Low Irrigation Levels Research Articles

MAXIMIZING THE PRODUCTIVITY AND WATER USE EFFICIENCY OF TOMATO PLANTS (LYCOPERSICON ESCULENTUM MILL.) CULTIVATED IN THE NEW RECLAIMED LANDS USING DIFFERENT IRRIGATION WATER QUANTITIES AND SOME WATER SAVING SUBSTANCES

Egypt is one of the countries facing great challenges due to its limited water resources, so it has become necessary to study the best ways to rationalize irrigation water use and maximizing the efficient use of water under those circumstances. Two field experiments were conducted at a private farm at Al-Nubaria region, Behira Governorate, Egypt, during the two successive seasons of 2011 and 2012, to investigate the effect of three irrigation water quantities (2400, 1800 and 1200 m3 fed-1) and some water saving substances, i.e., control, zeolite, super absorbent polymer and K-humate as well as their interactions on growth, chemical composition, yield, water use efficiency and fruit quality of tomato plants (Jacal F1 hybrid) cultivated under drip irrigation system in new reclaimed lands during early summer season. The obtained results indicate that: - Increasing water quantity applied to tomato plants up to the highest used level (2400 m3 fed-1) significantly increased vegetative growth characters, i.e., stem diameter, foliage fresh weight, leaf area and leaf relative water content as well as total N, P and K uptake by tomato plants. On the other hand, total chlorophyll contents enhanced significantly with decreasing irrigation water supply. Tomato yield characters, i.e., number of fruits per plant, average fruit weight and total yield increased with increasing irrigation water quantity up to 2400 m3 fed-1. The medium irrigation water level (1800 m3 fed-1) recorded the highest values of water use efficiency. Under the low level of irrigation water (1200 m3 fed-1) tomato fruit quality characters, i.e., flesh firmness, lycopene, TSS and total soluble sugars recorded the highest significant values. - Soil application of K-humate led to the significant increases in all vegetative growth traits, total NPK uptake, total chlorophyll, yield characters and water use efficiency as well as tomato fruit quality characters compared to soil application of zeolite, super absorbent polymer and control. - Tomato vegetative growth characters were significantly affected by the combination of 2400 m3 fed-1 and K-humate soil application. Applying 2400 or 1800 m3 fed-1 of irrigation water combined with soil application of K-humate resulted in the highest significant NPK uptake as well as all studied tomato yield characters. Soil application of K-humate combined with the low irrigation level (1200 m3 fed-1) showed the highest significant chlorophyll contents in tomato leaves. Water use efficiency showed the highest value using the medium level of irrigation water (1800 m3 fed-1) combined with the soil application of K-humate as compared to the other treatments. Soil application of K-humate combined with the medium irrigation water level (1800 m3 fed-1) or the low level (1200 m3 fed-1) recorded the highest values of tomato fruit quality characters. Using the medium irrigation level (1800 m3 fed-1) combined with the soil application of K-humate obtained the highest net return and returned the highest benefit-cost ratio (3.48) in comparison with other treatments. It could be concluded that irrigation tomato plants with 1800 m3 fed-1 combined with soil application of K-humate (2 kg fed-1 in every addition, 4 times during the season) incorporated with drip irrigation system could be recommended to improve yield and quality of tomato plants as well as maximizing the water use efficiency by tomato plants, saving about 25% of the total used irrigation water quantity commonly used in tomato production. Such treatment is found to be economically and more agronomically feasible and can be recommended under drip irrigation system in sandy soil in new reclaimed lands, giving the highest net return and benefit-cost ratio to the farmers.

Yield and quality of head lettuce after 24-epibrassinolide application under optimal and reduced irrigation

