Adaption to rainfall and temperature variability through integration of mungbean in maize cropping

Climate change has threatened global agricultural activities, particularly in tropical and subtropical regions. Rainfed cropping regions have become under more intense risk of crop yield loss and crop failure, especially in upland areas which are also prone to soil erosion. In Thailand, maize is one of the important economic crops and mostly grown in upland areas of northern regions. Maize yield productivity largely depends on the onset of seasonal rainfall. Uncertainty of seasonal rainfall adversely affects maize yield productivity. Therefore, coping strategies are urgently needed to stabilize maize yields under climate variability. In order to identify suitable coping strategies, early maize sowing and maize and mungbean relay cropping were tested on upland fields of northern Thailand. The specific aims of this thesis were (i) monitoring growth and yield performance of maize and mungbean under relay cropping, (ii) testing early maize sowing and maize mungbean relay cropping as coping strategies under rainfall variations (Chapter 2), (iii) testing effects of relay cropping on growth and yield of mungbean under weather variability (Chapter 4), (iv) determining suitable sowing dates under erratic rainfall patterns by using a modelling approach (Chapter 3), and (v) developing a technique for diagnosis of crop water stress in maize by thermal imaging technique (Chapter 5). Specifically, in Chapter 2 early maize planting or relay cropping strategies were assessed for growth and yield performance of maize under heat and drought conditions. Maize planted in July showed, regardless of sole or relay cropping, low grain formation as a consequence of adverse weather conditions during generative growth. However, July-planted maize relay cropping produced higher above ground biomass than July-planted maize sole cropping and early planting of maize in June. Despite unfavourable weather conditions, maize was, at least partly, able to compensate for such effects when relayed cropped, achieving a higher yield compared to maize sole cropping. June-planted maize sole cropping, however, was fully able to escape such a critical phase and achieved the highest grain yield (8.5 Mg ha-1); however, its associated risk with insufficient rain after early rain spells needs to be considered. Relay cropping showed to be an alternative coping strategy to cope with extreme weather as compared to maize sole cropping. However, relay cropping reduced maize growth due to light competition at young stages of maize before mungbean was harvested (Chapter 2). This negative impact of relay cropping is partly off-set by considering of land equivalent ratio (Chapter 4). Land equivalent ratio indicated a beneficial effect of relay cropping over maize and mungbean solecropping (LER = 2.26). During high precipitation, mungbean sole cropping produced higher yield (1.3 Mg ha-1) than mungbean relay cropping (0.7 Mg ha-1). In contrast to the period of low precipitation, mungbean relay cropping used available water more efficiently and was able to establish its plant, while mungbean sole cropping could not fully withstand severe drought and heat. Mulching effects of maize residues conserved soil water which was then available for mungbean to grow under extreme weather condition. WaNuLCAS modelling approaches can be used to support the decision of maize sowing date in northern Thailand to cope with climate change as indicated by goodness of fit of the model validation (R2 = 0.83, EF = -0.61, RMSE = 0.14, ME = 0.16, CRM = 0.02 and CD = 0.56) (Chapter 3) using forty-eight-year of historical rainfall patterns of Phitsanulok province. Only 27.1% of rainfall probability was classified as a normal rainfall condition. Consequently, maize in this region had faced with high rainfall variability. From long term simulation runs, the current maize sowing date led to strong maize yield variation depending on rainfall condition. Early