetic rate in both years. Net income for the BM treatment was the highest (USD 1226 ha−1) of all the treatments and USD 335 ha−1 greater than WM. As growth, yield and net income of maize were improved with BM, therefore this treatment was found to be the most effective for maize production in rain-fed conditions. This system is evaluated at a small scale, hence to maximize its effectiveness on a large scale, a simulation design needs to be developed.

Precipitation effects on grassland plant performance are lessened by hay harvest

Climate and human management, such as hay harvest, shape grasslands. With both disturbances co-occurring, understanding how these ecosystems respond to these combined drivers may aid in projecting future changes in grasslands. We used an experimental precipitation gradient combined with mimicked acute hay harvest (clipping once a year) to examine (1) whether hay harvest influences precipitation effects on plant performance (cover and height) and (2) the role of inter-specific responses in influencing plant performance. We found that hay harvest reduced the strength of precipitation effects on plant performance through changes in bare-ground soil cover. Species performance were mainly influenced by change in abiotic factors, often responding negatively, as hay harvest increased bare-ground amount. Conversely, altered precipitation without hay harvest promoted plant species performance through abiotic factors change first, followed by biotic. Most species, including the dominant grass Schizachyrium scoparium, increased their performance with greater leaf area index (proxy for canopy structure). Our experiment demonstrates that plant performance responds directly to abiotic factors with hay harvest, but indirectly without hay harvest. Positive effects of increasing precipitation were likely due to microhabitat amelioration and resource acquisition, thus inclusion of hay harvest as a disturbance lessens positive impacts of biotic variables on species performance to climate change.

The exclosure cage technique revisited: Pasture responses under continuous stocking and their relationship with estimates of forage accumulation in grazing experiments

AbstractForage accumulation (FA) is a key response in grazing experiments, and estimates of FA in continuously stocked pastures are often obtained using exclosure cages. This study evaluated how 14‐, 21‐, and 28‐d exclusion periods using cages affected morphological, physiological, and morphogenetic responses of continuously stocked ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) pastures maintained at 20‐ and 30‐cm canopy height and how this affected estimates of FA. Grazing exclusion resulted in greater rates of leaf elongation (LER; 1.62 vs. 1.37 cm tiller−1 d−1), stem elongation (SER; 0.16 vs. 0.07 cm tiller−1 d−1), leaf growth (101 vs. 86 kg dry matter [DM] ha−1 d−1), and stem growth (3.4 vs. 1.8 kg DM ha−1 d−1) inside the cages compared with outside. Greater LER resulted in greater final leaf length and leaf area index (LAI) in longer exclusion periods. With greater LAI, photosynthesis was greater within the exclosure cages than on pasture (54.5 vs. 43.9 μmol CO2 m−2 s−1). Greater leaf growth rate, together with same tiller population density and leaf senescence rate (LSR) across exclusion periods, resulted in overestimated FA by 14, 26, and 24% for 14‐, 21‐, and 28‐d exclusions, respectively. There was no effect of canopy height on FA, because greater LER and SER values in 30‐cm canopies were compensated by greater LSR. Choice of sites for cage placement by visual appraisal and reduced number of sampling sites resulted on “negative” values of calculated FA for the 14‐d exclusion, making the choice of sampling sites a major source of error in estimation of actual FA. Increasing the number of sampling sites and using indirect measurements of forage mass (FM) may increase the accuracy of FM and FA estimates.

Plant growth habit and nitrogen fertilizer effects on rhizoma peanut biomass partitioning during establishment