The aim of this work was evaluation of 24-epibrassinolide influence on yield and quality of head lettuce in optimal and reduced moisture conditions and work out recommendation of 24-brassinosteroids use for lettuce in growers praxis. Field trials were carried out on land belonging to the Demonstration and Research Station of CULS in Prague – Troja in 2009 and 2011. Planting on 27. 8. 2009 and 20. 8. 2011 was done at planting space 0.25 × 0.30 m, each variant in four repetition (single plot 4,5 m2). Seedlings of head lettuce (cultivar Santoro – Rijk Zwaan) were used. Irrigation was carried out by microspraying, and was based on current values of efficient water capacity (EWC); the critical value of the EWC was 80% for optimally irrigated fields (irrigation O), and 50% for variants with reduced levels of irrigation (irrigation S). The total amount of irrigation water during vegetation were as follows: the variant with optimal levels of irrigation (O) had 131 mm in 2009 and 123 mm in 2011; the variant with reduced levels of irrigation (S): 58 mm in 2009 and 63 mm in 2011 Three variants were in both (O and S) conditions: A – no application of 24-epibrassinolide, B – 1 × 24-epibrassinolide application immediately after planting, and C – application of 24-epibrassinolide 2 x (immediately after planting and then after 14 days after 1st application). Concentration of 24-epibrassinolide was 10−6. Following parameters of head lettuce were set after harvesting (10.–12. 10. 2009 and 14.–15. 10. 2011): weight of single heads, marketable heads, marketable yield (in pcs/ha and t/ha) and ascorbic acid and nitrate contents. Influence of 24-epibrassinolide on single lettuce head weight was not significant, decrease of head weight was evident after 24-epibrassinolide application in some variants. Significant increase of marketable heads number and their percentages were noted after 24-epibrassinolide application in optimal moisture conditions – in variant B of 12 261 heads/ha (11.1 %) and in variant C of 16 279 heads/ha (14.7 %) compared with non treated variant A. This trend was not visible in reduced moisture conditions. Increase (nonsignificant) of total marketable yield (in t/ha) was noted after 24-epibrassinolide application. No significant differences were founded among the ascorbic acid contents in each irrigation variant. A higher ascorbic acid content (by approximately 11.9 % in variant C compared with control A) is evident after application of 24-epibrassinolide in the variant with lower levels of irrigation – S. Contrarily, decrease ascorbic acid content is indicated in the optimal levels of irrigation – O (by approximately 16.8 % in variant C compared with control A). The influence of 24-epibrassinolide application on the nitrate content was not significant, but the trend of nitrates decrease in optimal irrigation conditions is evident.

Yield and quality of sweet corn under deficit irrigation

The present study was conducted to determine the effects of different irrigation levels (I100: full irrigation; I85: 15% deficit; I70: 30% deficit; I55: 45% deficit and I40: 60% deficit) on yield and yield components, sugar and protein content of fresh sweet corn during the years of 2011 and 2012. Experiments were carried out in a randomized complete-block design with three replications.The lowest and the highest plant water consumptions (Et) were found in I40 (240–406mm) and I100 (348–504mm) treatments in both years. Water deficit affected on maize fresh ear yields, yield components, quality and water use efficiencies. The lowest fresh ear yields (11515.7 and 10952.3kgha−1) were determined in I40 treatments in both years, respectively. The highest fresh ear yields (14857.7 and 14712.7kgha−1) were obtained from I100 treatments in 2011 and 2012 years, respectively.Maize fresh ear yields were significantly affected by water deficits. Low irrigation levels decreased the ear yields. However, it was clearly observed that I70 treatment could be a water-saving treatment without a significant decrease in yield. In addition, the highest protein content and sugar amount was also observed in I70 treatment. I70 treatment seems to have lowest impact on yield and higher quality for sweet corn.

Evaluation of deficit irrigation for efficient sheep production from permanent sown pastures in a dry continental climate

Deficit irrigation can be a useful management tool to increase water productivity of forage and sheep production from pastures in water deprived areas of the world. A three year study compared sheep production from permanent sown pastures on clay–loam soil in a dry continental climate that were irrigated at four levels in Konya, Central Anatolia Region of Turkey. Pastures were established in 2007 with red fescue (Festuca rubra L.), Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), white clover (Trifolium repens L.) and birdsfoot trefoil (Lotus corniculatus L.) and irrigated with 100 (optimum irrigation), 75, 50 or 25% of their full irrigation requirement. Established pastures were grazed rotationally by flocks of weaned lambs between 2008 and 2010. Liveweight gain was approximately 2kgha−1d−1 from the 100 and 75% irrigation treatments. However, lower levels of irrigation caused reductions (P<0.01) in liveweight gains with animals gaining less than 1kgha−1d−1 in the 25% irrigation treatment. Average total annual animal liveweight production was 498, 445, 380 and 198kgha−1 for 100, 75, 50 and 25% irrigation treatments, respectively. The water productivity of the full irrigation treatment per unit of dry matter and meat produced was low, particularly during the summer months, and it increased with deficit irrigation. Deficit irrigation between 50 and 75% of the full requirements during late spring and summer, prior to de-stocking, can provide efficient use of water when water resources are limited. The level of irrigation can be reduced further during the late summer and autumn when stocking rates and the demand for feed or energy from pastures are lower.