maize sowing i.e. 15 and 30 days before farmers and staggered planting produced higher yield than current farmers practice (mid of July) in most conditions (91.7%). Simulations revealed that water was the most limiting factor affecting maize growth and yield while nutrients (N and P) had only limited impact. Results of the WaNuLCAS model could be used to identify optimal maize planting date in the area prone to soil erosion and climate variation of northern Thailand; however, the model cannot fully account for heat stress. Thermal imaging technique is a useful method for diagnose maize water status. As presented in chapter 5, the developed Crop Water Stress Index (CWSI) using a new approach of wet/dry references revealed a strong relationship between CWSI and stomatal conductance (R2 = 0.82). Our study results established a linear relationship to predict final maize grain yield and CWSI values at 55 DAS as follows Yield = -16.05×CWSI55DAS + 9.646. Both early planting of maize and/or relay cropping with legumes are suitable coping strategies for rainfall variability prone regions. The positive response of early planting and legume relay cropping offers the opportunity of having a short-duration crop as sequential crop, providing an additional source of protein for humans and fostering crop diversification on-site. This leads to a win-win situation for farmers, food security and the environment due to an enhanced sustainability of this cropping system.Der Klimawandel bedroht die Landwirtschaft weltweit, besonders aber in tropischen und subtropischen Regionen. Im Regenfeldbau steigt das Risiko von Ertragsverlusten und Ernteausfällen, insbesondere in Bergregionen, die auch anfällig für Bodenerosion sind. In Thailand ist Mais eine der wichtigsten wirtschaftlichen Nutzpflanzen und wird hauptsächlich in den Hochlandgebieten in Norden des Landes angebaut. Die Produktivität des Maisertrags hängt weitgehend vom Einsetzen der saisonalen Regenfälle ab. Die Unsicherheit der saisonalen Niederschläge wirkt sich negativ auf die Produktivität von Mais aus. Daher werden dringend Strategien benötigt, um die Maiserträge unter Klimaschwankungen zu stabilisieren. Um geeignete Strategien zu identifizieren, wurden auf Hochlandfeldern in Nordthailand eine frühe Maisaussaat und ein Mais- und Mungbohnen-Staffelanbau getestet. Die spezifischen Ziele dieser Arbeit waren (i) die Beobachtung des Wachstums und der Ertragsleistung von Mais und Mungbohnen unter Staffelanbau, (ii) die Prüfung der frühen Maisaussaat und des Mais-Mungbohnen-Staffelanbaus als Strategien zur Stressvermeidung bei Niederschlagsschwankungen (Kapitel 2), (iii) das Testen der Auswirkungen von Staffelanbau auf das Wachstum und den Ertrag von Mungbohnen unter schwankenden Wetterbedingungen (Kapitel 4), (iv) Bestimmung geeigneter Aussaattermine unter erratischen Niederschlagsmustern mit Hilfe eines Modellierungsansatzes (Kapitel 3) und (v) Entwicklung einer Technik zur Diagnose von Wasserstress bei Mais mit Hilfe von Wärmebildtechnik (Kapitel 5). In Kapitel 2 wurden insbesondere die Strategien der frühen Maisaussaat oder des Mais- und Mungbohnen-Staffelanbaus auf die Wachstums- und Ertragsleistung von Mais unter Hitze und Trockenheit untersucht. Mais, der im Juli gepflanzt wurde, zeigte, unabhängig vom Reinanbau oder des Staffelanbaus mit Mungbohnen, eine geringere Kornbildung als Folge ungünstiger Wetterbedingungen während des generativen Wachstums. Allerdings erzeugte der im Juli gepflanzte Mais-Mungbohnen-Staffelanbau eine höhere oberirdische Biomasse als die im Juli gepflanzte Maismonokultur und die frühe Pflanzung von Mais im Juni. Trotz ungünstiger Witterungsbedingungen konnte der Mais im Staffelanbau mit Mungbohnen negative Effekte zumindest teilweise kompensieren und erzielte einen höheren Ertrag im Vergleich zum Juli gesäten Maisreinanbau. Der im Juni gesäte Maisreinanbau konnte sich jedoch einer solchen kritischen Phase vollständig entziehen und erzielte daher den höchsten Kornertrag (8,5 Mg ha-1);allerdings muss das