Mirasol F. Pampolino

Experimental validation of a new approach for rice fertiliser recommendations across smallholder farms in China

Inappropriate fertiliser applications have caused a series of environmental problems and threaten the sustainable production of rice in China. The aim of this study was to evaluate the effects of a new approach, Nutrient Expert (NE), a nutrient decision support tool for rice (Oryza sativa L.). Experimental validation was carried out under field conditions from 2013 to 2015 at 211 sites in the main rice-growing regions of China. The results showed that, compared with current farmers’ fertiliser practices (FP) and soil testing (ST), the NE approach balanced nutrient application – decreased the nitrogen (N) and potassium (K) rates, and increased the phosphorus (P) rate – and improved grain yield, nutrient uptake, and fertiliser use efficiency. The NE treatment produced a 3.5–6.3% higher grain yield, 2.3–14.2% higher N, P, and K uptake in aboveground plant dry matter, and higher agronomic efficiency, apparent recovery efficiency (RE), and partial factor productivity of applied N and K, but not for P. In particular, the RE of the NE approach was greater by 12.2 and 8.4 percentage points for N, 3.7 and 2.9 percentage points for P, and 16.3 and 6.4 percentage points for K, compared with FP and ST respectively. The results obtained from field validation suggested that the NE approach could predict target yields; nutrient uptake of N, P, and K within specific ranges; and could be used as a tool to make fertiliser recommendation for rice in China.

Estimating nutrient uptake requirements for soybean using QUEFTS model in China

Estimating balanced nutrient requirements for soybean (Glycine max [L.] Merr) in China is essential for identifying optimal fertilizer application regimes to increase soybean yield and nutrient use efficiency. We collected datasets from field experiments in major soybean planting regions of China between 2001 and 2015 to assess the relationship between soybean seed yield and nutrient uptake, and to estimate nitrogen (N), phosphorus (P), and potassium (K) requirements for a target yield of soybean using the quantitative evaluation of the fertility of tropical soils (QUEFTS) model. The QUEFTS model predicted a linear–parabolic–plateau curve for the balanced nutrient uptake with a target yield increased from 3.0 to 6.0 t ha−1 and the linear part was continuing until the yield reached about 60–70% of the potential yield. To produce 1000 kg seed of soybean in China, 55.4 kg N, 7.9 kg P, and 20.1 kg K (N:P:K = 7:1:2.5) were required in the above-ground parts, and the corresponding internal efficiencies (IE, kg seed yield per kg nutrient uptake) were 18.1, 126.6, and 49.8 kg seed per kg N, P, and K, respectively. The QUEFTS model also simulated that a balanced N, P, and K removal by seed which were 48.3, 5.9, and 12.2 kg per 1000 kg seed, respectively, accounting for 87.1%, 74.1%, and 60.8% of the total above-ground parts, respectively. These results were conducive to make fertilizer recommendations that improve the seed yield of soybean and avoid excessive or deficient nutrient supplies. Field validation indicated that the QUEFTS model could be used to estimate nutrient requirements which help develop fertilizer recommendations for soybean.