Evaluation of seed cotton (Gossypium hirsutum L.) production and quality in relation to the different irrigation levels and two row spacings

The effect of row spacings and irrigation levels on the earliness of seed production of cotton was investigated under the Mediterranean environment of central Greece. This particular cotton growing area is exposed to risk of autumn rainfall that might cause low seed quality in fields allocated primarily for seed production. Two varieties of cotton, Celia and Hersi, were planted in two row spacings (93 and 75 cm) and two irrigation levels (normal and low levels 6160 and 3080 mm ha -1 ). No significant difference in the yield was found among the two varieties, nor between the two row spacings. The low irrigation level had significantly negative effects on the number of squares, bolls, total dry weight and seed cotton production when compared with irrigation level. However, the low irrigation level resulted in a harvest earlier by ten days, which contributed to avoiding autumn rainfall. Seed quality (measured by germination and Warm-Cold Vigour Index Test) was better in seeds from the low irrigation level than in those from the normal irrigation level. Although yield of both varieties was higher under normal irrigation, seed quality was lower compared to low irrigation level. This was evidenced by the higher Free Fatty Acid (FFA) in “normally” irrigated plants. The results of this study showed that low irrigation level offers substantial benefits for early harvesting and production of high seed quality. Moreover, the FFA could be successfully employed as a quick criterion for seed quality ranking.

Mitigating Cotton Revenue Risk Through Irrigation, Insurance, and Hedging

This study focuses on managing cotton production and marketing risks using combinations of irrigation levels, put options (as price insurance), and crop insurance. Stochastic cotton yields and prices are used to simulate a whole-farm financial statement for a 1,000 acre furrow-irrigated cotton farm in the Texas Lower Rio Grande Valley under 16 combinations of risk management strategies. Analyses for risk-averse decision makers indicate that multiple irrigations are preferred. The benefits to purchasing put options increase with yields, as they are more beneficial when higher yields are expected from applying more irrigation applications. Crop insurance is strongly preferred at lower irrigation levels.

Climate forcing and desert malaria: the effect of irrigation

BackgroundRainfall variability and associated remote sensing indices for vegetation are central to the development of early warning systems for epidemic malaria in arid regions. The considerable change in land-use practices resulting from increasing irrigation in recent decades raises important questions on concomitant change in malaria dynamics and its coupling to climate forcing. Here, the consequences of irrigation level for malaria epidemics are addressed with extensive time series data for confirmed Plasmodium falciparum monthly cases, spanning over two decades for five districts in north-west India. The work specifically focuses on the response of malaria epidemics to rainfall forcing and how this response is affected by increasing irrigation.Methods and FindingsRemote sensing data for the Normalized Difference Vegetation Index (NDVI) are used as an integrated measure of rainfall to examine correlation maps within the districts and at regional scales. The analyses specifically address whether irrigation has decreased the coupling between malaria incidence and climate variability, and whether this reflects (1) a breakdown of NDVI as a useful indicator of risk, (2) a weakening of rainfall forcing and a concomitant decrease in epidemic risk, or (3) an increase in the control of malaria transmission. The predictive power of NDVI is compared against that of rainfall, using simple linear models and wavelet analysis to study the association of NDVI and malaria variability in the time and in the frequency domain respectively.ConclusionsThe results show that irrigation dampens the influence of climate forcing on the magnitude and frequency of malaria epidemics and, therefore, reduces their predictability. At low irrigation levels, this decoupling reflects a breakdown of local but not regional NDVI as an indicator of rainfall forcing. At higher levels of irrigation, the weakened role of climate variability may be compounded by increased levels of control; nevertheless this leads to no significant decrease in the actual risk of disease. This implies that irrigation can lead to more endemic conditions for malaria, creating the potential for unexpectedly large epidemics in response to excess rainfall if these climatic events coincide with a relaxation of control over time. The implications of our findings for control policies of epidemic malaria in arid regions are discussed.