damit verbundene Risiko unzureichender Regenfälle nach frühen Regenperioden berücksichtigt werden. Der Staffelanbau von Mais und Mungbohnen erwies sich als eine sinnvolle Alternative bei extremen Witterungsbedingungen im Vergleich zum Maisreinanbau. Allerdings reduzierte dieser das Wachstum von Mais aufgrund von Lichtkonkurrenz in frühen Wachstumsstadien des Mais vor der Ernte der Mungbohnen (Kapitel 2). Diese negative Auswirkung wird teilweise durch die Berücksichtigung des Flächenäquivalenzverhältnisses (im Englischen mit LER abgekürzt) ausgeglichen (Kapitel 4). Der LER-Wert zeigte einen positiven Effekt des Staffelanbaus gegenüber dem Mais- und Mungbohnenreinanbaus (LER = 2,26). Bei hohen Niederschlägen brachte der Mungbohnen-Alleinanbau höhere Erträge (1,3 Mg ha-1) als der Mungbohnen- Staffelanbau (0,7 Mg ha-1). Im Gegensatz zur Periode mit geringen Niederschlägen nutzte der Mungbohnen-Staffelanbau das verfügbare Wasser effizienter und konnte seine Pflanze etablieren, während der Mungbohnen-Alleinanbau schwerer Trockenheit und Hitze nicht vollständig standhalten konnte. Die Mulchwirkung von Maisresten konservierte das Bodenwasser, das dann für das Wachstum der Mungbohnen unter den extremen Wetterbedingungen zur Verfügung stand. Die Modellierung der getesteten Systeme mit WaNuLCAS kann verwendet werden, um die Entscheidung über den Zeitpunkt der Maisaussaat in Nordthailand zu unterstützen, um mit dem Klimawandel fertig zu werden, wie die Validierung des Models (R2 = 0,83, EF = -0,61, RMSE = 0,14, ME = 0,16, CRM = 0,02 und CD = 0,56) (Kapitel 4) unter Verwendung von historischen Niederschlagsdaten (1970-2018) der Provinz Phitsanulok zeigt. Lediglich 27,1 % der jährlcihen Niederschläge wurde als normale Niederschlagsbedingung eingestuft. Folglich war der Mais in dieser Region mit einer hohen Niederschlagsvariabilität konfrontiert. Aus den Langzeitsimulationsläufen ging hervor, dass der aktuelle Maisaussaattermin zu starken Schwankungen des Maisertrags in Abhängigkeit von den Niederschlagsbedingungen führte. Eine frühe Maisaussaat, d.h. 15 und 30 Tage vor der Aussaat, und eine gestaffelte Aussaat führten unter den meisten Bedingungen zu höheren Erträgen als die derzeitige Praxis der Landwirte (Aussaat Mitte Juli) (91,7%). Die Simulationen zeigten, dass Wasser der am meisten begrenzende Faktor für das Wachstum und den Ertrag von Mais war, während Nährstoffe (N und P) nur einen begrenzten Einfluss hatten. Die Simulationen des WaNuLCAS-Modells können zur Bestimmung des optimalen Maispflanzdatums in für Bodenerosion und Klimaschwankungen anfälligenGebieten Nordthailands zur Prognose und Testen optimaler Saattermine verwendet werden; allerdings kann das Modell den Hitzestress nicht vollständig berücksichtigen. Die Wärmebildtechnik ist eine nützliche Methode zur Diagnose des Wasserstatus von Mais. Wie in Kapitel 5 dargestellt, zeigte der entwickelte Pflanzen-Wasserstress Index (im Englischen CWSI) unter Verwendung eines neuen Ansatzes von Nass/Trockenreferenzen eine starke Beziehung zwischen CWSI und stomatärer Leitfähigkeit (R2 = 0,82). Die Ergebnisse dieser Arbeit ergaben eine lineare Beziehung zur Vorhersage des endgültigen Maiskornertrags und der CWSI-Werte basierend auf Daten die 55 Tage nach der Aussaat(im Englischen DAS) erhoben wurden. Die Gleichung lautet "Ertrag = -16,05×CWSI55DAS + 9,646". Daraus kann gefolgert werden, dass sowohl die frühe Aussaat von Mais als auch der Staffelanbau mit Leguminosen für Regionen, die von Niederschlagsschwankungen betroffen sind, sich als Strategien zur Vermeidung von Stress im Maisanbau eignen. Die positive Reaktion auf die frühe Aussaat und den Leguminosen-Staffelanbau bietet die Möglichkeit, eine kurzlebige Kultur als Zweitkultur im Maisanbau zu etablieren, die eine zusätzliche Proteinquelle für den Menschen darstellt und die Anbaudiversifizierung vor Ort fördert. Dies führt zu einer Win-Win-Situation für die Landwirte, die Ernährungssicherheit und die Umwelt, da die Nachhaltigkeit des Anbausystems Maisanbaus verbessert wird