AbstractRhizoma peanut (RP; Arachis glabrata Benth.) is an important perennial forage legume in the US Gulf Coast region, but propagation using rhizomes and prolonged establishment periods limit its adoption. Genotypes and management practices that hasten establishment are needed. Our objective was to determine the effects of RP growth habit and nitrogen (N) fertilizer application during shoot emergence on biomass partitioning and measures of establishment success during the year‐of‐ and year‐after‐planting. Field experiments were conducted during 2016 through 2018. Treatments were the factorial combinations of two RP entries differing in growth habit (decumbent germplasm Ecoturf and upright cultivar ‘UF Tito’) and three N rates (0, 40, and 80 kg/ha applied 10 weeks after planting [WAP]) arranged in four replications of a randomized complete block design. Upright UF Tito had greater shoot (194 vs. 125 g/m2) and root‐rhizome biomass (249 vs. 111 g/m2) than decumbent Ecoturf at the end of the year of planting. Early growth patterns explained this response in part, as UF Tito had greater leaf area index (LAI; 0.58 vs. 0.39) and lesser root‐rhizome: shoot ratio (0.62 vs. 0.77) than Ecoturf at 20 WAP. Nitrogen fertilization had minimal effects on shoot biomass, and it did not affect root‐rhizome biomass. The entry effect on establishment performance persisted through the year after planting with UF Tito outperforming Ecoturf. Use of an RP genotype that prioritized leaf area and shoot versus root‐rhizome biomass during early growth was more important than N fertilization in expediting RP establishment.

Performance of Five Rice (Oryza sativa L.) Varieties as Influenced by Crop Establishment under Irrigated Lowland Conditions

This study aimed to determine the growth and yield performance of five rice varieties under the different crop establishments and assess rice profitability as influenced by crop establishment under irrigated lowland conditions. The study was laid out in a split-plot arranged in an RCBD with three replications. Crop establishment was designated as the main plot while rice varieties as a subplot. Results revealed that the direct row seeding method significantly showed a significant advantage in agronomic and yield and yield component parameters over the transplanting method among rice varieties tested. Heirloom red rice significantly headed earlier (63.17 days) when planted in both crop establishments and obtained the tallest plant height, greater leaf area index, the heavier weight of 1,000 grains, and grain yield. There was a significant interaction effect on crop establishment and rice variety recorded from sowing to heading and maturity. Cost and return analysis revealed that the direct row seeding method achieved higher gross income (USD 2,012.00) and gross margin (USD 1,086.60) than the transplanting method. Heirloom red rice significantly achieved the highest grain yield (5.85 t ha-1), resulting in a higher gross income and gross margin of USD 2,340.00 and USD 1,352.45, respectively. Direct row seeding is applicable as an effective cost-reducing method of crop establishment for lowland rice production. Besides, it can shorten the time of crop establishment. Heirloom red rice with dual characteristics as an irrigated lowland and upland rice cultivar is feasible for direct row seeding and transplanting methods during the dry season.

Aerobic Rice with or without Strategic Irrigation in the Subtropics

Modern rice varieties adapted to aerobic (dryland) conditions have expanded to new rice growing systems thanks to their plasticity in adapting to rainfed and irrigated conditions. This is important because, as water becomes scarce in paddy rice regions (as it is already in Australia), there will be a move towards tropical to subtropical dryland rainfed rice with attendant problems of drought and low temperature. To assess rice adaptability in the wet season of the semi-arid subtropical conditions of coastal central Queensland, field experiments were established for a late season (in January) planting in 2014 and early season planting in November 2015 with 13 varieties developed by Australian Agriculture Technologies (AAT) Ltd were seeded in a vertisol soil. This was to assess their adaptation to rainfed conditions and their response to strategic irrigation. Water scarcity and low temperature prior to and at flowering were important factors constraining yield. Early flowering varieties in the late season planting escaped the otherwise cold and drought stress during the reproductive stage and had higher yields. In the second year, earlier planting made possible with strategic irrigation avoided the low temperature constraint on yield, but without follow-up strategic irrigation, yields were still low. The average yield of varieties increased from 1.5 times (AAT 4) to 16.3 times (AAT 15) with strategic irrigation compared with rainfed yields averaged across years. The increase in yield with strategic irrigation was associated with a greater leaf area index, spikelet fertility, and instantaneous water use efficiency during flowering. Strategic irrigation concentrated roots in the top 15 cm, but differences in yield between varieties under rainfed conditions were not related to root properties. It is important to consider variations in flowering time, yield potential, and drought patterns when developing rice varieties for rainfed semi-arid tropical conditions, as well as when quantifying the benefits of strategic irrigation.