Padrão de distribuição de K+, Ca++, Mg++ e P no solo de um pomar de citros em função da fertirrigação

Em solos tropicais, a distribuição dos nutrientes no solo em função da fertirrigação realizada por meio de irrigação localizada (gotejamento e/ou microaspersão), na cultura de citros, é pouco conhecida. Este trabalho teve por objetivo avaliar os padrões de distribuição de potássio, cálcio, magnésio e fósforo em solo tropical, em função da fertirrigação, aplicada por dois sistemas de irrigação localizada (microaspersão e gotejamento), sendo que o sistema por gotejamento era composto por uma e duas linhas laterais por linha de plantas, e o de microaspersão por apenas uma linha, e com três dotações hídricas (100%, 75% e 50%) da evapotranspiração da cultura (ETc), em um pomar de laranjeira. As fontes de fertilizantes utilizadas na fertirrigação foram o nitrato de amônio (fonte de N), o cloreto de potássio (fonte de K+) e o ácido fosfórico (fonte de P). Observouse que, sob o emissor, nos tratamentos com gotejamento, houve depleção nos teores de Ca++ e Mg++ desde a superfície do solo até 60 cm de profundidade em relação aos teores anteriores às fertirrigações, enquanto os teores de P aumentaram, principalmente na camada de 0 cm a 20 cm. Na microaspersão, esses efeitos não foram observados, ocorrendo distribuição mais homogênea desses nutrientes tanto na direção transversal à linha de plantas quanto em profundidade. As lâminas de irrigação aplicadas por irrigação localizada não interferem na distribuição de K+ aplicado por fertirrigação e do Ca++ e Mg++ no solo em profundidade, porém menores lâminas de irrigação promovem maior concentração de P na camada mais superficial do solo, e lâminas maiores carregam o P para camadas mais profundas.

Water relations of olive trees cultivated under deficit irrigation regimes

The experiment was carried out at the Experimental Field ‘Taoues’, southern Tunisia (34°N, 10°E) to examine the effect of irrigation schedules on water relations for young olive trees, cultivars Chétoui, Chemlali, Coratina, Picholine and Manzanille. Plants were cultivated at 7 m × 7 m spacing and drip irrigated from April to September. Irrigation amounts (IA) of 20%ET c, 50%ET c and 100%ET c were applied, where ET c is the FAO crop evapotranspiration. The effect of IA on midday leaf water potential ( Ψ leaf), stomatal resistance ( R s) and conductance ( g s), soil ( H v) and relative leaf (RWC) water contents was studied. Results showed that a further increase in IA was not systematically followed by an increase of water potential, production and WUE values. Some controversial responses were observed following to a variety with large seasonal variations. At the beginning of the growing season, differences between treatments were not very important because soil water content was still high enough to prevent important changes in Ψ leaf values. The most stressed trees showed potentials of −1.53 MPa for Picholine cv. and ranging between −2.30 MPa and −2.10 MPa for the other varieties depending on IA. The less stressed trees provided potentials of −0.97 MPa for Picholine cv. and varying between −1.63 MPa and −2.13 MPa for cultivars Coratina, Manzanille, Chétoui and Chemlali. Then, as the season progresses, and when IA was increased from 20%ET c to 50%ET c, Ψ leaf values decreased significantly for cultivars Chemlali (−3.05 MPa), Coratina (−3.75 MPa), Manzanille (−3.0 MPa) and Chétoui (−3.5 MPa). At 100%ET c, Manzanille and Picholine cultivars show better water status with respective potentials of −2.7 MPa and −2.6 MPa. Stomatal resistance monitoring showed maximums at midday for all cultivars with pick value of 4.45 s/cm recorded for Chétoui cultivar irrigated at 50% ET c. The most important variations were recorded for cultivar Chemlali which seem to be the ablest to regulate stomata aperture. Close coordination between Ψ leaf and g s and Ψ leaf and RWC measurements was found. But, the response varied following to treatment. At low irrigation levels (20%ET c and 50%ET c), g s was found to be linearly and positively correlated to Ψ leaf. It increased linearly and positively with increasing values of Ψ leaf ( r of 0.84 and 0.96, respectively). At 100%ET c, Ψ leaf is found to be correlated to g s following to a polynomial function with an optimum g s value of 450 mmol/m 2/s and Ψ leaf of about −2.5 MPa.

