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The present investigation aimed at evaluating the effect of Calliandra calothyrsus Meisn green manure on the quality improvement of maize (Zea mays L.) stover compost. To that end, two field experiments were installed with maize (Zea mays L.) and a successive potato (Solanum tuberosum L.) crop, which was specifically set up to investigate the potential residual effects of tested organo-mineral fertilizers. The potato (Solanum tuberosum L.) crop did not receive any fertilizer, either organic or mineral. The experimental design was a randomized complete block with three replicates. The basic experimental plot was 1.6 m wide and 3 m long (4.8 m²). Treatments under evaluation were: T1=Control, T2=Maize stover co-composted with mineral fertilizer, T3=Maize stover co-compost with Calliandra calothyrsus Meisn green manure; T4=Farm manure+45-60-30; and T5=Maize stover co-composted with Calliandra calothyrsus Meisn green manure+45-60-30. Evaluated parameters were grain yields, root biomass, above-ground biomass, Harvest Index, and Root/Shoot ratio for maize (Zea mays L.). Potato yields were categorized into small size (< 35 mm), medium size (35-65 mm) and big size tubers (> 65 mm). Significant effects (p < 0.001) of tested fertilizer treatments were observed for maize grain yields (GY), above-ground biomass (AGB), and root biomass (RB). No effect (p > 0.05) of fertilizer treatments could be noticed on the harvest index (HI=0.31-0.38) or R/S ratio (0.079-0.088). For the successive potato crop, a significant effect (p < 0.001) of tested treatments was only observed for the seed-oriented medium size tubers (MST) potato yield. Overall, the most relevant observation of the maize experiment is that treatments T4 and T5 gave higher and equivalent grain and biomass yields. From there, we derive that maize stover co-composted with Calliandra calothyrsus Meisn green manure could be a sound substitute to farm manure. Additionally, the potato experiment highlighted the residual effects of the T3 treatment, statistically equivalent to that of T2. Consequently, we advise that the effects of compost-based organo-mineral fertilizers on crop yields should be evaluated beyond a single seasonal crop, in order to fully catch their residual fertilizer potentials.&nbsp

The present investigation highlights and compares the direct and residual fertilizer values of maize (Zea mays L.) stover composted with Calliandra calothyrsus Meisn and Tithonia diversifolia (Hemsl.) A. Gray-green manure on maize (Zea mays L.) and successive potato (Solanum tuberosum L.). Two field studies were installed with maize and successive potato crops in a completely randomized block design (CRBD) with three replicates. Statistical analyses were performed using R commander, version 4.0.2. Grain yields, root biomass, above ground biomass and calculated parameters (Root/Shoot ratio, Harvest Index and GinningRate) were evaluated for maize. Total potato yields were evaluated and categorized into small size tubers (SST < 35 mm) medium size tubers (MST: 35-65 mm) and big size tubers (BST > 65 mm). Treatments under evaluation were: T1=Control, T2=Farm (cow) manure alone, T3=Maize stover co-composted with Calliandra calothyrsus Meisn green manure; T4= Maize stover co-composted with Tithonia diversifolia (Hemsl.) A. Gray green manure; T5= Farm (cow) manure+45-60-30; T6= Maize stover co-composted with Calliandra calothyrsus Meisn green manure+45-60-30; T7=Maize stover co-composted with Tithonia diversifolia (Hemsl.) A. Gray green manure+45-60-30; and T8=Farm (cow) manure+FOMI Imbura+FOMI Totahaza. Obtained results indicated highest maize yields with FOMI organo-mineral fertilizers (2.7 T/ha) seconded by the recommended fertilizer practice T5 (2 T/ha). In the same line, highest R/S value (=0.38) was registered with the same FOMI treatment (T8), while the highest HI value (0.21) was observed with the maize stover co-composted with Tithonia diversifolia (Hemsl.) A. Gray (T4). Highest potato total yields were observed with the maize stover compost enriched with Tithonia diversifolia (Hemsl.) A. Gray and supplemented with mineral fertilizer (7.61 T/ha), followed by the same compost without mineral fertilizer addition (6.35 T/ha). We conclude our study with the following statements: i) the highest direct fertilizer value was observed with the FOMI treatment; ii) the residual fertilizer effects were more expressed with the maize stover co-composted with Tithonia diversifolia A. Gray green manure with or without mineral additive, followed by farm manure and maize stover enriched with Calliandra calothyrsus Meisn green manure. Consequently, we restate that the effects of compost-based organo-mineral fertilizers on crop yields should be definitely evaluated on a multiseasonal basis so as to fully capture their residual fertilizer potentials.