Modelling non‐stationary water ages in a tropical rainforest: A preliminary spatially distributed assessment

AbstractPristine tropical forests play a critical role in regional and global climate systems. For a better understanding of the eco‐hydrology of tropical “evergreen” vegetation, it is essential to know the partitioning of water into transpiration and evaporation, runoff and associated water ages. For this purpose, we evaluated how topography and vegetation influence water flux and age dynamics at high temporal (hourly) and spatial (10 m) resolution using the Spatially Distributed Tracer‐Aided Rainfall‐Runoff model for the tropics (STARRtropics). The model was applied in a tropical rainforest catchment (3.2 km2) where data were collected biweekly to monthly and during intensive monitoring campaigns from January 2013 to July 2018. The STARRtropicsmodel was further developed, incorporating an isotope mass balance for evapotranspiration partitioning into transpiration and evaporation. Results exhibited a rapid streamflow response to rainfall inputs (water and isotopes) with limited mixing and a largely time‐invariant baseflow isotope composition. Simulated soil water storage showed a transient response to rainfall inputs with a seasonal component directly resembling the streamflow dynamics which was independently evaluated using soil water content measurements. High transpiration fluxes (max 7 mm/day) were linked to lower slope gradients, deeper soils and greater leaf area index. Overall water partitioning resulted in 65% of the actual evapotranspiration being driven by vegetation with high transpiration rates over the drier months compared to the wet season. Time scales of water age were highly variable, ranging from hours to a few years. Stream water ages were conceptualized as a mixture of younger soil water and slightly older, deeper soil water and shallow groundwater with a maximum age of roughly 2 years during drought conditions (722 days). The simulated soil water ages ranged from hours to 162 days and for shallow groundwater up to 1,200 days. Despite the model assumptions, experimental challenges and data limitation, this preliminary spatially distributed model study enhances knowledge about the water ages and overall young water dominance in a tropical rainforest with little influence of deeper and older groundwater.

Wheat straw mulch improves summer maize productivity and soil properties

Crop residue mulch in agricultural systems preserves soil health and improves crop productivity through its moderating influence on soil temperature regime and enhanced moisture retention. Therefore, a field experiment was conducted to determine the changes in soil properties and grain yield of irrigated summer maize in response to wheat straw mulching in the Northern maize region in China. The treatments investigated were: i) application of wheat straw mulch (5000 kg ha–1); and ii) no-mulch application (control). Maize growth and yield attributes were determined during various growth stages, and soil hydro-thermal properties were recorded for two depths (0-15 and 15-30 cm). Straw mulch increased the yield by 18% and also increased total dry biomass yield by 20%, compared to no-mulch. Yield increment was attributed to the increased number of ears per area and kernels number per ear. The effect on thousand kernels weight was found non-significant. Vigorous maize growth was observed under straw mulch treatment, having greater leaf area index, unit leaf rate, leaf area duration, and crop growth rate. Similarly, the dry matter partitioning for maize kernels was greater in mulch treatment. At the late reproductive stages (R3 and R5), SPAD values for ear and below-ear leaves were higher under mulch treatment. Straw mulch decreased the daytime soil temperature by 1.9 and 1.5°C on average for 0-15 and 15-30 cm soil layers, respectively. Whereas, the soil moisture content increased about 2.5% (0-15 cm) and 3% (15- 30 cm) under the mulch treatment. In crux, leftover crop residue application as mulch in irrigated maize could be a sustainable agronomic option to increase the crop productivity.
 Highlights - Wheat straw mulch improved maize grain yield by approx. 18% mainly by increased kernel numbers per ear. - Maize growth attributes and SPAD values were improved under mulch treatment compared to no-mulch. - Straw mulching helped in maintaining comparatively higher soil moisture content (~2 %) and reduced the soil temperature (~1.72°C) during the crop growth period.