Studies Regarding Biometric Characteristics of Lettuce (Lactuca sativa L.), Grown at Different Rates of Irrigation

Many vegetable species are shallow-rooted and sensitive to mild water stress. A possibility for improving water use is better management of water application, but that’s require information on detailed seasonal changes in crop growth and on root distribution and root extraction of soil water that is not currently available for most vegetable crops. In lettuce, where the harvested part of the plant is the photosynthetic leaf area, it is especially important to maintain optimal growth through the application of water and nutrients (GALLARDO et al, 1996). The experiments were made in bifactorial sequences, in spring of year 2006, placed in the vegetable field glasshouse, from USAMV Cluj-Napoca. The main purpose was to study the watering regime influence on the yield level and the quality of lettuce. The experiment included drip irrigation and microsprinkler irrigation, with three irrigation water levels (60, 70 and 80 % from activ humidity interval). Harvested plants from each variant were evaluated immediately according to yield, plant height, head diameter, leaf number and dry matter. Plant weight (g), head diameter (cm) and plant height (cm) were measured by caliper rule and calculated as the average of measured values. The average leaf number per plant was calculated by counting the leaves, and the dry matter amount was found after drying at 85 o C in 48 hours. Data show that differences due to water regime, irrigation method and the interaction between water regime and irrigation methods were highly significant for both, yield and water use efficiency. At high irrigation levels (80% AHI), yield were high (30 t/ha with dripline) and decreased significantly (23,2 t/ha with microsprinklers) at low irrigation levels (60% AHI). We can draw the conclusion that for lettuce culture in protected area, the best irrigation method is drip irrigation. The microsprinklers with special sprayer are not giving the best results in protected area, because of higher evaporation losses, higher humidity, the wet foliage which increases the potential for diseases, recording a percent of 20 % perished plants. The significant increases in dry matter were found as parallel to irrigation water deficit and the highest and lowest dry matter were found at 60% AHI irrigation level and 80% from AHI, respectively. This may be attributed to higher plant weight observed from 80% AHI treatment than those of deficit irrigation treatments. In other words, when the leaves were desiccated relative difference was bigger. Applying a different watering method for lettuce cultivated in protected areas, influences the plant growth, and so the production obtained. Developing the humidity condition from soil, that means any growing minimal level of watering applying with 10% from IUA caused a growing production. REFERENCES

Policy interventions needed to manage bacterial build-up in municipal effluent irrigated agroforestry plantations

Mortality of total enteric bacteria, Escherichia coli, other coliforms and Salmonella spp. was monitored under municipal effluent irrigated agroforestry plantations via periodic field and in vitro studies. The results of the field study showed no significant differences among agroforestry systems in any of the monitored bacterial populations. Microbial populations were higher in summer (January 2003) than in other seasons. The in vitro study, two pot experiments during October 2003 (pre-summer) and July 2004 (winter), revealed significant effects of moisture on Most Probable Number (MPN) of the total bacteria and E. coli. The moisture levels did not affect the Salmonella spp. and other coliform bacteria, suggesting that certain microbes may be found at low irrigation levels and vice-versa. Enteric microbes were recorded until the 27th day after irrigation in October 2003 and for less than 15 days in July 2004. Thus inclusion of more pathogens in environmental guidelines and stringent exercise of the 'exclusion' in practice are suggested.

Economic Analysis of Subsurface Drip Irrigation System Uniformity

As more subsurface drip irrigation (SDI) systems are being installed throughout the plains of Texas for cotton production, irrigators are concerned about the high cost of installation and the potential benefits of alternative designs. A field study was conducted at the Texas AgriLife Research facilities at Halfway, Texas, to document the agronomic impacts of distribution uniformities on cotton production over a six year period. Based on this study, a net present value analysis of SDI systems having different irrigation uniformities was conducted. The authors considered six scenarios that represent six treatments of the field study. The scenarios included three water distribution uniformities represented by flow variations of 5%, 15%, and 27%, with each irrigated at two levels, a base irrigation amount and 60% of the base irrigation amount. Net present values were calculated for each level of uniformity and irrigation level. At the lower irrigation level, the least uniform design provided a higher net present value. The length of the planning horizon affected NPV with the more uniform system having a better NPV at the longer planning horizon due to the cumulative effect of small improvements in net income over the longer time. In addition, the producer's risk aversion level affected their choice of design uniformities. A more risk averse producer preferred a more uniform design and was willing to pay a higher installation cost for a more uniform system. A less risk averse producer preferred a less uniform system design with a lower initial cost.

