Strategies for increasing sustainability of wheat (Triticum aestivum L.) and faba bean (Vicia faba L.) production : effect of composts, rotation and biofertilizers

Abstract

An increasing human population poses extraordinary challenges on agricultural production. Feeding an estimated 10 billion people by 2050 requires more food with good nutritious value. Synthetic fertilizers and herbicides have been heavily used in many parts of the world to enhance crop yield and double food production, while poor farmers of, e.g., Sub-Saharan Africa apply little or no fertilizer due to its cost. Longterm and unbalanced applications of inorganic fertilizers, as well as lack of fertilization have degraded soil quality in many areas. Therefore, introducing a sustainable way of crop production without deteriorating soil quality at minimum cost to supply quality food to the world, including the poorest, is mandatory. Applying organic fertilizers such as different compost types, applying biofertilizers, and using crop rotation with legumes may increase yields, yield quality, and soil quality. However, systematic approaches to comparing the effect of composts derived from different composting techniques alone or combined with different biofertilizers or mineral fertilizers, and a rotation with legumes are scarce. Therefore, the objectives of the present study were to evaluate the effects of different compost types, biofertilizers and rotation on wheat and faba bean yield, crop nutrient content, economic return and soil quality indicators. Two years of field experiments and a supporting mineralization study were conducted in order to evaluate Objectives I up to IV, presented in Papers I, II, and III. A greenhouse experiment was conducted to evaluate the Objectives V and VI (presented in the synopsis). A one-season field experiment evaluated the effect of traditional compost, vermicompost, and material composted with additional effective microorganisms (EM) on faba bean yield and related properties. The composts were applied at three nitrogen (N) levels (18, 27, and 36 kg N ha -1) and compared to mineral fertilizer alone, or a combination of compost and mineral fertilizer. All three compost types resulted in a higher grain and biomass yield, as well as nutrient uptake into grain, compared to mineral fertilizer. This was reflected in a higher number of nodules and higher residual soil N in the compost treatments. Among the compost types, EM and vermicompost were most efficient, with a yield of approximately 3.6 and 3.45 t ha -1, respectively, compared to traditional compost with a yield of 3.1 t ha -1. Similar results were found for the other investigated properties. A two-year field experiment was carried out to evaluate the effects of traditional compost, vermicompost, and compost with effective microorganisms (EM) in combination with crop rotation, on wheat yield and grain nutrient concentration. The compost treatments were applied at three N levels (i.e., 32, 64, and 96 kg N ha-1) and compared to mineral fertilizer alone or to a combination of compost and mineral fertilizer in a randomized complete block design. All three composts, both alone and combined with mineral fertilizer, resulted in a higher grain yield than the equivalent mineral fertilizer level. However, the combined treatments with EM compost (5377 kg ha-1) and vermicompost (5324 kg ha-1) with mineral fertilizer in the second season resulted in the highest yields. Wheat rotation with faba bean also led to higher grain yields and nutrient concentrations than continuous wheat production. EM and vermicompost application combined with mineral fertilizer in the faba bean rotation resulted in the highest grain concentrations of N, phosphorus (P), sulphur (S), zinc (Zn) and iron (Fe). Furthermore, application of compost with effective microorganisms and vermicompost improved soil physical, chemical, and biological indicators, i.e., increasing the number of macroaggregates, total N, plant-available P, cation exchange capacity, labile carbon, microbial biomass, soil respiration; and decreasing the number of microaggregates, bulk density and pH compared to traditional compost at the same rate of N application. The combined application of EM compost or vermicompost with mineral fertilizer, respectively, improved physical, chemical, and biological indicators compared to compost or mineral fertilizer alone. In addition, the soil quality indicators were improved by rotation with the faba bean compared to continuous wheat. The economic analysis showed that EM compost application at medium (27 kg ha-1) and high (36 kg ha-1) N level and in the combined treatment (18 kg N ha-1 compost + 18 kg N ha-1 mineral fertilizer) were the most profitable treatments in the faba bean crop, with marginal rates of return varying between approximately 790 and 2800 %. In the wheat crop, EM compost and vermicompost application in the combined treatments (32 kg N ha-1 compost + 32 kg N ha-1 mineral fertilizer) and at high (96 kg ha-1) N level were the most profitable among the treatments, with marginal rates of return varying between 173 and 29530 %. A greenhouse experiment evaluated the effect of compost or mineral fertilizer with co-inoculation or single inoculation of Azotobacter chroococcum and Bacillus polymyxa on wheat and the integrated effect of compost or mineral fertilizer with single inoculation of Rhizobium leguminosarum or co-inoculation of Rhizobium leguminosarum and Bacillus polymyxa on faba bean. Co-inoculation of P-solubilizing bacteria and N-fixing bacteria combined with compost or mineral fertilizer improved both wheat and faba bean grain yield and nutrient uptake. The overall conclusion from this study is that the application of EM and vermicompost combined with mineral fertilizer integrated with crop rotation, improved wheat and faba bean production sustainably by improving yield, crop nutrient content and soil quality indicators at a relatively low cost. When these composts were combined with application of biofertilizers, the grain yield and nutrient absorption could be further improved.

Den raskt økende befolkningstilveksten gir en ekstraordinær utfordring for den globale matproduksjonen. Å mette en anslått befolkning på 10 milliarder mennesker innen 2050 krever høyere produksjon, og maten som produseres må ha god næringsverdi. Mineralgjødsel og ugressmidler er blitt mye brukt i store deler av verden for å øke avlinger og matproduksjonen, mens fattige bønder, bønder for eksempel i Afrika sør for Sahara, har ikke hatt tilgang til og dermed heller ikke brukt, eller brukt lite mineralgjødsel på grunn av de høye kostnadene. Langsiktig og ubalansert tilførsel av uorganisk gjødsel, samt mangel på gjødsling, har forringet kvaliteten og utarmet jorda mange steder i verden. Derfor er det viktig å sørge for at planteproduksjon framover skal utføres bærekraftig, uten forringelse av jordkvaliteten og med et minimum av kostnader, slik at kvalitetsmat kan leveres til en hel verden, inkludert de fattigste. Bruk av organisk gjødsel basert på forskjellige komposttyper, mikroorganismer som øker tilgjengeligheten av næringsstoffer i rhizosfæren og vekstskifte med belgfrukter, kan ha potensiale til å øke avlingene, samt jord- og avlingskvaliteten. En systematisk tilnærming hvor effekten av kompost, fra ulike komposttyper alene eller kombinert med ulike mikroorganismer eller mineralgjødsel, og i omløp med belgvekster, mangler. Formålet med denne studien var derfor å analysere effekten av ulike komposttyper, bruk av mikroorganismer som øker tilgjengeligheten av næringsstoffer i rhizosfæren og vekstskifte med en belgvekst på avling av hvete og fababønne, næringsinnhold i avlingen, økonomisk avkastning og jordkvalitet.