Solar radiation-use characteristics of indica/japonica hybrid rice (Oryza sativa L.) in the late season in southeast China

New indica and japonica hybrid rice cultivars, such as the Yongyou series, provide farmers with very high yield potential. However, information on their canopy light capture and solar radiation use efficiency in the late season is limited. Field experiments were performed to compare the radiation-use parameters of four rice types: indica rice (IR), inbred japonica rice (IJR), hybrid japonica rice (HJR), and hybrid indica/japonica rice (HIJR), from 2016 to 2018 during the late season in Hangzhou, China. The grain yield, aboveground biomass, intercepted solar radiation (SI), and radiation-use efficiency (RUE) of the HIJR were on average respectively 13.4%–53.4%, 14.3%–30.6%, 7.6%–21.4%, and 8.2%–14.9% higher than those of the HJR, IJR, and IR. The leaf area index (LAI) of the HIJR was 18.2%–57.0% greater than that of the IJR and HJR at four growth stages, resulting in respectively 17.8%–38.5% and 10.7%–42.8% greater canopy light interception rates (LIR) and amount of intercepted solar radiation during the vegetative stage. The prolonged grain-filling stage also led to respectively 33.9%–52.6% and 30.5%–51.4% increases in amounts of incident and intercepted radiation for the HIJR relative to the IR during grain filling. These results indicate that the SI superiority of the HIJR was caused by canopy closure as rapid as that of the IR during the vegetative stage (greater LAI and canopy LIR during the growing season) and a grain-filling stage as long as that of the HJR. For grain-filling stage, differences in leaf Pn between HIJR, IR, and IJR were not significant, suggesting that the greater RUE of the HIJR (12.7%–52.8% higher) than that of the other rice types resulted from improved canopy architecture after flowering (FL). Principal components analysis (PCA) revealed that the superiority of the HIJR in terms of solar radiation use resulted from the greater canopy light capture capability of IR and the prolonged growth period (especially during grain filling) of japonica rice in the late growing season.

Optimizing efficacy of acetochlor + atrazine and dicamba at various doses to manage Conyza stricta L. in sugarcane

Abstract Background: Conyza stricta L. (Horse weed) is an annual problematic weed in an agricultural ecosystem and considerably decreases the crop yield and quality. Objective: To determine the most effective pre and post emergence herbicides and their dose to control C. stricta in sugarcane crop. Methods: A two years field study comprised of six herbicides treatments along with weedy check and hand weeding. The design of study was RCBD with three replications. Results: Hand weeding recorded more leaf area index (LAI), crop growth rate (CGR) and net assimilation rate (NAR), biological and stripped yield. However, greater LAI, CGR and NAR, biological and stripped yield were recorded by acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) and dicamba at the rate of 466 g ha-1 (post emergence). All the treatments produced statistically comparable harvest index except weedy check, which produced less harvest index. Minimum C. stricta density and dry weight were recorded for acetochlor + atrazine at the rate of 2,715 g ha-1 and dicamba at the rate of 466 g ha-1. Acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) and dicamba at the rate of 466 g ha-1 (post emergence) gave better C. stricta control with high herbicides efficiency index. Conclusion: Acetochlor + atrazine at the rate of 2,715 g ha-1 (pre emergence) or dicamba at the rate of 466 g ha-1 (post emergence) may be used for efficient control of C. stricta in sugarcane.

Conversion Efficiency of Photosynthetically Active Radiation for Soybean Cultivations in Spatial Arrangements

The objective of this paper was to assess the efficiency of photosynthetically active radiation (PAR) intercepted in dried phytomass of soybean cultivars of determinate and indeterminate growth habits in different spatial arrangements. All experiments were carried out during the 2013/2014 crop year, two soybean cultivars (BMX Ativa RR/determinate and BMX Turbo RR/indeterminate) in a spatial arrangements (45, crossed, 20, 20 × 40, 20 × 60, 20 × 80 cm). Starting from first emergence up to the point of maturation, 14 phytomass assessment were evaluated with seven days interval, in which one plant was sampled per repetition. Greater conversion efficiencies of solar radiation were obtained in paired arrangements. Paired arrangements, and 20 cm, lead to a greater leaf area index, and possibly a greater interception of the diffused radiation and an increase of conversion efficiency and the overall cultivation productivity of BMX Ativa RR and BMX Turbo RR.