Influence of moisture on the growth and biomass allocation in Haloxylon ammodendron and Tamarix ramosissima seedlings in the shelterbelt along the Tarim Desert Highway, Xinjiang, China

The authors studied the effects using three different levels of irrigation on the growth and biomass allocation in H. ammodendron and T. ramosissima seedlings in the shelterbelt along the Tarim Desert Highway. The three irrigation amounts were 35 (CK), 24.5 (treatment 1), and 14 (treatment 2) kg·ind. plant−1·once−1, respectively. The results show that (1) the vertical depth of the two seedlings’ root increased with lower levels of irrigation showing that the two species adapted to decreased irrigation by root elongation in the hinterland of the Taklimakan Desert, and the vertical root depth of H. ammodendron under treatment 2 was notably higher than CK. (2) Compared with CK, the belowground biomass of treatment 1 and 2 both showed a significant increase as follows: H. ammodendron seedlings increased by 14.51% and 37.03% under treatment 1 and 2, respectively, while T. ramosissima seedlings increased by 68.19% and 25.78% under treatment 1 and 2, respectively. This means that H. ammodendron seedlings were more adapted to the conditions in treatment 2 while T. ramosissima seedlings were better adapted to treatment 1 conditions. (3) When compared with CK, the fine root bomass of these two species all exhibited some increase under both treatments, and ANOVA analysis showed that the biomass of deep layer root of the two species under treatment 2 was notably higher than CK and treatment 1. This should help seedlings to more effectively absorb soil water from deep layers during dry conditions. (4) The root-shoot ratio was different for these two species. For H. ammodendron seedlings, the root-shoot ratio was less than 1, while for T. ramosissim seedlings it was larger than 1. The root-shoot ratio of H. ammodendron seedlings increased with decreasing levels of irrigation, and that of T. ramosissim seedlings also increased under treatment 2. (5) With decreasing levels of irrigation, due to the difference of species, the growth variation of aboveground indexes was also different, while compared with CK, it was not significant.

Impact of moisture and UV degradation on Beauveria bassiana (Balsamo) Vuillemin conidial viability in turfgrass

Abstract Beauveria bassiana conidial viability in turfgrass was evaluated using a two-component nucleic acid stain and fluorescence microscopy. Turfgrass samples along with the top 5 cm of soil were used for conidial extraction and viability evaluation on 1, 2, 3, 7, 14 and 21 days after treatment. There were no differences in conidial viability between two Orthoptera strains, 3622 and 5977, and both strains were able to persist in a sandy loam soil for up to three weeks after application. High and low irrigation levels were applied to each of the two strains and results show that higher irrigation (5.1 cm/week) maintains conidial viability better than a low irrigation level (2.5 cm/week). Mean conidial viability was approximately 8–12% greater in plots with the high irrigation regime. Rather than significantly increase soil moisture levels, it is hypothesized that the greater amount of irrigation helps to move the conidia deeper into the thatch layer and soil profile, an area that provides protection from damaging surface temperatures and UV exposure. Rainfall that occurred during the beginning of the 2005 test minimized the irrigation effect, and the irrigation treatment differences were more pronounced after 48 h. Four different UV protectants were evaluated for an impact on conidial viability of strain 3622. Two protectants, an optical brightener and magnesium silicate clay, when added to an emulsifiable oil formulation, significantly increased conidial viability on all evaluation dates. The clay particles act as a sunlight blocker while the optical brightener absorbs UV light. The combined protection from the oil and the additive increased conidial viability by approximately 10% on all evaluation dates. Results from this study provide insight into ways to increase entomopathogenic fungal viability under field conditions.

Water-nitrogen relationships for wheat growth and productivity in late sown conditions