Early planting and relay cropping: pathways to cope with heat and drought?

Maize (Zea mays) is an important food and cash crop of uplands in Southeast Asia, where it is often prone to drought and heat stress associated with climate change. This study aimed at assessing the effect of heat and drought on maize performance, testing coping strategies under such weather extremes, and understanding associated mechanisms. The experiment was carried out during 2018 in Thailand, using a split-plot design with three replications. Treatments were: July-planted maize sole cropping (control), July-planted maize-mungbean (Vigna radiata) relay cropping, and June-planted maize sole cropping. High temperatures and dry spells during July-August 2018 decreased maize growth strongest in the control and less so in maize relay cropping during generative growth stages, but not in June-planted maize sole cropping. Stress reduced maize nitrogen nutrition index by 40%. Relay-cropped maize had a significantly higher potential to keep stomata open (320 mmol m-2 s-1) than sole-cropped maize (100 mmol m-2 s-1). Δ13C of maize grains confirmed that June-planted maize (‑9.43‰) was less affected by dry spells and heat stress than July-planted sole cropped maize (‑10.23‰). Under relay cropping, the latter showed less water stress (δ13C: ‑10.12‰) compared to sole cropping and a higher soil water use. Maize was better able to cope with heat and drought stress when relayed-cropped, although less compared to early-planting of maize. Hence, the tested coping strategies are able to mitigate heat and drought effects on maize growth, while improving food security and crop diversification when relay-cropped with mungbeans

Dynamics of soil nitrogen availability following conversion of natural forests to various coffee cropping systems in northern Thailand

Land conversion critically affects soil physiochemical and biological properties, yet very little remains clear about the impact of forest conversion on the N pool and related microbial N transformations. Therefore, this study aimed to examine the dynamics of soil N availability following forest conversion into the different coffee cropping systems, and explore the mechanisms behind these dynamics from the microbial N transformation. Disturbed soil samples from two depths (0–20 and 20–40 cm) were collected from four land uses consisting of three different coffee cropping systems (coffee monocultures (C), coffee agroforestry (FC), coffee associated with persimmon (Diospyros kaki L.) (CH)) converted from natural forest and adjacent natural forest (F) in northern Thailand. The soil labile N pools (including ammonium (NH4+), nitrate (NO3−), inorganic N (IN), dissolved organic N (DON) contents and microbial biomass N (MBN)) were measured, as well as the soil total N (STN) content. Soil N transformation rates, including net N mineralization, nitrification, and immobilization, were determined using a laboratory incubation experiment. The results showed that the forest conversion to coffee agroforestry significantly increased soil N content by 39.83 % in topsoil, but no significant difference was observed in C and CH soils as compared to F soil (p ≤ 0.05). The three labile N forms (NH4+, NO3− and DON content) were significantly higher under the C, FC and CH soils in both depths, while the coffee monoculture decreased the MBN content. The increases in soil IN, IN/DON and NO3−/NH4+ ratios used as an N availability indicator were positively associated with an increase in the N mineralization and nitrification processes following the forest conversion. Interestingly, the N immobilization processes in the F and FC soils were significantly higher than those in the C and CH soils, which indirectly regulated a decreased nitrification rate in F and FC soils in our study. With the exception of the FC soil, the nitrification/N immobilization ratios in the C (4.95) and CH (4.08) soils were higher than those in the F (0.70) soil, indicating an increased N loss risk after forest conversion. Therefore, coffee agroforestry systems have the potential to be effective management strategies for improving soil nitrogen sequestration following forest conversion