Productive and Nutritional Aspects of Tithonia diversifolia Fertilized With Biofertilizer and Irrigated

Little is known about the agronomic aspects of Mexican Sunflower (Tithonia diversifolia), in spite of its potential for multiple uses. In this study, we evaluated the effects of application rates of biofertilizer and irrigation on yield, growth, and leaf chlorophyll and nutrient content of Mexican Sunflower. In an experiment in the Brazilian semi-arid region, we used a 5 × 2 factorial arrangement, consisting of five application rates of biofertilizer (0, 40, 80, 120, and 160 m3 ha-1), with and without irrigation. The statistical design was randomized blocks with three replications. Irrigated plants of Mexican Sunflower had greater dry and fresh matter yields, greater height, and greater leaf area index and leaf contents of K, Zn, and B. However, the high concentration of bicarbonate in the irrigation water reduced the leaf contents of N, Ca, S, Fe, and Mn. The mean increase in the two cuttings obtained with the use of irrigation was 350% and 314% for fresh and dry matter, respectively. The increase in the biofertilizer application increased the leaf chlorophyll contents of irrigated plants; however, it did not result in production or nutritional gains. In regions with low availability of rainfall, irrigated cultivation of Mexican Sunflower is recommended.

PERTUMBUHAN DAN PRODUKSI BEBERAPA GENOTYPE JAGUNG (Zea mays L.) CALON HIBRIDA UMUR GENJAH DAN VARIETAS PEMBANDING BIMA 7 PADA JARAK TANAM YANG BERBEDA

This research was conducted with the aim of: 1) To observe growth and production of maize genotypes hybrid candidate early age, 2) Determine optimal spacing that will result in maximal production of genotype hybrid candidate early maturing and 3) To know interaction between maize genotypes hybrid candidate of early maturing and plant spacing. Research was conducted on dry land located in Bajeng, Gowa, South Sulawesi. Research was conducted from April to July 2017 using Split Plot Design method. As the main plot is the maize genotype consisting of 3 genotypes: ST201328, ST201359, ST201312 and varieties comparison Bima 7 while for sub plot is treatment the various spacing between two levels are: 60 cm x 20 cm and 50 cm x 20 cm. Treatment combination was repeated three times as a block to obtain 24 experimental units. The results of this research show that: 1) Maize genotype ST201328 is maize early maturing hibrid has appearance shortest plant, fastest flowering male age as well flowering female, smallest Anthesis Silking Interval (ASI), fastest harvest age and longer cob. Genotype ST201312 has appearance highest plant, greatest Anthesis Silking Interval, greatest Leaf Area Index and longest cob. 2) Plant spacing 50 cm x 20 cm obtained high Leaf Area Index and highest location cob. Average highest production dry seeds on plant spacing 50 cm x 20 cm for all maize genotypes tested. 3) Interaction that happaned between maize genotype ST201312`on plant spacing 60 cm x 20 cm obtained longest cob is 18,07 cm and differs markedly with varieties comparison Bima 7. Maize genotype ST201312 on plant spacing 50 cm x 20 cm obtained yield dry cheeks is amount 10,58 ton ha–1.

Performance of common buckwheat (Fagopyrum esculentum M.) in response to row spacing under ridge and furrow cropping systems in a semiarid region of China

ABSTRACTRidge and furrow systems as well as the wide-narrow row spacing are recognized as good management practices in crop production. To obtain some available information concerning the suitable agricultural practices for buckwheat cultivation in arid and semi-arid area, a two-year field study was conducted to investigate the performance of common buckwheat grown under six cropping patterns: conventional flat single/double row planting (NS/ND); furrow single/double row planting (FS/FD); ridge single/double row planting (RS/RD); single row planting with equal row spacing and double row planting with wide-narrow row spacing practice. Plants grown under the FD system exhibited higher water use efficiency (WUE) and rainfall use efficiency (RUE) than plants cultivated with the NS system, increases with 13.7% and 21.9%, respectively, in 2014, while 9.8% and 14.0%, respectively, in 2015. Plants of the FD system also displayed the greatest leaf area index and canopy openness at growth stage of 40, 60, and 80 days after sowing, maximum biomass production (13.96 t ha−1) and grain yield (3486.2 kg ha−1) in 2014, and the least pronounced soil nitrate consumption as compared to plants from other tillage systems. We conclude that FD is the optimum planting pattern for common buckwheat cultivation in semi-arid and arid environments.