Field experiments were conducted on a sandy loam soil (Typic Ustochrept) to study the water-nitrogen –yield relationships of late sown wheat under adequate and limited water supply conditions. The treatments comprised of four levels of irrigation (I 0 , no post-sown irrigation; I 1 , one irrigation at CRI stage; I 2 , two irrigations, each at CRI and flowering stages; I 3 , four irrigations each given at CRI, jointing, flowering and dough stages) in main plots and a combination of three N levels (0, 50 and 100 kg N/ha) and two levels of zinc as ZnSO 4 . 7H 2 O (0 and 5 kg Zn/ha) in sub-plots of a split plot design and were replicated three times. Progressive increase in irrigations from 0 to 4 and nitrogen levels from 0 to 100 kg/ha, increased the average LAI, CGR, RGR and NAR, yield attributes, wheat biomass and grain yield significantly (p ≤ 0.05) over the control (I 0 and N 0 ), in both the seasons, respectively. Analyses by multiple regression techniques reveled that LAI estimates with N uptake were much higher at 84% predictability than the estimate based on water use that could account for 75% of the variations only. Lower levels of water consumption by crop were seen to result in less leaf area therefore, resulting in lower biomass and grain yields at lower levels of irrigation. The highest rate of biomass gains of 53.1 kg/ha-mm was obtained during the 60–90 day period, a period that fell within the maximum growth phase of wheat, followed by 28.3 and 6.7 kg/ha-mm during 90-120 and 0-60 days after sowing (DAS) periods. The response of the above ground biomass to nitrogen uptake was higher (76.6 kg/ha-kg N uptake) during 60-90 DAS period than during the 0-60 DAS period (22.1 kg/ha-kg N uptake). Additive production functions therefore, took care of the stage sensitivity along with the complete water and nitrogen stresses as induced through different applications of water and nitrogen. The maximum growth rates in wheat were commensurate with highest levels of water use as well as nitrogen use observed during the 60-90 DAS period of growth. For this reasons, scheduling of water and nitrogen application ought to consider providing relatively less quantities of water during the 0-60 DAS period as compared to the 90-120 and 60-90 DAS periods respectively, in order to provide just sufficient amounts of water so as to enhance the uptake of available nitrogen required for optimum growth and development of wheat. Journal of Agriculture Science and Technology Vol. 7(1) 2005: 1-17

Water–nitrogen relationships for wheat growth and productivity in late sown conditions

Field experiments were conducted on a sandy loam soil (Typic Ustochrept) to study the water–nitrogen yield relationships of late sown wheat under adequate and limited water supply conditions. The treatments comprised of four levels of irrigation ( I 0, no post-sown irrigation; I 1, one irrigation at CRI stage; I 2, two irrigations, each at crown root initiation (CRI) and flowering stages; I 3, four irrigations each given at CRI, jointing, flowering and dough stages) in main plots and a combination of three N levels (0, 50 and 100 kg N/ha) and two levels of zinc as ZnSO 4·7H 2O (0 and 5 kg Zn/ha) in sub-plots of a split plot design and were replicated three times. Progressive increase in irrigations from 0 to 4 and nitrogen levels from 0 to 100 kg/ha, increased the average leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR) and net assimilation rate (NAR), yield attributes, wheat biomass and grain yield significantly ( p ≤ 0.05) over the control ( I 0 and N 0), in both the seasons, respectively. Analyses by multiple regression techniques reveled that LAI estimates with N uptake were much higher at 84% predictability than the estimate based on water use that could account for 75% of the variations only. Lower levels of water consumption by crop were seen to result in less leaf area therefore, resulting in lower biomass and grain yields at lower levels of irrigation. The highest rate of biomass gains of 53.1 kg/ha-mm was obtained during the 60–90 day period, a period that fell within the maximum growth phase of wheat, followed by 28.3 and 6.7 kg/ha-mm during 90–120 and 0–60 days after sowing (DAS) periods. The response of the above ground biomass to nitrogen uptake was higher (76.6 kg/ha-kg N uptake) during 60–90 DAS period than during the 0–60 DAS period (22.1 kg/ha-kg N uptake). Additive production functions therefore, took care of the stage sensitivity along with the complete water and nitrogen stresses as induced through different applications of water and nitrogen. The maximum growth rates in wheat were commensurate with highest levels of water use as well as nitrogen use observed during the 60–90 DAS period of growth. For this reasons, scheduling of water and nitrogen application ought to consider providing relatively less quantities of water during the 0–60 DAS period as compared to the 90–120 and 60–90 DAS periods respectively, in order to provide just sufficient amounts of water so as to enhance the uptake of available nitrogen required for optimum growth and development of wheat.

Efeitos da fertirrigação sobre a produção de palmito da pupunheira

Com o objetivo de avaliar o efeito da aplicação de lâminas de irrigação e níveis de adubação nitrogenada na produção de palmito de pupunheira (Bactris gasipaes Kunth), foi conduzido um experimento a campo, durante 22 meses, em Piracicaba (SP). Empregou-se o delineamento em blocos casualizados, com tratamentos distribuídos em esquema fatorial 3 (nitrogênio) x 4 (lâminas). Os níveis de nitrogênio corresponderam a 0; 200 e 400 kg ha-1 ano-1 de N, aplicados por meio de fertirrigações semanais. As lâminas de irrigação foram equivalentes a 0; 50; 100 e 120% da evapotranspiração de referência (Eto), determinada em função de tanque classe A. A produção de palmito por planta foi avaliada dos 30 aos 34 meses após o plantio. Houve efeito significativo dos tratamentos (irrigação e adubação) para todas as variáveis relacionadas à produção. Os tratamentos com menores lâminas e doses de nitrogênio apresentaram as menores produções. Levando-se em conta o crescimento da planta e a produção de palmito, os resultados indicam que irrigação com 100% da ETo e fertirrigação com 200 kg ha-1 ano-1 de N são as recomendadas para a pupunheira cultivada em condições de solo, clima e manejo cultural semelhantes às deste estudo.