Efficacy of Different Routes of Formalin-Killed Vaccine Administration on Immunity and Disease Resistance of Nile Tilapia (<i>Oreochromis niloticus</i>) Challenged with <i>Streptococcus agalactiae</i>

Vaccines prepared from formalin-killed Streptococcus agalactiae were administered to Nile tilapia (Oreochromis niloticus) via three different routes: immersion in a water-based vaccine, injection with an oil-based vaccine, and as a water-based oral vaccine. All vaccination treatments increased lysozyme and peroxidase activity in skin mucus of Nile tilapia by 1.2- to 1.5-fold compared to their activities in unvaccinated control fish. Likewise, alternative complement, phagocytosis, and respiratory burst activities in the blood serum of the vaccinated fish were 1.2- to 1.5-times higher than in the unvaccinated fish. In addition, the expression transcripts of interleukin-1 (IL-1), interleukin-8 (IL-8), and lipopolysaccharide-binding protein (LBP) were 2.3- to 2.9-fold higher in the vaccinated fish compared to those in the unvaccinated control. The unvaccinated fish challenged with Streptococcus agalactiae had a survival rate of 25% compared to a survival rate of 78–85% for the vaccinated fish. The differences between the unvaccinated and vaccinated fish were all statistically significant, but there was no significant difference in any of the indicators of immunity between the three vaccinated groups. Collectively, these results confirm that vaccination with formalin-killed Streptococcus agalactiae significantly improved the resistance of Nile tilapia to infection by the pathogen. Overall, the efficacy of oral administration of the vaccine was comparable to that of vaccine administered via injection, indicating that oral vaccination is a viable cost-effective alternative to administering vaccines by injection

Efficacy of Different Routes of Formalin-Killed Vaccine Administration on Immunity and Disease Resistance of Nile Tilapia (Oreochromis niloticus) Challenged with Streptococcus agalactiae

Vaccines prepared from formalin-killed Streptococcus agalactiae were administered to Nile tilapia (Oreochromis niloticus) via three different routes: immersion in a water-based vaccine, injection with an oil-based vaccine, and as a water-based oral vaccine. All vaccination treatments increased lysozyme and peroxidase activity in skin mucus of Nile tilapia by 1.2- to 1.5-fold compared to their activities in unvaccinated control fish. Likewise, alternative complement, phagocytosis, and respiratory burst activities in the blood serum of the vaccinated fish were 1.2- to 1.5-times higher than in the unvaccinated fish. In addition, the expression transcripts of interleukin-1 (IL-1), interleukin-8 (IL-8), and lipopolysaccharide-binding protein (LBP) were 2.3- to 2.9-fold higher in the vaccinated fish compared to those in the unvaccinated control. The unvaccinated fish challenged with Streptococcus agalactiae had a survival rate of 25% compared to a survival rate of 78&ndash;85% for the vaccinated fish. The differences between the unvaccinated and vaccinated fish were all statistically significant, but there was no significant difference in any of the indicators of immunity between the three vaccinated groups. Collectively, these results confirm that vaccination with formalin-killed Streptococcus agalactiae significantly improved the resistance of Nile tilapia to infection by the pathogen. Overall, the efficacy of oral administration of the vaccine was comparable to that of vaccine administered via injection, indicating that oral vaccination is a viable cost-effective alternative to administering vaccines by injection