Comparison of agronomic performance between inter-sub-specific hybrid and inbred japonica rice under different mechanical transplanting methods

Mechanical transplanting has been applied to rice cultivation to save labor costs and ease labor shortages in Asian countries, especially in China. However, little information is available related to the characteristics of agronomic performance when comparing inter-sub-specific hybrid rice (IHR) and inbred japonica rice (IJR) under mechanical transplanting method. In 2013 and 2014, field experiments were conducted using IHR (Yongyou 2640) and IJR (Wuyunjing 24) under two cultivation patterns, that is, pot seedlings mechanically transplanted (PS) and carpet seedlings mechanically transplanted (CS). Grain yield, yield components, leaf area index (LAI), leaf area duration (LAD), aboveground biomass, crop growth rate (CGR), nitrogen (N) uptake, and N accumulation were investigated. When compared with CS, PS displayed significantly increased grain yield for both varieties because the larger sink size allowed higher N accumulation from panicle initiation to maturity. Moreover, total aboveground biomass under PS increased significantly compared with that under CS; that is, higher photosynthetic productivity resulted from a greater LAI and higher LAD during the grain filling stage. Higher N absorption capacity in the middle and late growth periods resulted in significantly enhanced total N uptake under PS. When compared with IJR for both treatments, IHR generated 75.2% more grain yield. However, the characteristics creating high yield of IHR were different from those of IJR. Greater aboveground biomass production as well as higher N uptake and accumulation created higher grain yield in IHR than in IJR. These results suggest higher yield could be achieved using PS with IHR, attributing to exploit both yield superiority and productive potential.

Impact of grassland conversion to forest on groundwater recharge in the Nebraska Sand Hills

Study regionNebraska National Forest in the High Plains Aquifer, Nebraska Sand Hills, U.S.A. Study focusThis research aimed to investigate the effects of grassland conversions to forest on recharge rates in a century-old experimental forest. The DiffeRential Evolution Adaptive Metropolis (DREAMZS) global optimization algorithm was used to calibrate the effective soil hydraulic parameters from observed soil moisture contents for 220 cm deep uniform soil profiles. The historical recharge rates were then estimated by applying the numerical model HYDRUS 1-D for simulation of two plots representing grasslands and dense pine forest conditions. New hydrological insightsThe results indicate that conversion from grasslands to dense pine forests led to vegetation induced changes in soil hydraulic properties, increased rooting depth, and greater leaf area index, which together altered the water budget considerably. The impacts of land use change, expressed in percent of gross precipitation, include a 7% increase in interception associated with an increase in leaf area index, a nearly 10% increase in actual evapotranspiration, and an overall reduction of groundwater recharge by nearly 17%. Simulated average annual recharge rates decreased from 9.65 cm yr−1 in the grassland to 0.07 cm yr−1 in the pine plot. These outcomes highlight the significance of the grassland ecology for water resources, particularly groundwater recharge, in the Nebraska Sand Hills and the overall sustainability and vitality of the High Plains Aquifer.