Nitrogen in Desert Grasses as Affected by Biosolids, their Time of Application, and Soil Water Content

This study evaluated the interactive effect of biosolids, time of application, and soil water on plant N concentration and uptake by Bouteloua gracilis (blue grama) and Hilaria mutica (tobosagrass) grown in pots. Biosolids were surface-applied to the soil of the pots either in the spring or the summer at rates of 0, 7, 18, 34, and 90 dry Mg ha−1. All of the pots were irrigated weekly to achieve 40% or 80% of field capacity soil water. The maximum increase in B. gracilis tissue N concentration due to biosolids application with respect to control was 41% in plants grown under the higher irrigation regime and only 15% in those plants grown under the lower irrigation regime. In H. mutica, the higher irrigation level produced an average of 20% higher tissue N concentration than the lower irrigation level across all biosolids application rates. Both species had a much higher N uptake (3.5- to 6.3-fold) under the higher than under the lower irrigation regime due to the large increase in shoot biomass caused by the higher irrigation level, regardless of rate of biosolids. At low biosolids rates, soil NO3 −-N was higher under the lower irrigation regime than under the higher irrigation regime due to the lower N uptake in plants. Spring application of biosolids produced higher soil NO3 −-N levels than summer application only when irrigation level was high. The fertilizing effect of biosolids depended heavily on soil water availability.

Impact of drip and surface irrigation on growth, yield and WUE of capsicum ( Capsicum annum L.)

A study was conducted to understand the effect of different irrigation methods and schedules on morphological, biophysical, yield and water use efficiency (WUE) of capsicum ( Capsicum annum L.) var. California Wonder. The plants grown under drip irrigation had more number of branches and plant heights compared to that of surface irrigated plants. The total yield was less at lower levels of irrigation. Above ground matter that included stem and leaf dry weight had positive correlation with yield under drip (0.992 ∗∗) and surface irrigation (0.926 ∗∗). The carbon dioxide exchange rates varied considerably under different methods of irrigation due to difference in irrigation timings and quantity of water applied. A shift in photosynthetic mechanism was observed in plants under IW/CPE 1.0 treatment. The relationship of WUE and net photosynthesis was also studied. The yield was found to have significant positive correlation with total dry matter (TDM, 0.865 ∗∗) and net photosynthesis (0.840 ∗∗). Any factor that could bring in a change in net photosynthesis and TDM may cause variation in yield in capsicum. Root mass was more in surface irrigated crop where as total root length was more in drip irrigated crop. As the quantity of water applied increased the root finesses decreased. Thus drip irrigation at 100% CPE is beneficial for capsicum plant in terms of yield, better plant morphological characters, viz. plant height number of branches, root finesses and root length, etc.

Growth, dry-matter partitioning and yiel of sweet potato (Ipomoea batatas L.) as influenced by soil mechanical impedance and mineral nutrition under different irrigation regimes.

Sweet potato plants were grown under different irrigation regimes ranging from IW/CPE ratio 1.5, 1.2, 0.9, 0.6, 0.3 as well as rainfed control. At lower irrigation level, mechanical resistance of soil restricted tuber bulking as well as significantly reduced tuber yield (r= -0.8712*). Irrigation increased uptake of both N and K compared to rainfed control. While at lower irrigation more soil resistance restricted growth and tuber development, at higher irrigation more labile N as well as K favored more vegetative growth reducing tuber dry matter production and tuber yield. However, the higher uptake of both N and K was observed at IW/CPE ratio 0.9, which also showed highest yield. The significant association of both dry matter production rate (r= 0.9586**) and total biomass (0,9820**) and non-significant association of harvest index (r= 0.6956) with tuber yield suggested more importance of dry-matter production than partitioning of dry matter in determining tuber yield in sweet potato under different moisture regime.