Imbalanced application of nitrogen(N) and phosphorus(P) fertilizers can result in reduced crop yield,low nutrient use efficiency,and high loss of nutrients and soil nitrate nitrogen(NO_3^--N) accumulation decreases when N is applied with P and/or manure;however,the effect of applications of N with P and/or manure on root growth and distribution in the soil profile is not fully understood.The aim of this study was to investigate the combined effects of different N and P fertilizer application rates with or without manure on maize(Zea mays L.) yield,N uptake,root growth,apparent N surplus,Olsen-P concentration,and mineral N(N_(min)) accumulation in a fluvo-aquic calcareous soil from a long-term(28-year) experiment.The experiment comprised twelve combinations of chemical N and P fertilizers,either with or without chicken manure,as treatments in four replicates.The yield of maize grain was 82%higher,the N uptake 100%higher,and the N_(min) accumulation 39%lower in the treatments with combined N and P in comparison to N fertilizer only.The maize root length density in the 30-60 cm layer was three times greater in the treatments with N and P fertilizers than with N fertilizer only.Manure addition increased maize yield by 50%and N uptake by 43%,and reduced N_(min)(mostly NO_3^--N) accumulation in the soil by 46%.The long-term application of manure and P fertilizer resulted in significant increases in soil Olsen-P concentration when no N fertilizer was applied.Manure application reduced the apparent N surplus for all treatments.These results suggest that combined N and P fertilizer applications could enhance maize grain yield and nutrient uptake via stimulating root growth,leading to reduced accumulation of potentially leachable NO_3^--N in soil,and manure application was a practical way to improve degraded soils in China and the rest of the world.
Overuse of fertilizers and the resultant pollution and eutrophication of surface and groundwater is a growing issue in China.Consequently, improved management strategies are needed to optimize crop production with reduced nutrient inputs. Conventional fertilization(CF), reduced fertilization(RF), and reduced fertilization with maize(Zea mays L.) as a summer catch crop(RF+C)treatments were evaluated in 2008 and 2009 by quantifying tomato(Lycopersicon esculentum) fruit yield and soil nutrient balance in a greenhouse tomato double-cropping system. Fertilizer nitrogen(N) application was reduced by 37% in the RF and RF+C treatments compared to the CF treatment with no significant reduction in fruit yield. Mean soil mineral N(Nmin) content to a depth of 180 cm following tomato and maize harvest was lower in the RF and RF+C treatments than in the CF treatment. Residual soil Nmincontent was reduced by 21% and 55% in the RF and RF+C treatments, respectively, compared to the CF treatment. Surplus phosphorus(P)and potassium(K) contents in the RF+C treatment were significantly lower than those in the RF treatment, mainly due to additional P and K uptake by the catch crop. We concluded that for intensive greenhouse production systems, the RF and RF+C treatments could maintain tomato fruit yield, reduce the potential for nitrate(NO-3-N) leaching, and with a catch crop, provide additional benefits through increased biomass production.