Analysis of Leaf Area Index Dynamic and Grain Yield Components of Intercropped Wheat and Maize under Straw Mulch Combined with Reduced Tillage in Arid Environments

<p class="2">Knowledge on effect of yield formation under straw combined with plastic film mulch is important in highlighting the importance of cultivating high-efficient and high-yield crops in the arid environments. In this study, we developed a ‘double-mulching’ system, i.e., plastic film coupled with straw mulch, integrated together with intensified strip intercropping. We determined (i) the responses of leaf area index improvement to the integrated double mulching system, and (ii) Its effects on yield formation process and mechanism of intercropped wheat and maize under the integrated systems. Experiments were carried out in northwest China in 2009 to 2011. Results showed that wheat-maize strip intercropping in combination with plastic film and straw covering on the soil surface (i.e., NTS) increased maize yield by 27 to 42% compared to conventional monoculture maize, and increased wheat yield by 149 to 160% compared to conventional monoculture wheat. The crops on NTS had higher harvest index of maize, an increase of 8.2 to 21.6% than that of conventional monoculture maize. NTS system increased spike number (i.e., SN) by an average of 30.4%, increased kernel number per spike (i.e., KNS) by an average of 10.8%, and increased thousand-kernel weight (i.e., TKW) by an average of 7.0% of intercropped wheat in comparison with conventional monoculture wheat. Similarly, there was an average increase of 5.7% of SN, 23.8% of KNS, and 7.5% of TKW under intercropped maize in comparison with conventional monoculture maize. Moreover, the treatment on NTS had greater leaf area index (i.e., LAI) an average increase of 64.1% than that in conventional monoculture maize. Similarly, LAI had an average increase of 29.3% than conventional monoculture wheat. Path analysis exhibited that straw mulching combined with reduced tillage increased the grain yield of intercropped wheat by improving KNS, and increased the grain yield of intercropped maize by improving SN. We conclude that the intercropping system in combination with plastic film and straw mulching can be an effective system for boosting crop productivity via improving yield components and LAI under limited resources in arid enviroments.</p>

Primary Growth Parameters of Three Alfalfa Cultivars Adapted to Highland Climatic Conditions

AbstractAn irrigated field study was conducted to determine the relative importance and inter‐relationships of growth parameters of three dormant alfalfa (Medicago sativa L.) cultivars grown in the highlands of Eastern Anatolia, Turkey, in 2000–2003. The fast‐growing cultivar Savas had the greatest dry matter (DM) yield at the final sampling date with the greatest mean crop growth rate. In addition to a greater relative growth rate (RGR), this cultivar had more stem branching and greater leaf area in the canopy, which resulted in greater leaf area index (LAI) and greater leaf area duration. Despite the considerable increase in leaf area ratio (LAR: leaf area per unit shoot DM), the reduction in RGR of all cultivars over time was the result of a large decline in net assimilation rate (NAR) due to increasing specific leaf area (SLA). Intracultivar variation in the RGR of alfalfa is mainly determined by NAR and SLA, and both were significantly higher for Savas than the other two cultivars. The relative importance of NAR and SLA to RGR changed due to increasing self‐shading as the LAI of the canopy increased, creating a trade‐off between NAR and SLA.

Effect of understory management on phenological responses of eastern black walnut on an alluvial Arkansas soil

Black walnut (Juglans nigra L.) is commonly grown in agroforestry practices for nuts and/or timber with little knowledge of how understory herbage management might affect tree phenology. We compared black walnut plant type (variety and wild-type) for phenological response in date of budburst, leaf area index (LAI), quantum yield of photosystem II (Fv/Fm), radial stem growth, and total chlorophyll concentration in response to understory herbage N fertilization and herbage suppression in an agroforestry practice on an alluvial soil. Herbage treatments generally had little impact on phenological responses, although N fertilization increased herbage yield that delayed budburst. Radial stem growth commenced at about budburst (mid-April) and virtually ceased in late October, about 30 days before leaf drop. Early-season radial stem growth was greater for the wild-type than the variety, while the variety had more rapid late-season growth. The wild-type had consistently greater LAI than the variety at any given day-of-year (DOY), and usually had greater LAI than the variety regardless of herbage treatment. Leaves of both plant types maintained a high Fv/Fm during most of the growing season, but total chlorophyll concentration decreased across DOY regardless of plant type. N fertilizer should be applied with understory herbage suppression to avoid delay of budburst. Further study is needed of phenological responses during longer growth periods, or as affected by latitude, soil water, and soil fertility.